cachekit-rs 0.9.0

//! Intent-based cache presets.
//!
//! Pre-configured factory methods that build a [`CacheKit`] client from a
//! single declarative call. Each intent sets sensible defaults for a specific
//! use case and returns a [`CacheKitBuilder`] so callers can override any
//! setting before building.
//!
//! The preset matrix and per-intent resilience contract live in the
//! crate-level docs (`lib.rs`) — the single rustdoc-rendered copy. This
//! module is private, so docs here reach source readers only; the per-method
//! docs below are what docs.rs renders.
//!
//! Reliability defaults come from
//! [`ReliabilityConfig::default()`](crate::reliability::ReliabilityConfig)
//! (requires the `reliability` feature, on by default). Override via
//! [`CacheKitBuilder::reliability`];
//! [`ReliabilityConfig::disabled()`](crate::reliability::ReliabilityConfig::disabled)
//! turns the stack off entirely.

use std::time::Duration;

use crate::client::{CacheKit, CacheKitBuilder, SharedBackend};
use crate::error::CachekitError;

// ── SharedBackend wrapping ───────────────────────────────────────────────────

#[cfg(not(any(target_arch = "wasm32", feature = "unsync")))]
fn wrap(b: impl crate::backend::Backend + 'static) -> SharedBackend {
    std::sync::Arc::new(b)
}

#[cfg(any(target_arch = "wasm32", feature = "unsync"))]
fn wrap(b: impl crate::backend::Backend + 'static) -> SharedBackend {
    std::rc::Rc::new(b)
}

// ── Intent presets ───────────────────────────────────────────────────────────

/// `minimal` builder defaults, split from the eager Redis connect so the
/// L1-on / SWR-off contract (`protocol/spec/intent-presets.md` § L1 Posture)
/// is unit-testable without a live server.
#[cfg(feature = "redis")]
fn minimal_defaults(backend: SharedBackend) -> CacheKitBuilder {
    let builder = CacheKitBuilder::default()
        .backend(backend)
        .default_ttl(Duration::from_secs(300))
        .l1_capacity(1000);
    // Builder default is SWR-on; spec § L1 Posture says minimal MUST NOT.
    #[cfg(all(feature = "l1", not(feature = "unsync"), not(target_arch = "wasm32")))]
    let builder = builder.swr_enabled(false);
    builder
}

/// `secure` builder defaults, split from the eager Redis connect so the key
/// path is unit-testable without a live server. Takes hex-decoded key bytes
/// only (so `>= 32`, not the raw-bytes exactly-32 rule) and reads no
/// environment: [`CacheKit::secure`] passes no previous keys.
#[cfg(all(feature = "redis", feature = "encryption"))]
fn secure_defaults(
    master_key: &[u8],
    previous_keys: &[zeroize::Zeroizing<Vec<u8>>],
) -> Result<CacheKitBuilder, CachekitError> {
    let previous: Vec<&[u8]> = previous_keys.iter().map(|k| k.as_slice()).collect();
    let builder = CacheKitBuilder::default()
        .default_ttl(Duration::from_secs(600))
        .l1_capacity(1000)
        .encryption_from_hex_decoded(master_key, &previous, "default")?;
    #[cfg(all(feature = "reliability", not(target_arch = "wasm32")))]
    let builder = builder.reliability(crate::reliability::ReliabilityConfig::default());
    Ok(builder)
}

/// `CACHEKIT_MASTER_KEY` for [`CacheKit::secure_from_env`]; unset and empty
/// are both an error, never plaintext.
#[cfg(all(feature = "redis", feature = "encryption"))]
fn master_key_hex_from_env() -> Result<zeroize::Zeroizing<String>, CachekitError> {
    std::env::var("CACHEKIT_MASTER_KEY")
        .ok()
        .map(zeroize::Zeroizing::new)
        .filter(|k| !k.is_empty())
        .ok_or_else(|| {
            CachekitError::Config(
                "CACHEKIT_MASTER_KEY is unset or empty: set it to a 64-hex-char key or pass \
                 the key to CacheKit::secure(url, master_key_hex)"
                    .to_owned(),
            )
        })
}

