matrix_sdk_base/event_cache/store/

integration_tests.rs

// Copyright 2024 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Trait and macro of integration tests for `EventCacheStore` implementations.

use std::{
    collections::{BTreeMap, BTreeSet},
    sync::Arc,
};

use assert_matches::assert_matches;
use assert_matches2::assert_let;
use matrix_sdk_common::{
    deserialized_responses::{
        AlgorithmInfo, DecryptedRoomEvent, EncryptionInfo, TimelineEvent, TimelineEventKind,
        UnableToDecryptInfo, UnableToDecryptReason, VerificationState,
    },
    linked_chunk::{
        ChunkContent, ChunkIdentifier as CId, LinkedChunkId, Position, Update, lazy_loader,
    },
};
use matrix_sdk_test::{ALICE, DEFAULT_TEST_ROOM_ID, event_factory::EventFactory};
use ruma::{
    EventId, RoomId, event_id,
    events::{
        AnyMessageLikeEvent, AnyTimelineEvent, relation::RelationType,
        room::message::RoomMessageEventContentWithoutRelation,
    },
    push::Action,
    room_id,
};

use super::{
    super::{Gap, thread::ThreadInfo},
    DEFAULT_CHUNK_CAPACITY, DynEventCacheStore,
};
use crate::read_receipts::ReadReceipts;

/// Create a test event with all data filled, for testing that linked chunk
/// correctly stores event data.
///
/// Keep in sync with [`check_test_event`].
pub fn make_test_event(room_id: &RoomId, content: &str) -> TimelineEvent {
    make_test_event_with_event_id(room_id, content, None)
}

/// Create a `m.room.encrypted` test event with all data filled, for testing
/// that linked chunk correctly stores event data for encrypted events.
pub fn make_encrypted_test_event(room_id: &RoomId, session_id: &str) -> TimelineEvent {
    let device_id = "DEVICEID";
    let builder = EventFactory::new()
        .encrypted("", "curve_key", device_id, session_id)
        .room(room_id)
        .sender(*ALICE);

    let event = builder.into_raw();
    let utd_info = UnableToDecryptInfo {
        session_id: Some(session_id.to_owned()),
        reason: UnableToDecryptReason::MissingMegolmSession { withheld_code: None },
    };

    TimelineEvent::from_utd(event, utd_info)
}

/// Same as [`make_test_event`], with an extra event id.
pub fn make_test_event_with_event_id(
    room_id: &RoomId,
    content: &str,
    event_id: Option<&EventId>,
) -> TimelineEvent {
    let encryption_info = Arc::new(EncryptionInfo {
        sender: (*ALICE).into(),
        sender_device: None,
        forwarder: None,
        algorithm_info: AlgorithmInfo::MegolmV1AesSha2 {
            curve25519_key: "1337".to_owned(),
            sender_claimed_keys: Default::default(),
            session_id: Some("mysessionid9".to_owned()),
        },
        verification_state: VerificationState::Verified,
    });

    let mut builder = EventFactory::new().text_msg(content).room(room_id).sender(*ALICE);
    if let Some(event_id) = event_id {
        builder = builder.event_id(event_id);
    }
    let event = builder.into_raw();

    TimelineEvent::from_decrypted(
        DecryptedRoomEvent { event, encryption_info, unsigned_encryption_info: None },
        Some(vec![Action::Notify]),
    )
}

/// Check that an event created with [`make_test_event`] contains the expected
/// data.
///
/// Keep in sync with [`make_test_event`].
#[track_caller]
pub fn check_test_event(event: &TimelineEvent, text: &str) {
    // Check push actions.
    let actions = event.push_actions().unwrap();
    assert_eq!(actions.len(), 1);
    assert_matches!(&actions[0], Action::Notify);

    // Check content.
    assert_matches!(&event.kind, TimelineEventKind::Decrypted(d) => {
        // Check encryption fields.
        assert_eq!(d.encryption_info.sender, *ALICE);
        assert_matches!(&d.encryption_info.algorithm_info, AlgorithmInfo::MegolmV1AesSha2 { curve25519_key, .. } => {
            assert_eq!(curve25519_key, "1337");
        });

        // Check event.
        let deserialized = d.event.deserialize().unwrap();
        assert_matches!(deserialized, AnyTimelineEvent::MessageLike(AnyMessageLikeEvent::RoomMessage(msg)) => {
            assert_eq!(msg.as_original().unwrap().content.body(), text);
        });
    });
}

/// `EventCacheStore` integration tests.
///
/// This trait is not meant to be used directly, but will be used with the
/// `event_cache_store_integration_tests!` macro.
#[allow(async_fn_in_trait)]
pub trait EventCacheStoreIntegrationTests {
    /// Test handling updates to a linked chunk and reloading these updates from
    /// the store.
    async fn test_handle_updates_and_rebuild_linked_chunk(&self);

    /// Test that the next and previous fields only reference chunks that
    /// already exist in the store.
    async fn test_linked_chunk_exists_before_referenced(&self);

    /// Test that the same event can exist in a room's linked chunk and a
    /// thread's linked chunk simultaneously.
    async fn test_linked_chunk_allows_same_event_in_room_and_thread(&self);

    /// Test loading the last chunk in a linked chunk from the store.
    async fn test_load_last_chunk(&self);

    /// Test that cycles are detected when loading the last chunk in a linked
    /// chunk from the store.
    async fn test_load_last_chunk_with_a_cycle(&self);

    /// Test loading the previous chunk in a linked chunk from the store.
    async fn test_load_previous_chunk(&self);

    /// Test loading a linked chunk incrementally (chunk by chunk) from the
    /// store.
    async fn test_linked_chunk_incremental_loading(&self);

    /// Test removing a chunk.
    async fn test_linked_chunk_remove_chunk(&self);

    /// Test pushing items onto a linked chunk.
    async fn test_linked_chunk_push_items(&self);

    /// Test replacing an item in a linked chunk.
    async fn test_linked_chunk_replace_item(&self);

    /// Test remove an item from a linked chunk.
    async fn test_linked_chunk_remove_item(&self);

    /// Test detaching last items from a linked chunk.
    async fn test_linked_chunk_detach_last_items(&self);

    /// Test that start reattach and end reattach items does nothing.
    async fn test_linked_chunk_start_end_reattach_items(&self);

    /// Test clearing a linked chunk.
    async fn test_linked_chunk_clear(&self);

    /// Test clearing a linked chunk and re-inserting a past event.
    async fn test_linked_chunk_clear_and_reinsert(&self);

    /// Test that rebuilding a linked chunk from an empty store doesn't return
    /// anything.
    async fn test_rebuild_empty_linked_chunk(&self);

    /// Test that linked chunks are only accessible through their enclosing
    /// room.
    async fn test_linked_chunk_multiple_rooms(&self);

    /// Test that loading a linked chunk's metadata works as intended.
    async fn test_load_all_chunks_metadata(&self);

    /// Test that loading and updating a `ThreadInfo` acts as expected.
    async fn test_load_and_update_thread_info(&self);

    /// Test that clearing all the rooms' events and linked chunks work.
    async fn test_clear_all_events(&self);

    /// Test that clearing a specific room events and linked chunks works.
    async fn test_clear_all_events_for_specific_room(&self);

    /// Test that filtering duplicated events works as expected.
    async fn test_filter_duplicated_events(&self);

    /// Test that filtering duplicated events works with an empty filter.
    async fn test_filter_duplicate_events_no_events(&self);

    /// Test that an event can be found or not.
    async fn test_find_event(&self);

    /// Test that an event can be found when it exists in both a room and a
    /// thread in that room.
    async fn test_find_event_when_event_in_room_and_thread(&self);

    /// Test that finding event relations works as expected.
    async fn test_find_event_relations(&self);

    /// Test that find event relations works as expected when an event is both a
    /// room and a thread in that room.
    async fn test_find_event_relations_when_event_in_room_and_thread(&self);

    /// Test that getting all events in a room works as expected.
    async fn test_get_room_events(&self);

    /// Test that getting events in a room of a certain type works as expected.
    async fn test_get_room_events_filtered(&self);

    /// Test that getting all events in a room works as expected when the event
    /// is in both a room and thread in that room.
    async fn test_get_room_events_with_event_in_room_and_thread(&self);

    /// Test that saving an event works as expected.
    async fn test_save_event(&self);

    /// Test that saving an existing event updates it's contents in both room
    /// and thread linked chunks.
    async fn test_save_event_updates_event_in_room_and_thread(&self);

    /// Test multiple things related to distinguishing a thread linked chunk
    /// from a room linked chunk.
    async fn test_thread_vs_room_linked_chunk(&self);
}

impl EventCacheStoreIntegrationTests for DynEventCacheStore {
    async fn test_handle_updates_and_rebuild_linked_chunk(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let linked_chunk_id = LinkedChunkId::Room(room_id);

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                // new chunk
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                // new items on 0
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![
                        make_test_event(room_id, "hello"),
                        make_test_event(room_id, "world"),
                    ],
                },
                // a gap chunk
                Update::NewGapChunk {
                    previous: Some(CId::new(0)),
                    new: CId::new(1),
                    next: None,
                    gap: Gap { token: "parmesan".to_owned() },
                },
                // another items chunk
                Update::NewItemsChunk { previous: Some(CId::new(1)), new: CId::new(2), next: None },
                // new items on 2
                Update::PushItems {
                    at: Position::new(CId::new(2), 0),
                    items: vec![make_test_event(room_id, "sup")],
                },
            ],
        )
        .await
        .unwrap();

        // The linked chunk is correctly reloaded.
        let lc = lazy_loader::from_all_chunks::<3, _, _>(
            self.load_all_chunks(linked_chunk_id).await.unwrap(),
        )
        .unwrap()
        .unwrap();

        let mut chunks = lc.chunks();

        {
            let first = chunks.next().unwrap();
            // Note: we can't assert the previous/next chunks, as these fields and their
            // getters are private.
            assert_eq!(first.identifier(), CId::new(0));

            assert_matches!(first.content(), ChunkContent::Items(events) => {
                assert_eq!(events.len(), 2);
                check_test_event(&events[0], "hello");
                check_test_event(&events[1], "world");
            });
        }

        {
            let second = chunks.next().unwrap();
            assert_eq!(second.identifier(), CId::new(1));

            assert_matches!(second.content(), ChunkContent::Gap(gap) => {
                assert_eq!(gap.token, "parmesan");
            });
        }

        {
            let third = chunks.next().unwrap();
            assert_eq!(third.identifier(), CId::new(2));

            assert_matches!(third.content(), ChunkContent::Items(events) => {
                assert_eq!(events.len(), 1);
                check_test_event(&events[0], "sup");
            });
        }

        assert!(chunks.next().is_none());
    }

    async fn test_linked_chunk_exists_before_referenced(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let linked_chunk_id = LinkedChunkId::Room(room_id);