/// The whole environment read of [`CacheKit::secure_from_env`] — the current
/// key and `CACHEKIT_PREVIOUS_MASTER_KEYS` — resolved into `secure` defaults
/// before any Redis I/O. Previous keys go through the same reader as
/// [`CachekitConfig::from_env`](crate::config::CachekitConfig::from_env).
#[cfg(all(feature = "redis", feature = "encryption"))]
fn secure_env_defaults() -> Result<CacheKitBuilder, CachekitError> {
    let master_key_hex = master_key_hex_from_env()?;
    let master_key = crate::config::decode_master_key_hex(&master_key_hex, "CACHEKIT_MASTER_KEY")?;
    let previous = crate::config::previous_master_keys_from_env(Some(&master_key))?;
    secure_defaults(&master_key, &previous)
}

/// Attach an eagerly connected, auto-reconnecting Redis backend to a
/// `secure` builder. Takes the builder, not the key, so key validation has
/// already happened: a bad key must not be masked by (or pay for) Redis I/O.
#[cfg(all(feature = "redis", feature = "encryption"))]
async fn connect_secure(
    redis_url: &str,
    builder: CacheKitBuilder,
) -> Result<CacheKitBuilder, CachekitError> {
    let backend = crate::backend::redis::RedisBackend::builder()
        .url(redis_url)
        .auto_reconnect()
        .build()?;
    drop(backend.connect().await?);
    Ok(builder.backend(wrap(backend)))
}

impl CacheKit {
    /// **Minimal** — speed-first Redis cache, no extras.
    ///
    /// * Backend: Redis (connects eagerly; **fails fast** — a dropped
    ///   connection is not re-established)
    /// * L1 cache: **on** (1 000 entries, **no SWR / invalidation**) — an L1
    ///   hit is served as-is until it expires, so a read may return an entry
    ///   up to its TTL (300 s by default) after another process changed it
    ///   in Redis. Chain
    ///   [`.no_l1()`](CacheKitBuilder::no_l1) to read through every time.
    /// * Encryption: **no**
    /// * Reliability: **off** — no retry, no circuit breaker, no
    ///   backpressure; every backend error propagates on first failure and
    ///   backend concurrency is unbounded
    /// * Default TTL: **300 s**
    ///
    /// Good for: product catalogs, public data, development.
    ///
    /// # Errors
    ///
    /// Returns [`CachekitError`] if the URL is invalid or Redis is unreachable.
    ///
    /// # Example
    ///
    /// ```no_run
    /// # async fn example() -> Result<(), cachekit::CachekitError> {
    /// let cache = cachekit::CacheKit::minimal("redis://localhost:6379").await?
    ///     .namespace("myapp")
    ///     .build()?;
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(feature = "redis")]
    pub async fn minimal(redis_url: &str) -> Result<CacheKitBuilder, CachekitError> {
        let backend = crate::backend::redis::RedisBackend::builder()
            .url(redis_url)
            .build()?;
        drop(backend.connect().await?);

        Ok(minimal_defaults(wrap(backend)))
    }

    /// **Production** — reliability-first Redis cache with L1.
    ///
    /// * Backend: Redis (connects eagerly, failing fast if unreachable;
    ///   **auto-reconnects** after a dropped connection with exponential
    ///   backoff, 100 ms → 30 s, retrying indefinitely)
    /// * L1 cache: **on** (1 000 entries)
    /// * Encryption: **no**
    /// * Reliability: **on** — retry with backoff + jitter, circuit
    ///   breaker, backpressure (max 100 concurrent backend ops)
    /// * Default TTL: **600 s**
    ///
    /// Good for: user sessions, API responses, production services.
    ///
    /// # Errors
    ///
    /// Returns [`CachekitError`] if the URL is invalid or Redis is unreachable.
    ///
    /// # Example
    ///
    /// ```no_run
    /// # async fn example() -> Result<(), cachekit::CachekitError> {
    /// let cache = cachekit::CacheKit::production("redis://localhost:6379").await?
    ///     .namespace("api")
    ///     .build()?;
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(feature = "redis")]
    pub async fn production(redis_url: &str) -> Result<CacheKitBuilder, CachekitError> {
        let backend = crate::backend::redis::RedisBackend::builder()
            .url(redis_url)
            .auto_reconnect()
            .build()?;
        drop(backend.connect().await?);

        let builder = CacheKitBuilder::default()
            .backend(wrap(backend))
            .default_ttl(Duration::from_secs(600))
            .l1_capacity(1000);
        #[cfg(all(feature = "reliability", not(target_arch = "wasm32")))]
        let builder = builder.reliability(crate::reliability::ReliabilityConfig::default());
        Ok(builder)
    }