        // Fails to add the chunk because previous chunk is not in the self
        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![Update::NewItemsChunk {
                previous: Some(CId::new(41)),
                new: CId::new(42),
                next: None,
            }],
        )
        .await
        .unwrap_err();

        // Fails to add the chunk because next chunk is not in the self
        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![Update::NewItemsChunk {
                previous: None,
                new: CId::new(42),
                next: Some(CId::new(43)),
            }],
        )
        .await
        .unwrap_err();

        // Fails to add the chunk because previous chunk is not in the self
        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![Update::NewGapChunk {
                previous: Some(CId::new(41)),
                new: CId::new(42),
                next: None,
                gap: Gap { token: "gap".to_owned() },
            }],
        )
        .await
        .unwrap_err();

        // Fails to add the chunk because next chunk is not in the self
        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![Update::NewGapChunk {
                previous: None,
                new: CId::new(42),
                next: Some(CId::new(43)),
                gap: Gap { token: "gap".to_owned() },
            }],
        )
        .await
        .unwrap_err();
    }

    async fn test_linked_chunk_allows_same_event_in_room_and_thread(&self) {
        // This test verifies that the same event can appear in both a room's linked
        // chunk and a thread's linked chunk. This is the real-world use case:
        // a thread reply appears in both the main room timeline and the thread.

        let room_id = *DEFAULT_TEST_ROOM_ID;
        let thread_root = event_id!("$thread_root");

        // Create an event that will be inserted into both the room and thread linked
        // chunks.
        let event_id = event_id!("$thread_reply");
        let event = make_test_event_with_event_id(room_id, "thread reply", Some(event_id));

        let room_linked_chunk_id = LinkedChunkId::Room(room_id);
        let thread_linked_chunk_id = LinkedChunkId::Thread(room_id, thread_root);

        // Insert the event into the room's linked chunk.
        self.handle_linked_chunk_updates(
            room_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems { at: Position::new(CId::new(1), 0), items: vec![event.clone()] },
            ],
        )
        .await
        .unwrap();

        // Insert the same event into the thread's linked chunk.
        self.handle_linked_chunk_updates(
            thread_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems { at: Position::new(CId::new(1), 0), items: vec![event] },
            ],
        )
        .await
        .unwrap();

        // Verify both entries exist by loading chunks from both linked chunk IDs.
        let room_chunks = self.load_all_chunks(room_linked_chunk_id).await.unwrap();
        let thread_chunks = self.load_all_chunks(thread_linked_chunk_id).await.unwrap();

        assert_eq!(room_chunks.len(), 1);
        assert_eq!(thread_chunks.len(), 1);

        // Verify the event is in both.
        assert_matches!(&room_chunks[0].content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 1);
            assert_eq!(events[0].event_id(), Some(event_id));
        });
        assert_matches!(&thread_chunks[0].content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 1);
            assert_eq!(events[0].event_id(), Some(event_id));
        });
    }

    async fn test_load_all_chunks_metadata(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let linked_chunk_id = LinkedChunkId::Room(room_id);

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                // new chunk
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                // new items on 0
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![
                        make_test_event(room_id, "hello"),
                        make_test_event(room_id, "world"),
                    ],
                },
                // a gap chunk
                Update::NewGapChunk {
                    previous: Some(CId::new(0)),
                    new: CId::new(1),
                    next: None,
                    gap: Gap { token: "parmesan".to_owned() },
                },
                // another items chunk
                Update::NewItemsChunk { previous: Some(CId::new(1)), new: CId::new(2), next: None },
                // new items on 2
                Update::PushItems {
                    at: Position::new(CId::new(2), 0),
                    items: vec![make_test_event(room_id, "sup")],
                },
                // and an empty items chunk to finish
                Update::NewItemsChunk { previous: Some(CId::new(2)), new: CId::new(3), next: None },
            ],
        )
        .await
        .unwrap();

        let metas = self.load_all_chunks_metadata(linked_chunk_id).await.unwrap();
        assert_eq!(metas.len(), 4);

        // The first chunk has two items.
        assert_eq!(metas[0].identifier, CId::new(0));
        assert_eq!(metas[0].previous, None);
        assert_eq!(metas[0].next, Some(CId::new(1)));
        assert_eq!(metas[0].num_items, 2);

        // The second chunk is a gap, so it has 0 items.
        assert_eq!(metas[1].identifier, CId::new(1));
        assert_eq!(metas[1].previous, Some(CId::new(0)));
        assert_eq!(metas[1].next, Some(CId::new(2)));
        assert_eq!(metas[1].num_items, 0);

        // The third event chunk has one item.
        assert_eq!(metas[2].identifier, CId::new(2));
        assert_eq!(metas[2].previous, Some(CId::new(1)));
        assert_eq!(metas[2].next, Some(CId::new(3)));
        assert_eq!(metas[2].num_items, 1);

        // The final event chunk is empty.
        assert_eq!(metas[3].identifier, CId::new(3));
        assert_eq!(metas[3].previous, Some(CId::new(2)));
        assert_eq!(metas[3].next, None);
        assert_eq!(metas[3].num_items, 0);
    }

    async fn test_load_last_chunk(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let linked_chunk_id = LinkedChunkId::Room(room_id);
        let event = |msg: &str| make_test_event(room_id, msg);

        // Case #1: no last chunk.
        {
            let (last_chunk, chunk_identifier_generator) =
                self.load_last_chunk(linked_chunk_id).await.unwrap();

            assert!(last_chunk.is_none());
            assert_eq!(chunk_identifier_generator.current(), 0);
        }

        // Case #2: only one chunk is present.
        {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![
                    Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                    Update::PushItems {
                        at: Position::new(CId::new(42), 0),
                        items: vec![event("saucisse de morteau"), event("comté")],
                    },
                ],
            )
            .await
            .unwrap();

            let (last_chunk, chunk_identifier_generator) =
                self.load_last_chunk(linked_chunk_id).await.unwrap();

            assert_matches!(last_chunk, Some(last_chunk) => {
                assert_eq!(last_chunk.identifier, 42);
                assert!(last_chunk.previous.is_none());
                assert!(last_chunk.next.is_none());
                assert_matches!(last_chunk.content, ChunkContent::Items(items) => {
                    assert_eq!(items.len(), 2);
                    check_test_event(&items[0], "saucisse de morteau");
                    check_test_event(&items[1], "comté");
                });
            });
            assert_eq!(chunk_identifier_generator.current(), 42);
        }

        // Case #3: more chunks are present.
        {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![
                    Update::NewItemsChunk {
                        previous: Some(CId::new(42)),
                        new: CId::new(7),
                        next: None,
                    },
                    Update::PushItems {
                        at: Position::new(CId::new(7), 0),
                        items: vec![event("fondue"), event("gruyère"), event("mont d'or")],
                    },
                ],
            )
            .await
            .unwrap();

            let (last_chunk, chunk_identifier_generator) =
                self.load_last_chunk(linked_chunk_id).await.unwrap();

            assert_matches!(last_chunk, Some(last_chunk) => {
                assert_eq!(last_chunk.identifier, 7);
                assert_matches!(last_chunk.previous, Some(previous) => {
                    assert_eq!(previous, 42);
                });
                assert!(last_chunk.next.is_none());
                assert_matches!(last_chunk.content, ChunkContent::Items(items) => {
                    assert_eq!(items.len(), 3);
                    check_test_event(&items[0], "fondue");
                    check_test_event(&items[1], "gruyère");
                    check_test_event(&items[2], "mont d'or");
                });
            });
            assert_eq!(chunk_identifier_generator.current(), 42);
        }
    }

    async fn test_load_last_chunk_with_a_cycle(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let linked_chunk_id = LinkedChunkId::Room(room_id);

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::NewItemsChunk {
                    // Because `previous` connects to chunk #0, it will create a cycle.
                    // Chunk #0 will have a `next` set to chunk #1! Consequently, the last chunk
                    // **does not exist**. We have to detect this cycle.
                    previous: Some(CId::new(0)),
                    new: CId::new(1),
                    next: Some(CId::new(0)),
                },
            ],
        )
        .await
        .unwrap();

        self.load_last_chunk(linked_chunk_id).await.unwrap_err();
    }

    async fn test_load_previous_chunk(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let linked_chunk_id = LinkedChunkId::Room(room_id);
        let event = |msg: &str| make_test_event(room_id, msg);

        // Case #1: no chunk at all, equivalent to having an nonexistent
        // `before_chunk_identifier`.
        {
            let previous_chunk =
                self.load_previous_chunk(linked_chunk_id, CId::new(153)).await.unwrap();

            assert!(previous_chunk.is_none());
        }

        // Case #2: there is one chunk only: we request the previous on this
        // one, it doesn't exist.
        {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![Update::NewItemsChunk { previous: None, new: CId::new(42), next: None }],
            )
            .await
            .unwrap();

            let previous_chunk =
                self.load_previous_chunk(linked_chunk_id, CId::new(42)).await.unwrap();

            assert!(previous_chunk.is_none());
        }

        // Case #3: there are two chunks.
        {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![
                    // new chunk before the one that exists.
                    Update::NewItemsChunk {
                        previous: None,
                        new: CId::new(7),
                        next: Some(CId::new(42)),
                    },
                    Update::PushItems {
                        at: Position::new(CId::new(7), 0),
                        items: vec![event("brigand du jorat"), event("morbier")],
                    },
                ],
            )
            .await
            .unwrap();

            let previous_chunk =
                self.load_previous_chunk(linked_chunk_id, CId::new(42)).await.unwrap();

            assert_matches!(previous_chunk, Some(previous_chunk) => {
                assert_eq!(previous_chunk.identifier, 7);
                assert!(previous_chunk.previous.is_none());
                assert_matches!(previous_chunk.next, Some(next) => {
                    assert_eq!(next, 42);
                });
                assert_matches!(previous_chunk.content, ChunkContent::Items(items) => {
                    assert_eq!(items.len(), 2);
                    check_test_event(&items[0], "brigand du jorat");
                    check_test_event(&items[1], "morbier");
                });
            });
        }
    }

    async fn test_linked_chunk_incremental_loading(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let linked_chunk_id = LinkedChunkId::Room(room_id);
        let event = |msg: &str| make_test_event(room_id, msg);

        // Load the last chunk, but none exists yet.
        {
            let (last_chunk, chunk_identifier_generator) =
                self.load_last_chunk(linked_chunk_id).await.unwrap();

            assert!(last_chunk.is_none());
            assert_eq!(chunk_identifier_generator.current(), 0);
        }