    /// **Secure** — zero-knowledge encrypted Redis cache.
    ///
    /// * Backend: Redis (connects eagerly, failing fast if unreachable;
    ///   **auto-reconnects** after a dropped connection with exponential
    ///   backoff, 100 ms → 30 s, retrying indefinitely)
    /// * L1 cache: **on** (1 000 entries, stores ciphertext)
    /// * Encryption: **AES-256-GCM** with HKDF-SHA256
    /// * Reliability: **on** — retry with backoff + jitter, circuit
    ///   breaker, backpressure (max 100 concurrent backend ops)
    /// * Default TTL: **600 s**
    /// * Tenant ID: `"default"` for both key derivation and AAD (override via
    ///   [`.encryption()`](CacheKitBuilder::encryption))
    ///
    /// Good for: PII, payments, GDPR/HIPAA-sensitive data.
    ///
    /// `master_key_hex` is the master key as a **hex string** — the same
    /// string `CACHEKIT_MASTER_KEY` holds, decoded to the same key bytes by
    /// every CacheKit SDK. This is the cross-SDK-portable key path. Use
    /// exactly **32 bytes (64 hex chars)**: shorter is rejected, and longer
    /// is accepted here but not by every SDK. Generate one with
    /// `openssl rand -hex 32`.
    ///
    /// Use [`CacheKit::secure_from_env`] to read the key from
    /// `CACHEKIT_MASTER_KEY`. There is no raw-bytes preset: exactly 32
    /// decoded key bytes go to [`CacheKitBuilder::encryption_from_bytes`],
    /// which rejects any other length — including the 64 ASCII bytes of a
    /// hex string, which would derive a key no other SDK derives.
    ///
    /// The key is validated **before** any Redis connection is attempted — a
    /// bad key is a deterministic local error, never masked by (or paying
    /// for) network I/O.
    ///
    /// # Errors
    ///
    /// Returns [`CachekitError::Config`] if `master_key_hex` is not hex or
    /// decodes to fewer than 32 bytes, or if the URL is invalid; another
    /// [`CachekitError`] if Redis is unreachable.
    ///
    /// # Example
    ///
    /// ```no_run
    /// # async fn example() -> Result<(), Box<dyn std::error::Error>> {
    /// // 64 hex chars (32 bytes) from your secret store — `openssl rand -hex 32`.
    /// let master_key_hex = std::env::var("APP_CACHE_MASTER_KEY")?;
    /// let cache = cachekit::CacheKit::secure("redis://localhost:6379", &master_key_hex)
    ///     .await?
    ///     .build()?;
    /// let secure = cache.secure_cache()?;
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(all(feature = "redis", feature = "encryption"))]
    pub async fn secure(
        redis_url: &str,
        master_key_hex: &str,
    ) -> Result<CacheKitBuilder, CachekitError> {
        let master_key = crate::config::decode_master_key_hex(master_key_hex, "master_key_hex")?;
        connect_secure(redis_url, secure_defaults(&master_key, &[])?).await
    }