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                // new chunk for items
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                // new items on 0
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![event("a"), event("b")],
                },
                // new chunk for a gap
                Update::NewGapChunk {
                    previous: Some(CId::new(0)),
                    new: CId::new(1),
                    next: None,
                    gap: Gap { token: "morbier".to_owned() },
                },
                // new chunk for items
                Update::NewItemsChunk { previous: Some(CId::new(1)), new: CId::new(2), next: None },
                // new items on 2
                Update::PushItems {
                    at: Position::new(CId::new(2), 0),
                    items: vec![event("c"), event("d"), event("e")],
                },
            ],
        )
        .await
        .unwrap();

        // Load the last chunk.
        let mut linked_chunk = {
            let (last_chunk, chunk_identifier_generator) =
                self.load_last_chunk(linked_chunk_id).await.unwrap();

            assert_eq!(chunk_identifier_generator.current(), 2);

            let linked_chunk = lazy_loader::from_last_chunk::<DEFAULT_CHUNK_CAPACITY, _, _>(
                last_chunk,
                chunk_identifier_generator,
            )
            .unwrap() // unwrap the `Result`
            .unwrap(); // unwrap the `Option`

            let mut rchunks = linked_chunk.rchunks();

            // A unique chunk.
            assert_matches!(rchunks.next(), Some(chunk) => {
                assert_eq!(chunk.identifier(), 2);
                assert_eq!(chunk.lazy_previous(), Some(CId::new(1)));

                assert_matches!(chunk.content(), ChunkContent::Items(events) => {
                    assert_eq!(events.len(), 3);
                    check_test_event(&events[0], "c");
                    check_test_event(&events[1], "d");
                    check_test_event(&events[2], "e");
                });
            });

            assert!(rchunks.next().is_none());

            linked_chunk
        };

        // Load the previous chunk: this is a gap.
        {
            let first_chunk = linked_chunk.chunks().next().unwrap().identifier();
            let previous_chunk =
                self.load_previous_chunk(linked_chunk_id, first_chunk).await.unwrap().unwrap();

            lazy_loader::insert_new_first_chunk(&mut linked_chunk, previous_chunk).unwrap();

            let mut rchunks = linked_chunk.rchunks();

            // The last chunk.
            assert_matches!(rchunks.next(), Some(chunk) => {
                assert_eq!(chunk.identifier(), 2);
                assert!(chunk.lazy_previous().is_none());

                // Already asserted, but let's be sure nothing breaks.
                assert_matches!(chunk.content(), ChunkContent::Items(events) => {
                    assert_eq!(events.len(), 3);
                    check_test_event(&events[0], "c");
                    check_test_event(&events[1], "d");
                    check_test_event(&events[2], "e");
                });
            });

            // The new chunk.
            assert_matches!(rchunks.next(), Some(chunk) => {
                assert_eq!(chunk.identifier(), 1);
                assert_eq!(chunk.lazy_previous(), Some(CId::new(0)));

                assert_matches!(chunk.content(), ChunkContent::Gap(gap) => {
                    assert_eq!(gap.token, "morbier");
                });
            });

            assert!(rchunks.next().is_none());
        }

        // Load the previous chunk: these are items.
        {
            let first_chunk = linked_chunk.chunks().next().unwrap().identifier();
            let previous_chunk =
                self.load_previous_chunk(linked_chunk_id, first_chunk).await.unwrap().unwrap();

            lazy_loader::insert_new_first_chunk(&mut linked_chunk, previous_chunk).unwrap();

            let mut rchunks = linked_chunk.rchunks();

            // The last chunk.
            assert_matches!(rchunks.next(), Some(chunk) => {
                assert_eq!(chunk.identifier(), 2);
                assert!(chunk.lazy_previous().is_none());

                // Already asserted, but let's be sure nothing breaks.
                assert_matches!(chunk.content(), ChunkContent::Items(events) => {
                    assert_eq!(events.len(), 3);
                    check_test_event(&events[0], "c");
                    check_test_event(&events[1], "d");
                    check_test_event(&events[2], "e");
                });
            });

            // Its previous chunk.
            assert_matches!(rchunks.next(), Some(chunk) => {
                assert_eq!(chunk.identifier(), 1);
                assert!(chunk.lazy_previous().is_none());

                // Already asserted, but let's be sure nothing breaks.
                assert_matches!(chunk.content(), ChunkContent::Gap(gap) => {
                    assert_eq!(gap.token, "morbier");
                });
            });

            // The new chunk.
            assert_matches!(rchunks.next(), Some(chunk) => {
                assert_eq!(chunk.identifier(), 0);
                assert!(chunk.lazy_previous().is_none());

                assert_matches!(chunk.content(), ChunkContent::Items(events) => {
                    assert_eq!(events.len(), 2);
                    check_test_event(&events[0], "a");
                    check_test_event(&events[1], "b");
                });
            });

            assert!(rchunks.next().is_none());
        }

        // Load the previous chunk: there is none.
        {
            let first_chunk = linked_chunk.chunks().next().unwrap().identifier();
            let previous_chunk =
                self.load_previous_chunk(linked_chunk_id, first_chunk).await.unwrap();

            assert!(previous_chunk.is_none());
        }

        // One last check: a round of assert by using the forwards chunk iterator
        // instead of the backwards chunk iterator.
        {
            let mut chunks = linked_chunk.chunks();

            // The first chunk.
            assert_matches!(chunks.next(), Some(chunk) => {
                assert_eq!(chunk.identifier(), 0);
                assert!(chunk.lazy_previous().is_none());

                assert_matches!(chunk.content(), ChunkContent::Items(events) => {
                    assert_eq!(events.len(), 2);
                    check_test_event(&events[0], "a");
                    check_test_event(&events[1], "b");
                });
            });

            // The second chunk.
            assert_matches!(chunks.next(), Some(chunk) => {
                assert_eq!(chunk.identifier(), 1);
                assert!(chunk.lazy_previous().is_none());

                assert_matches!(chunk.content(), ChunkContent::Gap(gap) => {
                    assert_eq!(gap.token, "morbier");
                });
            });

            // The third and last chunk.
            assert_matches!(chunks.next(), Some(chunk) => {
                assert_eq!(chunk.identifier(), 2);
                assert!(chunk.lazy_previous().is_none());

                assert_matches!(chunk.content(), ChunkContent::Items(events) => {
                    assert_eq!(events.len(), 3);
                    check_test_event(&events[0], "c");
                    check_test_event(&events[1], "d");
                    check_test_event(&events[2], "e");
                });
            });

            assert!(chunks.next().is_none());
        }
    }

    async fn test_linked_chunk_remove_chunk(&self) {
        let room_id = &DEFAULT_TEST_ROOM_ID;
        let linked_chunk_id = LinkedChunkId::Room(room_id);

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewGapChunk {
                    previous: None,
                    new: CId::new(42),
                    next: None,
                    gap: Gap { token: "raclette".to_owned() },
                },
                Update::NewGapChunk {
                    previous: Some(CId::new(42)),
                    new: CId::new(43),
                    next: None,
                    gap: Gap { token: "fondue".to_owned() },
                },
                Update::NewGapChunk {
                    previous: Some(CId::new(43)),
                    new: CId::new(44),
                    next: None,
                    gap: Gap { token: "tartiflette".to_owned() },
                },
                Update::RemoveChunk(CId::new(43)),
            ],
        )
        .await
        .unwrap();

        let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();

        assert_eq!(chunks.len(), 2);

        // Chunks are ordered from smaller to bigger IDs.
        let c = chunks.remove(0);
        assert_eq!(c.identifier, CId::new(42));
        assert_eq!(c.previous, None);
        assert_eq!(c.next, Some(CId::new(44)));
        assert_matches!(c.content, ChunkContent::Gap(gap) => {
            assert_eq!(gap.token, "raclette");
        });

        let c = chunks.remove(0);
        assert_eq!(c.identifier, CId::new(44));
        assert_eq!(c.previous, Some(CId::new(42)));
        assert_eq!(c.next, None);
        assert_matches!(c.content, ChunkContent::Gap(gap) => {
            assert_eq!(gap.token, "tartiflette");
        });
    }

    async fn test_linked_chunk_push_items(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;

        // Create every kind of linked chunk id in the room.
        let linked_chunk_ids = [
            LinkedChunkId::Room(room_id),
            LinkedChunkId::Thread(room_id, event_id!("$thread_root")),
            LinkedChunkId::PinnedEvents(room_id),
            LinkedChunkId::EventFocused(room_id, event_id!("$focus_root")),
        ];

        // Add the same event to every linked chunk
        let event_id_a = event_id!("$a");
        let event_a = make_test_event_with_event_id(room_id, "a", Some(event_id_a));
        for linked_chunk_id in linked_chunk_ids {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![
                    Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                    Update::PushItems {
                        at: Position::new(CId::new(0), 0),
                        items: vec![event_a.clone()],
                    },
                ],
            )
            .await
            .unwrap();

            let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();
            assert_eq!(chunks.len(), 1);
            let chunk = chunks.remove(0);
            assert_matches!(chunk.content, ChunkContent::Items(events) => {
                assert_eq!(events.len(), 1);
                check_test_event(&events[0], "a");
            });
        }

        let event_b = make_test_event_with_event_id(room_id, "b", Some(event_id!("$b")));
        // Pushing an event to an occupied position should fail in every linked chunk.
        for linked_chunk_id in linked_chunk_ids {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![event_b.clone()],
                }],
            )
            .await
            .expect_err("should fail to push an event to an occupied position");

            let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();
            assert_eq!(chunks.len(), 1);
            let chunk = chunks.remove(0);
            assert_matches!(chunk.content, ChunkContent::Items(events) => {
                assert_eq!(events.len(), 1);
                check_test_event(&events[0], "a");
            });
        }

        // Pushing an event to an unoccupied position should succeed in every linked
        // chunk.
        for linked_chunk_id in linked_chunk_ids {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![Update::PushItems {
                    at: Position::new(CId::new(0), 1),
                    items: vec![event_b.clone()],
                }],
            )
            .await
            .unwrap();

            let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();
            assert_eq!(chunks.len(), 1);
            let chunk = chunks.remove(0);
            assert_matches!(chunk.content, ChunkContent::Items(events) => {
                assert_eq!(events.len(), 2);
                check_test_event(&events[0], "a");
                check_test_event(&events[1], "b");
            });
        }

        // Create an updated version of event a
        let updated_event_a = make_test_event_with_event_id(room_id, "updated_a", Some(event_id_a));

        // Pushing an updated event to a position occupied by the same event should
        // fail in every linked chunk.
        for linked_chunk_id in linked_chunk_ids {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![updated_event_a.clone()],
                }],
            )
            .await
            .expect_err("should fail to push an event to an occupied position");

            let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();
            assert_eq!(chunks.len(), 1);
            let chunk = chunks.remove(0);
            assert_matches!(chunk.content, ChunkContent::Items(events) => {
                assert_eq!(events.len(), 2);
                check_test_event(&events[0], "a");
                check_test_event(&events[1], "b");
            });
        }

        // Pushing an updated event to a position occupied by a different event should
        // fail in every linked chunk.
        for linked_chunk_id in linked_chunk_ids {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![Update::PushItems {
                    at: Position::new(CId::new(0), 1),
                    items: vec![updated_event_a.clone()],
                }],
            )
            .await
            .expect_err("should fail to push an event to an occupied position");

            let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();
            assert_eq!(chunks.len(), 1);
            let chunk = chunks.remove(0);
            assert_matches!(chunk.content, ChunkContent::Items(events) => {
                assert_eq!(events.len(), 2);
                check_test_event(&events[0], "a");
                check_test_event(&events[1], "b");
            });
        }

        // Pushing an updated event to an unoccupied position in a linked chunk should
        // fail if the event already exists in the linked chunk.
        for linked_chunk_id in linked_chunk_ids {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![Update::PushItems {
                    at: Position::new(CId::new(0), 2),
                    items: vec![updated_event_a.clone()],
                }],
            )
            .await
            .expect_err("should fail to push an event that already exists in the linked chunk");

            let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();
            assert_eq!(chunks.len(), 1);
            let chunk = chunks.remove(0);
            assert_matches!(chunk.content, ChunkContent::Items(events) => {
                assert_eq!(events.len(), 2);
                check_test_event(&events[0], "a");
                check_test_event(&events[1], "b");
            });
        }

        // Create a new linked chunk in a new room that does not contain event a
        let other_linked_chunk_id = LinkedChunkId::Room(room_id!("!other_room:localhost"));
        self.handle_linked_chunk_updates(
            other_linked_chunk_id,
            vec![Update::NewItemsChunk { previous: None, new: CId::new(0), next: None }],
        )
        .await
        .unwrap();

        // Pushing an updated version of event a to an unoccupied position in the new
        // linked chunk should succeed and also update the event content across all
        // linked chunks in all rooms.
        self.handle_linked_chunk_updates(
            other_linked_chunk_id,
            vec![Update::PushItems {
                at: Position::new(CId::new(0), 0),
                items: vec![updated_event_a.clone()],
            }],
        )
        .await
        .unwrap();

        let mut chunks = self.load_all_chunks(other_linked_chunk_id).await.unwrap();
        assert_eq!(chunks.len(), 1);
        let chunk = chunks.remove(0);
        assert_matches!(chunk.content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 1);
            check_test_event(&events[0], "updated_a");
        });

        for linked_chunk_id in linked_chunk_ids {
            let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();
            assert_eq!(chunks.len(), 1);
            let chunk = chunks.remove(0);
            assert_matches!(chunk.content, ChunkContent::Items(events) => {
                assert_eq!(events.len(), 2);
                check_test_event(&events[0], "updated_a");
                check_test_event(&events[1], "b");
            });
        }
    }

    async fn test_linked_chunk_replace_item(&self) {
        let room_id = &DEFAULT_TEST_ROOM_ID;

        // Create every kind of linked chunk id in the room, as well
        // as one in a different room.
        let linked_chunk_ids = [
            LinkedChunkId::Room(room_id),
            LinkedChunkId::Thread(room_id, event_id!("$thread_root")),
            LinkedChunkId::PinnedEvents(room_id),
            LinkedChunkId::EventFocused(room_id, event_id!("$focus_root")),
            LinkedChunkId::Room(room_id!("!other_room")),
        ];

        // The event id of the event that will be replaced
        let event_id = event_id!("$world");

        // Add the same two events to every linked chunk id in the list
        for linked_chunk_id in linked_chunk_ids {
            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![
                    Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                    Update::PushItems {
                        at: Position::new(CId::new(42), 0),
                        items: vec![
                            make_test_event(room_id, "hello"),
                            make_test_event_with_event_id(room_id, "world", Some(event_id)),
                        ],
                    },
                ],
            )
            .await
            .unwrap();

            let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();

            assert_eq!(chunks.len(), 1);

            let c = chunks.remove(0);
            assert_eq!(c.identifier, CId::new(42));
            assert_eq!(c.previous, None);
            assert_eq!(c.next, None);
            assert_matches!(c.content, ChunkContent::Items(events) => {
                assert_eq!(events.len(), 2);
                check_test_event(&events[0], "hello");
                check_test_event(&events[1], "world");
            });
        }

        // In one of the linked chunks, replace the second event with different
        // content, but keep the event id the same.
        self.handle_linked_chunk_updates(
            linked_chunk_ids[0],
            vec![Update::ReplaceItem {
                at: Position::new(CId::new(42), 1),
                item: make_test_event_with_event_id(room_id, "yolo", Some(event_id)),
            }],
        )
        .await
        .unwrap();

        // Ensure that the event content has been updated in every linked chunk.
        for linked_chunk_id in linked_chunk_ids {
            let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();

            assert_eq!(chunks.len(), 1);

            let c = chunks.remove(0);
            assert_eq!(c.identifier, CId::new(42));
            assert_eq!(c.previous, None);
            assert_eq!(c.next, None);
            assert_matches!(c.content, ChunkContent::Items(events) => {
                assert_eq!(events.len(), 2);
                check_test_event(&events[0], "hello");
                check_test_event(&events[1], "yolo");
            });
        }
    }

    async fn test_linked_chunk_remove_item(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let linked_chunk_id = LinkedChunkId::Room(room_id);

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(42), 0),
                    items: vec![
                        make_test_event(room_id, "one"),
                        make_test_event(room_id, "two"),
                        make_test_event(room_id, "three"),
                        make_test_event(room_id, "four"),
                        make_test_event(room_id, "five"),
                        make_test_event(room_id, "six"),
                    ],
                },
                Update::RemoveItem { at: Position::new(CId::new(42), 2) /* "three" */ },
                // After removing an item, we need to ensure that the indices of all subsequent
                // items in the chunk have shifted down by one. We can ensure this by pushing
                // an item at the smallest index we expect to be unoccupied, and checking to see
                // whether the last item in the chunk was overwritten.
                //
                // For example, after removing the item at index 2, we should have 5 elements and
                // the smallest unoccupied index should be index 5. If we push an item to index 5,
                // it should not overwrite any existing elements - i.e., "six" - but should be
                // appended to the end of the chunk.
                Update::PushItems {
                    at: Position::new(CId::new(42), 5),
                    items: vec![make_test_event(room_id, "seven")],
                },
            ],
        )
        .await
        .unwrap();

        let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();

        assert_eq!(chunks.len(), 1);

        let c = chunks.remove(0);
        assert_eq!(c.identifier, CId::new(42));
        assert_eq!(c.previous, None);
        assert_eq!(c.next, None);
        assert_matches!(c.content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 6);
            check_test_event(&events[0], "one");
            check_test_event(&events[1], "two");
            check_test_event(&events[2], "four");
            check_test_event(&events[3], "five");
            check_test_event(&events[4], "six");
            check_test_event(&events[5], "seven");
        });

        // The chunk metadata must agree on the number of items.
        let metas = self.load_all_chunks_metadata(linked_chunk_id).await.unwrap();
        assert_eq!(metas.len(), 1);
        assert_eq!(metas[0].num_items, 6);
    }

    async fn test_linked_chunk_detach_last_items(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let linked_chunk_id = LinkedChunkId::Room(room_id);

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(42), 0),
                    items: vec![
                        make_test_event(room_id, "hello"),
                        make_test_event(room_id, "world"),
                        make_test_event(room_id, "howdy"),
                    ],
                },
                Update::DetachLastItems { at: Position::new(CId::new(42), 1) },
            ],
        )
        .await
        .unwrap();

        let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();

        assert_eq!(chunks.len(), 1);

        let c = chunks.remove(0);
        assert_eq!(c.identifier, CId::new(42));
        assert_eq!(c.previous, None);
        assert_eq!(c.next, None);
        assert_matches!(c.content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 1);
            check_test_event(&events[0], "hello");
        });
    }

    async fn test_linked_chunk_start_end_reattach_items(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let linked_chunk_id = LinkedChunkId::Room(room_id);

        // Same updates and checks as test_linked_chunk_push_items, but with extra
        // `StartReattachItems` and `EndReattachItems` updates, which must have no
        // effects.
        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(42), 0),
                    items: vec![
                        make_test_event(room_id, "hello"),
                        make_test_event(room_id, "world"),
                        make_test_event(room_id, "howdy"),
                    ],
                },
                Update::StartReattachItems,
                Update::EndReattachItems,
            ],
        )
        .await
        .unwrap();

        let mut chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();

        assert_eq!(chunks.len(), 1);

        let c = chunks.remove(0);
        assert_eq!(c.identifier, CId::new(42));
        assert_eq!(c.previous, None);
        assert_eq!(c.next, None);
        assert_matches!(c.content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 3);
            check_test_event(&events[0], "hello");
            check_test_event(&events[1], "world");
            check_test_event(&events[2], "howdy");
        });
    }

    async fn test_linked_chunk_clear(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let linked_chunk_id = LinkedChunkId::Room(room_id);
        let event_0 = make_test_event(room_id, "hello");
        let event_1 = make_test_event(room_id, "world");
        let event_2 = make_test_event(room_id, "howdy");

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                Update::NewGapChunk {
                    previous: Some(CId::new(42)),
                    new: CId::new(54),
                    next: None,
                    gap: Gap { token: "fondue".to_owned() },
                },
                Update::PushItems {
                    at: Position::new(CId::new(42), 0),
                    items: vec![event_0.clone(), event_1, event_2],
                },
                Update::Clear,
            ],
        )
        .await
        .unwrap();

        let chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();
        assert!(chunks.is_empty());
    }

    async fn test_linked_chunk_clear_and_reinsert(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let linked_chunk_id = LinkedChunkId::Room(room_id);
        let event_0 = make_test_event(room_id, "hello");
        let event_1 = make_test_event(room_id, "world");
        let event_2 = make_test_event(room_id, "howdy");

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                Update::NewGapChunk {
                    previous: Some(CId::new(42)),
                    new: CId::new(54),
                    next: None,
                    gap: Gap { token: "fondue".to_owned() },
                },
                Update::PushItems {
                    at: Position::new(CId::new(42), 0),
                    items: vec![event_0.clone(), event_1, event_2],
                },
                Update::Clear,
            ],
        )
        .await
        .unwrap();

        let chunks = self.load_all_chunks(linked_chunk_id).await.unwrap();
        assert!(chunks.is_empty());