    /// **Secure**, keys from the environment — [`CacheKit::secure`] with the
    /// hex key read from `CACHEKIT_MASTER_KEY`, plus decrypt-only rotation
    /// keys from `CACHEKIT_PREVIOUS_MASTER_KEYS`.
    ///
    /// Reads exactly two variables:
    ///
    /// * `CACHEKIT_MASTER_KEY` (required) — the current key; writes encrypt
    ///   under it. Same hex decoding as [`secure`](CacheKit::secure), so the
    ///   same value derives the same key bytes as every other CacheKit SDK.
    ///   Use exactly **32 bytes (64 hex chars)**, the only length every SDK
    ///   accepts.
    /// * `CACHEKIT_PREVIOUS_MASTER_KEYS` (optional) — comma-separated hex
    ///   keys, at most 3, tried in order when the current key fails to
    ///   decrypt. Unset or blank means none. Validated exactly as
    ///   [`CachekitConfig::from_env`](crate::CachekitConfig::from_env)
    ///   validates it; the current key must not appear in the list.
    ///
    /// Otherwise the identical preset to [`secure`](CacheKit::secure), tenant
    /// `"default"` for every key. Never falls back to plaintext.
    ///
    /// # Errors
    ///
    /// Returns [`CachekitError::Config`] — all before any Redis I/O — when
    /// `CACHEKIT_MASTER_KEY` is unset, empty, not hex, or shorter than 32
    /// bytes, or when `CACHEKIT_PREVIOUS_MASTER_KEYS` is set but not valid
    /// UTF-8, or is non-blank with an empty or invalid entry, more than 3
    /// entries, or a repeat of the current key.
    /// Otherwise as [`secure`](CacheKit::secure).
    ///
    /// # Example
    ///
    /// ```no_run
    /// # async fn example() -> Result<(), cachekit::CachekitError> {
    /// let cache = cachekit::CacheKit::secure_from_env("redis://localhost:6379")
    ///     .await?
    ///     .build()?;
    /// let secure = cache.secure_cache()?;
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(all(feature = "redis", feature = "encryption"))]
    pub async fn secure_from_env(redis_url: &str) -> Result<CacheKitBuilder, CachekitError> {
        connect_secure(redis_url, secure_env_defaults()?).await
    }

    /// **CachekitIO** — managed SaaS cache, zero infrastructure.
    ///
    /// * Backend: [cachekit.io](https://cachekit.io) HTTP API
    /// * L1 cache: **on** (1 000 entries)
    /// * Encryption: **no** (add via
    ///   [`.encryption()`](CacheKitBuilder::encryption))
    /// * Reliability: **on** — retry with backoff + jitter, circuit
    ///   breaker, backpressure (max 100 concurrent backend ops)
    /// * Default TTL: **3 600 s**
    ///
    /// Good for: serverless, edge compute, managed caching without Redis.
    ///
    /// Use [`CacheKit::io_from_env`] to read the key from `CACHEKIT_API_KEY`.
    ///
    /// # Errors
    ///
    /// Returns [`CachekitError::Config`] if `api_key` is empty.
    ///
    /// # Example
    ///
    /// ```no_run
    /// # fn example() -> Result<(), Box<dyn std::error::Error>> {
    /// let api_key = std::env::var("CACHEKIT_API_KEY")?;
    /// let cache = cachekit::CacheKit::io(&api_key)?
    ///     .namespace("edge")
    ///     .build()?;
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(all(feature = "cachekitio", not(target_arch = "wasm32")))]
    pub fn io(api_key: &str) -> Result<CacheKitBuilder, CachekitError> {
        let backend = crate::backend::cachekitio::CachekitIO::builder()
            .api_key(api_key)
            .build()?;

        let builder = CacheKitBuilder::default()
            .backend(wrap(backend))
            .default_ttl(Duration::from_secs(3600))
            .l1_capacity(1000);
        #[cfg(all(feature = "reliability", not(target_arch = "wasm32")))]
        let builder = builder.reliability(crate::reliability::ReliabilityConfig::default());
        Ok(builder)
    }

    /// **CachekitIO**, API key from the environment — [`CacheKit::io`] with
    /// the key read from `CACHEKIT_API_KEY`.
    ///
    /// Identical preset to [`io`](CacheKit::io). Reads **only**
    /// `CACHEKIT_API_KEY` — unlike [`CacheKit::from_env`], never
    /// `CACHEKIT_MASTER_KEY`, so no encryption is activated.
    ///
    /// # Errors
    ///
    /// Returns [`CachekitError::Config`] when `CACHEKIT_API_KEY` is unset or
    /// empty.
    ///
    /// # Example
    ///
    /// ```no_run
    /// # fn example() -> Result<(), cachekit::CachekitError> {
    /// let cache = cachekit::CacheKit::io_from_env()?
    ///     .namespace("edge")
    ///     .build()?;
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(all(feature = "cachekitio", not(target_arch = "wasm32")))]
    pub fn io_from_env() -> Result<CacheKitBuilder, CachekitError> {
        let api_key = std::env::var("CACHEKIT_API_KEY")
            .ok()
            .map(zeroize::Zeroizing::new)
            .filter(|k| !k.is_empty())
            .ok_or_else(|| {
                CachekitError::Config(
                    "CACHEKIT_API_KEY is unset or empty: set it or pass the key to CacheKit::io(api_key)"
                        .to_owned(),
                )
            })?;
        Self::io(&api_key)
    }
}

#[cfg(all(test, feature = "redis", feature = "l1"))]
#[allow(clippy::expect_used)] // test-only: a failing build here should panic loudly
mod tests {
    /// `RedisBackend::build()` does not connect, so the preset's defaults
    /// are observable without a live server.
    #[test]
    fn minimal_enables_l1_without_swr() {
        let backend = crate::backend::redis::RedisBackend::builder()
            .url("redis://localhost:6379")
            .build()
            .expect("valid URL");
        let cache = super::minimal_defaults(super::wrap(backend))
            .build()
            .expect("minimal defaults must build");

        assert!(
            cache.l1.is_some(),
            "spec/intent-presets.md § L1 Posture: minimal MUST enable L1"
        );
        #[cfg(all(not(feature = "unsync"), not(target_arch = "wasm32")))]
        assert!(
            !cache.swr_enabled,
            "spec/intent-presets.md § L1 Posture: minimal MUST NOT enable SWR"
        );
    }
}

#[cfg(all(test, feature = "redis", feature = "encryption"))]
#[allow(clippy::expect_used)] // test-only: a failing build here should panic loudly
mod secure_tests {
    // protocol test-vectors/encryption.json v1.2.0, `default_tenant.vectors[0]`
    // (`default_tenant_interop`): spec/intent-presets.md § Master Key Input
    // rule 5 — with no tenant configured, the preset must derive and bind AAD
    // under the literal "default", byte-for-byte with every other SDK.
    const MASTER_KEY_HEX: &str = "6161616161616161616161616161616161616161616161616161616161616161";
    const CACHE_KEY: &str =
        "users:get_user:61598716255080080f6456eb065c2e51badfaa4320b0efe97469c29cffee8875";
    const CIPHERTEXT_HEX: &str =
        "0d0e0f1011121314151617183c29af318238925ee76d081934adce133c0b4a7c5eb5704102b04582dcbf278ffd"; // pragma: allowlist secret
    const PLAINTEXT_HEX: &str = "82a36167651ea46e616d65a5616c696365"; // pragma: allowlist secret

    fn assert_decrypts_default_tenant_vector(builder: crate::CacheKitBuilder) {
        let layer = builder
            .encryption
            .expect("secure preset must configure encryption");
        assert_eq!(layer.tenant_id(), "default");
        let ciphertext = hex::decode(CIPHERTEXT_HEX).expect("vector hex");
        let plaintext = layer
            .decrypt(&ciphertext, CACHE_KEY)
            .expect("default-tenant vector must decrypt");
        assert_eq!(hex::encode(plaintext), PLAINTEXT_HEX);
    }

    #[test]
    fn hex_path_decrypts_default_tenant_vector() {
        assert_decrypts_default_tenant_vector(
            super::secure_defaults(&hex::decode(MASTER_KEY_HEX).expect("vector hex"), &[])
                .expect("valid key"),
        );
    }

    /// Rule 3: the hex path accepts a key decoding to more than 32 bytes;
    /// the raw-bytes exactly-32 rule must not leak into it.
    #[test]
    fn hex_path_accepts_48_byte_key() {
        let long = [0x61u8; 48];
        assert!(super::secure_defaults(&long, &[]).is_ok());
        let previous = [zeroize::Zeroizing::new(vec![0x62u8; 48])];
        assert!(super::secure_defaults(&long, &previous).is_ok());
    }