        // It's okay to re-insert a past event.
        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                Update::PushItems { at: Position::new(CId::new(42), 0), items: vec![event_0] },
            ],
        )
        .await
        .unwrap();
    }

    async fn test_rebuild_empty_linked_chunk(&self) {
        // When I rebuild a linked chunk from an empty store, it's empty.
        let linked_chunk = lazy_loader::from_all_chunks::<3, _, _>(
            self.load_all_chunks(LinkedChunkId::Room(&DEFAULT_TEST_ROOM_ID)).await.unwrap(),
        )
        .unwrap();
        assert!(linked_chunk.is_none());
    }

    async fn test_linked_chunk_multiple_rooms(&self) {
        let room1 = room_id!("!realcheeselovers:raclette.fr");
        let linked_chunk_id1 = LinkedChunkId::Room(room1);
        let room2 = room_id!("!realcheeselovers:fondue.ch");
        let linked_chunk_id2 = LinkedChunkId::Room(room2);

        // Check that applying updates to one room doesn't affect the others.
        // Use the same chunk identifier in both rooms to battle-test search.

        self.handle_linked_chunk_updates(
            linked_chunk_id1,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(42), 0),
                    items: vec![
                        make_test_event(room1, "best cheese is raclette"),
                        make_test_event(room1, "obviously"),
                    ],
                },
            ],
        )
        .await
        .unwrap();

        self.handle_linked_chunk_updates(
            linked_chunk_id2,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(42), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(42), 0),
                    items: vec![make_test_event(room1, "beaufort is the best")],
                },
            ],
        )
        .await
        .unwrap();

        // Check chunks from room 1.
        let mut chunks_room1 = self.load_all_chunks(linked_chunk_id1).await.unwrap();
        assert_eq!(chunks_room1.len(), 1);

        let c = chunks_room1.remove(0);
        assert_matches!(c.content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 2);
            check_test_event(&events[0], "best cheese is raclette");
            check_test_event(&events[1], "obviously");
        });

        // Check chunks from room 2.
        let mut chunks_room2 = self.load_all_chunks(linked_chunk_id2).await.unwrap();
        assert_eq!(chunks_room2.len(), 1);

        let c = chunks_room2.remove(0);
        assert_matches!(c.content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 1);
            check_test_event(&events[0], "beaufort is the best");
        });
    }

    async fn test_load_and_update_thread_info(&self) {
        let room_id = room_id!("!r0");
        let thread_id = event_id!("$t0");

        // Load for the first time.
        //
        // We must get an empty `ThreadInfo`.
        let ThreadInfo { read_receipts } = self.load_thread_info(room_id, thread_id).await.unwrap();
        let ReadReceipts { num_unread, num_notifications, num_mentions, latest_active, pending } =
            read_receipts;
        assert_eq!(num_unread, 0);
        assert_eq!(num_notifications, 0);
        assert_eq!(num_mentions, 0);
        assert!(latest_active.is_none());
        assert!(pending.is_empty());

        // Load for the second time.
        //
        // We must get the same empty `ThreadInfo`.
        let mut thread_info = self.load_thread_info(room_id, thread_id).await.unwrap();
        let ThreadInfo { read_receipts } = &thread_info;
        let ReadReceipts { num_unread, num_notifications, num_mentions, latest_active, pending } =
            read_receipts;
        assert_eq!(*num_unread, 0);
        assert_eq!(*num_notifications, 0);
        assert_eq!(*num_mentions, 0);
        assert!(latest_active.is_none());
        assert!(pending.is_empty());

        // Update the `ThreadInfo`.
        thread_info.read_receipts.num_unread = 1;
        thread_info.read_receipts.num_notifications = 2;
        self.update_thread_info(room_id, thread_id, &thread_info).await.unwrap();

        // Load for the third time.
        //
        // We must get the updated `ThreadInfo`.
        let ThreadInfo { read_receipts } = self.load_thread_info(room_id, thread_id).await.unwrap();
        let ReadReceipts { num_unread, num_notifications, num_mentions, latest_active, pending } =
            read_receipts;
        assert_eq!(num_unread, 1);
        assert_eq!(num_notifications, 2);
        assert_eq!(num_mentions, 0);
        assert!(latest_active.is_none());
        assert!(pending.is_empty());
    }

    async fn test_clear_all_events(&self) {
        let linked_chunk_ids = [
            LinkedChunkId::Room(room_id!("!r0")),
            LinkedChunkId::Thread(room_id!("!r1"), event_id!("$r1_thread_root0")),
            LinkedChunkId::PinnedEvents(room_id!("!r2")),
            // `LinkedChunkId::EventFocused` are not persisted in the database, no need to test it.
        ];

        // Create data for each `LinkedChunkId`.
        for linked_chunk_id in linked_chunk_ids {
            let room_id = linked_chunk_id.room_id();

            // Assume the thread has been “remembered” correctly (this is done in
            // `ThreadEventCacheState::new`).
            if let LinkedChunkId::Thread(_, thread_id) = &linked_chunk_id {
                self.load_thread_info(room_id, thread_id).await.unwrap();
            }

            self.handle_linked_chunk_updates(
                linked_chunk_id,
                vec![
                    // New chunk
                    Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                    // New items on 0.
                    Update::PushItems {
                        at: Position::new(CId::new(0), 0),
                        items: vec![
                            make_test_event(room_id, "foo"),
                            make_test_event(room_id, "bar"),
                            make_test_event(room_id, "baz"),
                        ],
                    },
                ],
            )
            .await
            .unwrap();

            // Linked chunks all exist!
            assert!(
                lazy_loader::from_all_chunks::<3, _, _>(
                    self.load_all_chunks(linked_chunk_id).await.unwrap()
                )
                .unwrap()
                .is_some()
            );

            // Events exist!
            assert_eq!(self.get_room_events(room_id, None, None).await.unwrap().len(), 3);
        }

        // Clear all events!
        self.clear_all_events(None).await.unwrap();

        // Check all data have been removed, forever.
        for linked_chunk_id in linked_chunk_ids {
            let room_id = linked_chunk_id.room_id();

            // No more linked chunks!
            assert!(
                lazy_loader::from_all_chunks::<3, _, _>(
                    self.load_all_chunks(linked_chunk_id).await.unwrap()
                )
                .unwrap()
                .is_none()
            );

            // No more events!
            assert!(self.get_room_events(room_id, None, None).await.unwrap().is_empty());
        }
    }

    async fn test_clear_all_events_for_specific_room(&self) {
        let linked_chunk_ids_for_room_0 = [
            LinkedChunkId::Room(room_id!("!r0")),
            LinkedChunkId::Thread(room_id!("!r0"), event_id!("$r0_thread_root")),
            LinkedChunkId::PinnedEvents(room_id!("!r0")),
        ];
        let linked_chunk_ids_for_room_1 = [
            LinkedChunkId::Room(room_id!("!r1")),
            LinkedChunkId::Thread(room_id!("!r1"), event_id!("$r1_thread_root")),
            LinkedChunkId::PinnedEvents(room_id!("!r1")),
        ];
        let linked_chunk_ids_for_room_2 = [
            LinkedChunkId::Room(room_id!("!r2")),
            LinkedChunkId::Thread(room_id!("!r2"), event_id!("$r2_thread_root")),
            LinkedChunkId::PinnedEvents(room_id!("!r2")),
        ];

        // Create data for each `LinkedChunkId`.
        for linked_chunk_id in linked_chunk_ids_for_room_0
            .iter()
            .chain(&linked_chunk_ids_for_room_1)
            .chain(&linked_chunk_ids_for_room_2)
        {
            let room_id = linked_chunk_id.room_id();

            // Assume the thread has been “remembered” correctly (this is done in
            // `ThreadEventCacheState::new`).
            if let LinkedChunkId::Thread(_, thread_id) = &linked_chunk_id {
                self.load_thread_info(room_id, thread_id).await.unwrap();
            }

            self.handle_linked_chunk_updates(
                *linked_chunk_id,
                vec![
                    // New chunk
                    Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                    // New items on 0.
                    Update::PushItems {
                        at: Position::new(CId::new(0), 0),
                        items: vec![
                            make_test_event(room_id, "foo"),
                            make_test_event(room_id, "bar"),
                            make_test_event(room_id, "baz"),
                        ],
                    },
                ],
            )
            .await
            .unwrap();

            // Linked chunks all exist!
            assert!(
                lazy_loader::from_all_chunks::<3, _, _>(
                    self.load_all_chunks(*linked_chunk_id).await.unwrap()
                )
                .unwrap()
                .is_some()
            );

            // Events exist!
            assert_eq!(self.get_room_events(room_id, None, None).await.unwrap().len(), 3);
        }

        // Clear all events for room 1 **ONLY**!
        self.clear_all_events(Some(linked_chunk_ids_for_room_1[0].room_id())).await.unwrap();

        // Check all data have been removed for room 1 **ONLY**, forever.
        for linked_chunk_id in linked_chunk_ids_for_room_1 {
            let room_id = linked_chunk_id.room_id();

            // No more linked chunks!
            assert!(
                lazy_loader::from_all_chunks::<3, _, _>(
                    self.load_all_chunks(linked_chunk_id).await.unwrap()
                )
                .unwrap()
                .is_none()
            );

            // No more events!
            assert!(self.get_room_events(room_id, None, None).await.unwrap().is_empty());
        }

        // Check all the other data are untouched.
        for linked_chunk_id in
            linked_chunk_ids_for_room_0.iter().chain(&linked_chunk_ids_for_room_2)
        {
            let room_id = linked_chunk_id.room_id();

            // Linked chunks all exist!
            assert!(
                lazy_loader::from_all_chunks::<3, _, _>(
                    self.load_all_chunks(*linked_chunk_id).await.unwrap()
                )
                .unwrap()
                .is_some()
            );

            // Events exist!
            assert_eq!(self.get_room_events(room_id, None, None).await.unwrap().len(), 3);
        }
    }

    async fn test_filter_duplicated_events(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let linked_chunk_id = LinkedChunkId::Room(room_id);
        let another_room_id = room_id!("!r1:matrix.org");
        let another_linked_chunk_id = LinkedChunkId::Room(another_room_id);
        let event = |msg: &str| make_test_event(room_id, msg);

        let event_comte = event("comté");
        let event_brigand = event("brigand du jorat");
        let event_raclette = event("raclette");
        let event_morbier = event("morbier");
        let event_gruyere = event("gruyère");
        let event_tome = event("tome");
        let event_mont_dor = event("mont d'or");

        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![event_comte.clone(), event_brigand.clone()],
                },
                Update::NewGapChunk {
                    previous: Some(CId::new(0)),
                    new: CId::new(1),
                    next: None,
                    gap: Gap { token: "brillat-savarin".to_owned() },
                },
                Update::NewItemsChunk { previous: Some(CId::new(1)), new: CId::new(2), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(2), 0),
                    items: vec![event_morbier.clone(), event_mont_dor.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Add other events in another room, to ensure filtering take the `room_id` into
        // account.
        self.handle_linked_chunk_updates(
            another_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![event_tome.clone()],
                },
            ],
        )
        .await
        .unwrap();

        let duplicated_events = BTreeMap::from_iter(
            self.filter_duplicated_events(
                linked_chunk_id,
                vec![
                    event_comte.event_id().unwrap().to_owned(),
                    event_raclette.event_id().unwrap().to_owned(),
                    event_morbier.event_id().unwrap().to_owned(),
                    event_gruyere.event_id().unwrap().to_owned(),
                    event_tome.event_id().unwrap().to_owned(),
                    event_mont_dor.event_id().unwrap().to_owned(),
                ],
            )
            .await
            .unwrap(),
        );

        assert_eq!(duplicated_events.len(), 3);

        assert_eq!(
            *duplicated_events.get(event_comte.event_id().unwrap()).unwrap(),
            Position::new(CId::new(0), 0)
        );
        assert_eq!(
            *duplicated_events.get(event_morbier.event_id().unwrap()).unwrap(),
            Position::new(CId::new(2), 0)
        );
        assert_eq!(
            *duplicated_events.get(event_mont_dor.event_id().unwrap()).unwrap(),
            Position::new(CId::new(2), 1)
        );
    }

    async fn test_filter_duplicate_events_no_events(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let linked_chunk_id = LinkedChunkId::Room(room_id);
        let duplicates = self.filter_duplicated_events(linked_chunk_id, Vec::new()).await.unwrap();
        assert!(duplicates.is_empty());
    }

    async fn test_find_event(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let another_room_id = room_id!("!r1:matrix.org");
        let another_linked_chunk_id = LinkedChunkId::Room(another_room_id);
        let event = |msg: &str| make_test_event(room_id, msg);

        let event_comte = event("comté");
        let event_gruyere = event("gruyère");

        // Add one event in one room.
        self.handle_linked_chunk_updates(
            LinkedChunkId::Room(room_id),
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![event_comte.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Add another event in another room.
        self.handle_linked_chunk_updates(
            another_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![event_gruyere.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Now let's find the event.
        let event = self
            .find_event(room_id, event_comte.event_id().unwrap())
            .await
            .expect("failed to query for finding an event")
            .expect("failed to find an event");

        assert_eq!(event.event_id(), event_comte.event_id());

        // Now let's try to find an event that exists, but not in the expected room.
        assert!(
            self.find_event(room_id, event_gruyere.event_id().unwrap())
                .await
                .expect("failed to query for finding an event")
                .is_none()
        );

        // Clearing the rooms also clears the event's storage.
        self.clear_all_events(None).await.expect("failed to clear all rooms chunks");
        assert!(
            self.find_event(room_id, event_comte.event_id().unwrap())
                .await
                .expect("failed to query for finding an event")
                .is_none()
        );
    }

    async fn test_find_event_when_event_in_room_and_thread(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let thread_root = event_id!("$thread_root");

        // Create an event that will be only be inserted into the room
        let room_event_id = event_id!("$room_event");
        let room_event = make_test_event_with_event_id(room_id, "room event", Some(room_event_id));

        // Create an event that will only be inserted into the thread
        let thread_event_id = event_id!("$thread_event");
        let thread_event =
            make_test_event_with_event_id(room_id, "thread event", Some(thread_event_id));

        // Create an event that will be inserted into both the room and thread linked
        // chunks.
        let room_and_thread_event_id = event_id!("$room_and_thread");
        let room_and_thread_event = make_test_event_with_event_id(
            room_id,
            "room and thread",
            Some(room_and_thread_event_id),
        );

        let room_linked_chunk_id = LinkedChunkId::Room(room_id);
        let thread_linked_chunk_id = LinkedChunkId::Thread(room_id, thread_root);

        // Insert the relevant events into the room's linked chunk.
        self.handle_linked_chunk_updates(
            room_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(1), 0),
                    items: vec![room_event, room_and_thread_event.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Insert the relevant events into the thread's linked chunk.
        self.handle_linked_chunk_updates(
            thread_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(1), 0),
                    items: vec![thread_event, room_and_thread_event],
                },
            ],
        )
        .await
        .unwrap();

        // Verify that event that is only in the room can be retrieved
        assert_matches!(self.find_event(room_id, room_event_id).await, Ok(Some(event)) => {
            assert_eq!(event.event_id().unwrap(), room_event_id)
        });

        // Verify that the event that is only in the thread can be retrieved
        assert_matches!(self.find_event(room_id, thread_event_id).await, Ok(Some(event)) => {
            assert_eq!(event.event_id().unwrap(), thread_event_id)
        });

        // Verify that event that is in both room and thread can be retrieved
        assert_matches!(self.find_event(room_id, room_and_thread_event_id).await, Ok(Some(event)) => {
            assert_eq!(event.event_id().unwrap(), room_and_thread_event_id);
        });
    }

    async fn test_find_event_relations(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let another_room_id = room_id!("!r1:matrix.org");

        let f = EventFactory::new().room(room_id).sender(*ALICE);

        // Create event and related events for the first room.
        let eid1 = event_id!("$event1:matrix.org");
        let e1 = f.text_msg("comter").event_id(eid1).into_event();

        let edit_eid1 = event_id!("$edit_event1:matrix.org");
        let edit_e1 = f
            .text_msg("* comté")
            .event_id(edit_eid1)
            .edit(eid1, RoomMessageEventContentWithoutRelation::text_plain("comté"))
            .into_event();

        let reaction_eid1 = event_id!("$reaction_event1:matrix.org");
        let reaction_e1 = f.reaction(eid1, "👍").event_id(reaction_eid1).into_event();

        let eid2 = event_id!("$event2:matrix.org");
        let e2 = f.text_msg("galette saucisse").event_id(eid2).into_event();

        // Create events for the second room.
        let f = f.room(another_room_id);

        let eid3 = event_id!("$event3:matrix.org");
        let e3 = f.text_msg("gruyère").event_id(eid3).into_event();

        let reaction_eid3 = event_id!("$reaction_event3:matrix.org");
        let reaction_e3 = f.reaction(eid3, "👍").event_id(reaction_eid3).into_event();

        // Save All The Things!
        self.save_event(room_id, e1).await.unwrap();
        self.save_event(room_id, edit_e1).await.unwrap();
        self.save_event(room_id, reaction_e1.clone()).await.unwrap();
        self.save_event(room_id, e2).await.unwrap();
        self.save_event(another_room_id, e3).await.unwrap();
        self.save_event(another_room_id, reaction_e3).await.unwrap();

        // Finding relations without a filter returns all of them.
        let relations = self.find_event_relations(room_id, eid1, None).await.unwrap();
        assert_eq!(relations.len(), 2);
        // The position is `None` for items outside the linked chunk.
        assert!(
            relations.iter().any(|(ev, pos)| ev.event_id() == Some(edit_eid1) && pos.is_none())
        );
        assert!(
            relations.iter().any(|(ev, pos)| ev.event_id() == Some(reaction_eid1) && pos.is_none())
        );

        // Finding relations with a filter only returns a subset.
        let relations = self
            .find_event_relations(room_id, eid1, Some(&[RelationType::Replacement]))
            .await
            .unwrap();
        assert_eq!(relations.len(), 1);
        assert_eq!(relations[0].0.event_id(), Some(edit_eid1));

        let relations = self
            .find_event_relations(
                room_id,
                eid1,
                Some(&[RelationType::Replacement, RelationType::Annotation]),
            )
            .await
            .unwrap();
        assert_eq!(relations.len(), 2);
        assert!(relations.iter().any(|r| r.0.event_id() == Some(edit_eid1)));
        assert!(relations.iter().any(|r| r.0.event_id() == Some(reaction_eid1)));

        // We can't find relations using the wrong room.
        let relations = self
            .find_event_relations(another_room_id, eid1, Some(&[RelationType::Replacement]))
            .await
            .unwrap();
        assert!(relations.is_empty());

        // But if an event exists in the linked chunk, we may have its position when
        // it's found as a relationship.

        // Add reaction_e1 to the room's linked chunk.
        self.handle_linked_chunk_updates(
            LinkedChunkId::Room(room_id),
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems { at: Position::new(CId::new(0), 0), items: vec![reaction_e1] },
            ],
        )
        .await
        .unwrap();

        // When looking for aggregations to e1, we should have the position for
        // reaction_e1.
        let relations = self.find_event_relations(room_id, eid1, None).await.unwrap();

        // The position is set for `reaction_eid1` now.
        assert!(relations.iter().any(|(ev, pos)| {
            ev.event_id() == Some(reaction_eid1) && *pos == Some(Position::new(CId::new(0), 0))
        }));

        // But it's still not set for the other related events.
        assert!(
            relations.iter().any(|(ev, pos)| ev.event_id() == Some(edit_eid1) && pos.is_none())
        );
    }

    async fn test_find_event_relations_when_event_in_room_and_thread(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let thread_root = event_id!("$thread_root");

        // Create an event that will inserted into both the room and thread linked
        // chunks.
        let event_id = event_id!("$event");
        let event = make_test_event_with_event_id(room_id, "event", Some(event_id));

        // Create an event that will only be inserted into the thread in order to help
        // distinguish between the room and thread linked chunks.
        let extra_thread_event_id = event_id!("$extra_thread_event");
        let extra_thread_event = make_test_event_with_event_id(
            room_id,
            "extra thread event",
            Some(extra_thread_event_id),
        );

        // Create a reaction that will only be inserted into the room
        let room_reaction_id = event_id!("$room_reaction");
        let room_reaction = EventFactory::new()
            .room(room_id)
            .sender(*ALICE)
            .reaction(event_id, "room")
            .event_id(room_reaction_id)
            .into_event();

        // Create a reaction that will only be inserted into the thread
        let thread_reaction_id = event_id!("$thread_reaction");
        let thread_reaction = EventFactory::new()
            .room(room_id)
            .sender(*ALICE)
            .reaction(event_id, "thread")
            .event_id(thread_reaction_id)
            .into_event();

        // Create a reaction that will be inserted into both the room and thread linked
        // chunks.
        let room_and_thread_reaction_id = event_id!("$room_and_thread_reaction");
        let room_and_thread_reaction = EventFactory::new()
            .room(room_id)
            .sender(*ALICE)
            .reaction(event_id, "room and thread")
            .event_id(room_and_thread_reaction_id)
            .into_event();

        let room_linked_chunk_id = LinkedChunkId::Room(room_id);
        let thread_linked_chunk_id = LinkedChunkId::Thread(room_id, thread_root);

        // Insert the relevant events into the room's linked chunk.
        self.handle_linked_chunk_updates(
            room_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(1), 0),
                    items: vec![event.clone(), room_reaction, room_and_thread_reaction.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Insert the relevant events into the thread's linked chunk.
        self.handle_linked_chunk_updates(
            thread_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(1), 0),
                    items: vec![
                        event.clone(),
                        extra_thread_event,
                        thread_reaction,
                        room_and_thread_reaction,
                    ],
                },
            ],
        )
        .await
        .unwrap();

        // Verify that only related events from the room are returned
        assert_matches!(self.find_event_relations(room_id, event_id, None).await, Ok(relations) => {
            assert_eq!(relations.len(), 3);
            // Verify that room reaction is in the list and associated with its
            // position in the room linked chunk.
            let room_relation = relations
                .iter()
                .find(|relation| relation.0.event_id().unwrap() == room_reaction_id)
                .unwrap();
            assert_matches!(room_relation, (_, Some(position)) => {
                assert_eq!(*position, Position::new(CId::new(1), 1));
            });

            // Verify that thread reaction is in the list and not associated with a
            // position, as all positions are provided for the room linked chunk.
            let thread_relation = relations
                .iter()
                .find(|relation| relation.0.event_id().unwrap() == thread_reaction_id)
                .unwrap();
            assert_matches!(thread_relation, (_, None));

            // Verify that room and thread reaction is in the list and associated
            // with its position in the room linked chunk, not the thread linked chunk.
            let room_and_thread_relation = relations
                .iter()
                .find(|relation| relation.0.event_id().unwrap() == room_and_thread_reaction_id)
                .unwrap();
            assert_matches!(room_and_thread_relation, (_, Some(position)) => {
                assert_eq!(*position, Position::new(CId::new(1), 2));
            });
        });
    }

    async fn test_get_room_events(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let another_room_id = room_id!("!r1:matrix.org");
        let linked_chunk_id = LinkedChunkId::Room(room_id);
        let another_linked_chunk_id = LinkedChunkId::Room(another_room_id);
        let event = |msg: &str| make_test_event(room_id, msg);

        let event_comte = event("comté");
        let event_gruyere = event("gruyère");
        let event_stilton = event("stilton");

        // Add one event in one room.
        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![event_comte.clone(), event_gruyere.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Add an event in a different room.
        self.handle_linked_chunk_updates(
            another_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![event_stilton.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Now let's find the events.
        let events = self
            .get_room_events(room_id, None, None)
            .await
            .expect("failed to query for room events");

        assert_eq!(events.len(), 2);

        let got_ids: Vec<_> =
            events.into_iter().map(|ev| ev.event_id().map(ToOwned::to_owned)).collect();
        let expected_ids = vec![
            event_comte.event_id().map(ToOwned::to_owned),
            event_gruyere.event_id().map(ToOwned::to_owned),
        ];

        for expected in expected_ids {
            assert!(
                got_ids.contains(&expected),
                "Expected event {expected:?} not in got events: {got_ids:?}."
            );
        }
    }

    async fn test_get_room_events_filtered(&self) {
        macro_rules! assert_expected_events {
            ($events:expr, [$($item:expr),* $(,)?]) => {{
                let got_ids: BTreeSet<_> = $events.into_iter().map(|ev| ev.event_id().map(ToOwned::to_owned)).flatten().collect();
                let expected_ids = BTreeSet::from([$($item.event_id().unwrap().to_owned()),*]);

                assert_eq!(got_ids, expected_ids);
            }};
        }

        let room_id = room_id!("!r0:matrix.org");
        let linked_chunk_id = LinkedChunkId::Room(room_id);
        let another_room_id = room_id!("!r1:matrix.org");
        let another_linked_chunk_id = LinkedChunkId::Room(another_room_id);

        let event = |session_id: &str| make_encrypted_test_event(room_id, session_id);

        let first_event = event("session_1");
        let second_event = event("session_2");
        let third_event = event("session_3");
        let fourth_event = make_test_event(room_id, "It's a secret to everybody");

        // Add one event in one room.
        self.handle_linked_chunk_updates(
            linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![first_event.clone(), second_event.clone(), fourth_event.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Add an event in a different room.
        self.handle_linked_chunk_updates(
            another_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![third_event.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Now let's find all the encrypted events of the first room.
        let events = self
            .get_room_events(room_id, Some("m.room.encrypted"), None)
            .await
            .expect("failed to query for room events");

        assert_eq!(events.len(), 2);
        assert_expected_events!(events, [first_event, second_event]);

        // Now let's find all the encrypted events which were encrypted using the first
        // session ID.
        let events = self
            .get_room_events(room_id, Some("m.room.encrypted"), Some("session_1"))
            .await
            .expect("failed to query for room events");

        assert_eq!(events.len(), 1);
        assert_expected_events!(events, [first_event]);
    }

    async fn test_get_room_events_with_event_in_room_and_thread(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let thread_root = event_id!("$thread_root");

        // Create an event that will be only be inserted into the room
        let room_event_id = event_id!("$room_event");
        let room_event = make_test_event_with_event_id(room_id, "room event", Some(room_event_id));

        // Create an event that will only be inserted into the thread. This may not be a
        // sensible operation in practice, as threads seem to always exist in a
        // room, but let's test it anyway.
        let thread_event_id = event_id!("$thread_event");
        let thread_event =
            make_test_event_with_event_id(room_id, "thread event", Some(thread_event_id));

        // Create an event that will be inserted into both the room and thread linked
        // chunks.
        let room_and_thread_event_id = event_id!("$room_and_thread");
        let room_and_thread_event = make_test_event_with_event_id(
            room_id,
            "room and thread",
            Some(room_and_thread_event_id),
        );

        let room_linked_chunk_id = LinkedChunkId::Room(room_id);
        let thread_linked_chunk_id = LinkedChunkId::Thread(room_id, thread_root);

        // Insert the relevant events into the room's linked chunk.
        self.handle_linked_chunk_updates(
            room_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(1), 0),
                    items: vec![room_event, room_and_thread_event.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Insert the relevant events into the thread's linked chunk.
        self.handle_linked_chunk_updates(
            thread_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(1), 0),
                    items: vec![thread_event, room_and_thread_event],
                },
            ],
        )
        .await
        .unwrap();

        // Verify that all events can be retrieved and none are duplicated in the
        // returned list.
        let expected_event_ids =
            BTreeSet::from([room_event_id, thread_event_id, room_and_thread_event_id]);
        assert_matches!(self.get_room_events(room_id, None, None).await, Ok(events) => {
            assert_eq!(events.len(), 3);
            assert!(events.iter().all(|event| {
                expected_event_ids.contains(event.event_id().unwrap())
            }));
        });
    }

    async fn test_save_event(&self) {
        let room_id = room_id!("!r0:matrix.org");
        let another_room_id = room_id!("!r1:matrix.org");

        let event = |msg: &str| make_test_event(room_id, msg);
        let event_comte = event("comté");
        let event_gruyere = event("gruyère");

        // Add one event in one room.
        self.save_event(room_id, event_comte.clone()).await.unwrap();

        // Add another event in another room.
        self.save_event(another_room_id, event_gruyere.clone()).await.unwrap();

        // Events can be found, when searched in their own rooms.
        let event = self
            .find_event(room_id, event_comte.event_id().unwrap())
            .await
            .expect("failed to query for finding an event")
            .expect("failed to find an event");
        assert_eq!(event.event_id(), event_comte.event_id());

        let event = self
            .find_event(another_room_id, event_gruyere.event_id().unwrap())
            .await
            .expect("failed to query for finding an event")
            .expect("failed to find an event");
        assert_eq!(event.event_id(), event_gruyere.event_id());

        // But they won't be returned when searching in the wrong room.
        assert!(
            self.find_event(another_room_id, event_comte.event_id().unwrap())
                .await
                .expect("failed to query for finding an event")
                .is_none()
        );
        assert!(
            self.find_event(room_id, event_gruyere.event_id().unwrap())
                .await
                .expect("failed to query for finding an event")
                .is_none()
        );
    }

    async fn test_save_event_updates_event_in_room_and_thread(&self) {
        let room_id = *DEFAULT_TEST_ROOM_ID;
        let thread_root = event_id!("$thread_root");

        // Create an event that will be inserted into both the room and thread linked
        // chunks.
        let event_id = event_id!("$event");
        let event = make_test_event_with_event_id(room_id, "event", Some(event_id));

        let room_linked_chunk_id = LinkedChunkId::Room(room_id);
        let thread_linked_chunk_id = LinkedChunkId::Thread(room_id, thread_root);

        // Insert the relevant events into the room's linked chunk.
        self.handle_linked_chunk_updates(
            room_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems { at: Position::new(CId::new(1), 0), items: vec![event.clone()] },
            ],
        )
        .await
        .unwrap();

        // Insert the relevant events into the thread's linked chunk.
        self.handle_linked_chunk_updates(
            thread_linked_chunk_id,
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(1), next: None },
                Update::PushItems { at: Position::new(CId::new(1), 0), items: vec![event.clone()] },
            ],
        )
        .await
        .unwrap();

        // Save updated version of original event, which should replace the content of
        // the existing event
        let updated_content = "updated content";
        let updated = make_test_event_with_event_id(room_id, updated_content, Some(event_id));
        self.save_event(room_id, updated).await.unwrap();

        // Load all chunks from both room and thread
        let room_chunks = self.load_all_chunks(room_linked_chunk_id).await.unwrap();
        let thread_chunks = self.load_all_chunks(thread_linked_chunk_id).await.unwrap();

        assert_eq!(room_chunks.len(), 1);
        assert_eq!(thread_chunks.len(), 1);

        // Verify the event has been updated in both room and thread
        assert_matches!(&room_chunks[0].content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 1);
            assert_eq!(events[0].event_id(), Some(event_id));
            check_test_event(&events[0], updated_content);
        });
        assert_matches!(&thread_chunks[0].content, ChunkContent::Items(events) => {
            assert_eq!(events.len(), 1);
            assert_eq!(events[0].event_id(), Some(event_id));
            check_test_event(&events[0], updated_content);
        });
    }

    async fn test_thread_vs_room_linked_chunk(&self) {
        let room_id = room_id!("!r0:matrix.org");

        let event = |msg: &str| make_test_event(room_id, msg);

        let thread1_ev = event("comté");
        let thread2_ev = event("gruyère");
        let thread2_ev2 = event("beaufort");
        let room_ev = event("brillat savarin triple crème");

        let thread_root1 = event("thread1");
        let thread_root2 = event("thread2");

        // Add one event in a thread linked chunk.
        self.handle_linked_chunk_updates(
            LinkedChunkId::Thread(room_id, thread_root1.event_id().unwrap()),
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![thread1_ev.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Add one event in another thread linked chunk (same room).
        self.handle_linked_chunk_updates(
            LinkedChunkId::Thread(room_id, thread_root2.event_id().unwrap()),
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![thread2_ev.clone(), thread2_ev2.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // Add another event to the room linked chunk.
        self.handle_linked_chunk_updates(
            LinkedChunkId::Room(room_id),
            vec![
                Update::NewItemsChunk { previous: None, new: CId::new(0), next: None },
                Update::PushItems {
                    at: Position::new(CId::new(0), 0),
                    items: vec![room_ev.clone()],
                },
            ],
        )
        .await
        .unwrap();

        // All the events can be found with `find_event()` for the room.
        self.find_event(room_id, thread2_ev.event_id().unwrap())
            .await
            .expect("failed to query for finding an event")
            .expect("failed to find thread1_ev");

        self.find_event(room_id, thread2_ev.event_id().unwrap())
            .await
            .expect("failed to query for finding an event")
            .expect("failed to find thread2_ev");

        self.find_event(room_id, thread2_ev2.event_id().unwrap())
            .await
            .expect("failed to query for finding an event")
            .expect("failed to find thread2_ev2");

        self.find_event(room_id, room_ev.event_id().unwrap())
            .await
            .expect("failed to query for finding an event")
            .expect("failed to find room_ev");

        // Finding duplicates operates based on the linked chunk id.
        let dups = self
            .filter_duplicated_events(
                LinkedChunkId::Thread(room_id, thread_root1.event_id().unwrap()),
                vec![
                    thread1_ev.event_id().unwrap().to_owned(),
                    room_ev.event_id().unwrap().to_owned(),
                ],
            )
            .await
            .unwrap();
        assert_eq!(dups.len(), 1);
        assert_eq!(dups[0].0, thread1_ev.event_id().unwrap());

        // Loading all chunks operates based on the linked chunk id.
        let all_chunks = self
            .load_all_chunks(LinkedChunkId::Thread(room_id, thread_root2.event_id().unwrap()))
            .await
            .unwrap();
        assert_eq!(all_chunks.len(), 1);
        assert_eq!(all_chunks[0].identifier, CId::new(0));
        assert_let!(ChunkContent::Items(observed_items) = all_chunks[0].content.clone());
        assert_eq!(observed_items.len(), 2);
        assert_eq!(observed_items[0].event_id(), thread2_ev.event_id());
        assert_eq!(observed_items[1].event_id(), thread2_ev2.event_id());

        // Loading the metadata of all chunks operates based on the linked chunk
        // id.
        let metas = self
            .load_all_chunks_metadata(LinkedChunkId::Thread(
                room_id,
                thread_root2.event_id().unwrap(),
            ))
            .await
            .unwrap();
        assert_eq!(metas.len(), 1);
        assert_eq!(metas[0].identifier, CId::new(0));
        assert_eq!(metas[0].num_items, 2);

        // Loading the last chunk operates based on the linked chunk id.
        let (last_chunk, _chunk_identifier_generator) = self
            .load_last_chunk(LinkedChunkId::Thread(room_id, thread_root1.event_id().unwrap()))
            .await
            .unwrap();
        let last_chunk = last_chunk.unwrap();
        assert_eq!(last_chunk.identifier, CId::new(0));
        assert_let!(ChunkContent::Items(observed_items) = last_chunk.content);
        assert_eq!(observed_items.len(), 1);
        assert_eq!(observed_items[0].event_id(), thread1_ev.event_id());
    }
}

/// Macro building to allow your `EventCacheStore` implementation to run the
/// entire tests suite locally.
///
/// You need to provide a `async fn get_event_cache_store() ->
/// EventCacheStoreResult<impl EventCacheStore>` providing a fresh event cache
/// store on the same level you invoke the macro.
///
/// ## Usage Example:
/// ```no_run
/// # use matrix_sdk_base::event_cache::store::{
/// #    EventCacheStore,
/// #    MemoryStore as MyStore,
/// #    Result as EventCacheStoreResult,
/// # };
///
/// #[cfg(test)]
/// mod tests {
///     use super::{EventCacheStore, EventCacheStoreResult, MyStore};
///
///     async fn get_event_cache_store()
///     -> EventCacheStoreResult<impl EventCacheStore> {
///         Ok(MyStore::new())
///     }
///
///     event_cache_store_integration_tests!();
/// }
/// ```
#[allow(unused_macros, unused_extern_crates)]
#[macro_export]
macro_rules! event_cache_store_integration_tests {
    () => {
        mod event_cache_store_integration_tests {
            use matrix_sdk_test::async_test;
            use $crate::event_cache::store::{
                EventCacheStoreIntegrationTests, IntoEventCacheStore,
            };

            use super::get_event_cache_store;

            #[async_test]
            async fn test_handle_updates_and_rebuild_linked_chunk() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_handle_updates_and_rebuild_linked_chunk().await;
            }

            #[async_test]
            async fn test_linked_chunk_exists_before_referenced() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_exists_before_referenced().await;
            }

            #[async_test]
            async fn test_linked_chunk_allow_same_event_in_room_and_thread() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_allows_same_event_in_room_and_thread().await;
            }

            #[async_test]
            async fn test_load_last_chunk() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_load_last_chunk().await;
            }

            #[async_test]
            async fn test_load_last_chunk_with_a_cycle() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_load_last_chunk_with_a_cycle().await;
            }

            #[async_test]
            async fn test_load_previous_chunk() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_load_previous_chunk().await;
            }

            #[async_test]
            async fn test_linked_chunk_incremental_loading() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_incremental_loading().await;
            }

            #[async_test]
            async fn test_linked_chunk_remove_chunk() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_remove_chunk().await;
            }

            #[async_test]
            async fn test_linked_chunk_push_items() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_push_items().await;
            }

            #[async_test]
            async fn test_linked_chunk_replace_item() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_replace_item().await;
            }

            #[async_test]
            async fn test_linked_chunk_remove_item() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_remove_item().await;
            }

            #[async_test]
            async fn test_linked_chunk_detach_last_items() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_detach_last_items().await;
            }

            #[async_test]
            async fn test_linked_chunk_start_end_reattach_items() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_start_end_reattach_items().await;
            }

            #[async_test]
            async fn test_linked_chunk_clear() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_clear().await;
            }

            #[async_test]
            async fn test_linked_chunk_clear_and_reinsert() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_clear_and_reinsert().await;
            }

            #[async_test]
            async fn test_rebuild_empty_linked_chunk() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_rebuild_empty_linked_chunk().await;
            }

            #[async_test]
            async fn test_linked_chunk_multiple_rooms() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_linked_chunk_multiple_rooms().await;
            }

            #[async_test]
            async fn test_load_all_chunks_metadata() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_load_all_chunks_metadata().await;
            }

            #[async_test]
            async fn test_load_and_update_thread_info() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_load_and_update_thread_info().await;
            }

            #[async_test]
            async fn test_clear_all_events() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_clear_all_events().await;
            }

            #[async_test]
            async fn test_clear_all_events_for_specific_room() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_clear_all_events_for_specific_room().await;
            }

            #[async_test]
            async fn test_filter_duplicated_events() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_filter_duplicated_events().await;
            }

            #[async_test]
            async fn test_filter_duplicate_events_no_events() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_filter_duplicate_events_no_events().await;
            }

            #[async_test]
            async fn test_find_event() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_find_event().await;
            }

            #[async_test]
            async fn test_find_event_when_event_in_room_and_thread() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_find_event_when_event_in_room_and_thread().await;
            }

            #[async_test]
            async fn test_find_event_relations() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_find_event_relations().await;
            }

            #[async_test]
            async fn test_find_event_relations_when_event_in_room_and_thread() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_find_event_relations_when_event_in_room_and_thread().await;
            }

            #[async_test]
            async fn test_get_room_events() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_get_room_events().await;
            }

            #[async_test]
            async fn test_get_room_events_filtered() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_get_room_events_filtered().await;
            }

            #[async_test]
            async fn test_get_room_events_with_event_in_room_and_thread() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_get_room_events_with_event_in_room_and_thread().await;
            }

            #[async_test]
            async fn test_save_event() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_save_event().await;
            }

            #[async_test]
            async fn test_save_event_updates_event_in_room_and_thread() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_save_event_updates_event_in_room_and_thread().await;
            }

            #[async_test]
            async fn test_thread_vs_room_linked_chunk() {
                let event_cache_store =
                    get_event_cache_store().await.unwrap().into_event_cache_store();
                event_cache_store.test_thread_vs_room_linked_chunk().await;
            }
        }
    };
}

/// Macro generating tests for the event cache store, related to time (mostly
/// for the cross-process lock).
#[allow(unused_macros)]
#[macro_export]
macro_rules! event_cache_store_integration_tests_time {
    () => {
        mod event_cache_store_integration_tests_time {
            use std::time::Duration;

            #[cfg(all(target_family = "wasm", target_os = "unknown"))]
            use gloo_timers::future::sleep;
            use matrix_sdk_test::async_test;
            #[cfg(not(all(target_family = "wasm", target_os = "unknown")))]
            use tokio::time::sleep;
            use $crate::event_cache::store::IntoEventCacheStore;

            use super::get_event_cache_store;

            #[async_test]
            async fn test_lease_locks() {
                let store = get_event_cache_store().await.unwrap().into_event_cache_store();

                let acquired0 = store.try_take_leased_lock(0, "key", "alice").await.unwrap();
                assert_eq!(acquired0, Some(1)); // first lock generation

                // Should extend the lease automatically (same holder).
                let acquired2 = store.try_take_leased_lock(300, "key", "alice").await.unwrap();
                assert_eq!(acquired2, Some(1)); // same lock generation

                // Should extend the lease automatically (same holder + time is ok).
                let acquired3 = store.try_take_leased_lock(300, "key", "alice").await.unwrap();
                assert_eq!(acquired3, Some(1)); // same lock generation

                // Another attempt at taking the lock should fail, because it's taken.
                let acquired4 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
                assert!(acquired4.is_none()); // not acquired

                // Even if we insist.
                let acquired5 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
                assert!(acquired5.is_none()); // not acquired

                // That's a nice test we got here, go take a little nap.
                sleep(Duration::from_millis(50)).await;

                // Still too early.
                let acquired55 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
                assert!(acquired55.is_none()); // not acquired

                // Ok you can take another nap then.
                sleep(Duration::from_millis(250)).await;

                // At some point, we do get the lock.
                let acquired6 = store.try_take_leased_lock(0, "key", "bob").await.unwrap();
                assert_eq!(acquired6, Some(2)); // new lock generation!

                sleep(Duration::from_millis(1)).await;

                // The other gets it almost immediately too.
                let acquired7 = store.try_take_leased_lock(0, "key", "alice").await.unwrap();
                assert_eq!(acquired7, Some(3)); // new lock generation!

                sleep(Duration::from_millis(1)).await;

                // But when we take a longer lease…
                let acquired8 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
                assert_eq!(acquired8, Some(4)); // new lock generation!

                // It blocks the other user.
                let acquired9 = store.try_take_leased_lock(300, "key", "alice").await.unwrap();
                assert!(acquired9.is_none()); // not acquired

                // We can hold onto our lease.
                let acquired10 = store.try_take_leased_lock(300, "key", "bob").await.unwrap();
                assert_eq!(acquired10, Some(4)); // same lock generation
            }
        }
    };
}