    #[test]
    #[serial_test::serial]
    fn env_path_accepts_48_byte_keys() {
        let (k2, k1) = ("22".repeat(48), "11".repeat(48));
        assert!(secure_env_defaults_with(Some(&k2), Some(&k1)).is_ok());
        assert!(secure_env_defaults_with(Some(&"22".repeat(32)), None).is_ok());
    }

    /// Run `secure_env_defaults` under the given env, restoring both
    /// variables before anything can panic.
    fn secure_env_defaults_with(
        master: Option<&str>,
        previous: Option<&str>,
    ) -> Result<crate::CacheKitBuilder, crate::CachekitError> {
        const VARS: [&str; 2] = ["CACHEKIT_MASTER_KEY", "CACHEKIT_PREVIOUS_MASTER_KEYS"];
        let saved = VARS.map(std::env::var_os);
        for (var, val) in VARS.iter().zip([master, previous]) {
            match val {
                Some(v) => std::env::set_var(var, v),
                None => std::env::remove_var(var),
            }
        }
        let resolved = super::secure_env_defaults();
        for (var, val) in VARS.iter().zip(saved) {
            match val {
                Some(v) => std::env::set_var(var, v),
                None => std::env::remove_var(var),
            }
        }
        resolved
    }

    #[test]
    #[serial_test::serial]
    fn env_path_decrypts_default_tenant_vector() {
        assert_decrypts_default_tenant_vector(
            secure_env_defaults_with(Some(MASTER_KEY_HEX), None).expect("valid key"),
        );
    }

    /// LAB-6591: an entry written under k1 must still decrypt after the
    /// env-var rotation runbook promotes k2 and moves k1 to the previous list.
    #[test]
    #[serial_test::serial]
    fn env_path_decrypts_under_previous_key_after_rotation() {
        let k2 = "22".repeat(32);
        let rotated = secure_env_defaults_with(Some(&k2), Some(MASTER_KEY_HEX))
            .expect("valid rotation config");
        // The default-tenant vector was written under k1 (MASTER_KEY_HEX).
        assert_decrypts_default_tenant_vector(rotated);

        // Control: without the previous key, k2 alone fails closed.
        let layer = secure_env_defaults_with(Some(&k2), None)
            .expect("valid key")
            .encryption
            .expect("secure preset must configure encryption");
        let ciphertext = hex::decode(CIPHERTEXT_HEX).expect("vector hex");
        assert!(layer.decrypt(&ciphertext, CACHE_KEY).is_err());
    }

    #[test]
    #[serial_test::serial]
    fn env_path_blank_previous_keys_is_unset() {
        assert_decrypts_default_tenant_vector(
            secure_env_defaults_with(Some(MASTER_KEY_HEX), Some("  ")).expect("blank is unset"),
        );
    }

    /// Set but unreadable is not unset: a non-UTF-8 value must fail, never
    /// silently drop the decrypt-only keys.
    #[cfg(unix)]
    #[test]
    #[serial_test::serial]
    fn env_path_rejects_non_utf8_previous_keys() {
        use std::os::unix::ffi::OsStringExt;
        let saved = std::env::var_os("CACHEKIT_PREVIOUS_MASTER_KEYS");
        std::env::set_var(
            "CACHEKIT_PREVIOUS_MASTER_KEYS",
            std::ffi::OsString::from_vec(vec![0x31, 0xff, 0x31]),
        );
        let saved_master = std::env::var_os("CACHEKIT_MASTER_KEY");
        std::env::set_var("CACHEKIT_MASTER_KEY", MASTER_KEY_HEX);
        let resolved = super::secure_env_defaults();
        for (var, val) in [
            ("CACHEKIT_PREVIOUS_MASTER_KEYS", saved),
            ("CACHEKIT_MASTER_KEY", saved_master),
        ] {
            match val {
                Some(v) => std::env::set_var(var, v),
                None => std::env::remove_var(var),
            }
        }
        assert!(
            matches!(
                &resolved,
                Err(crate::CachekitError::Config(msg)) if msg.contains("CACHEKIT_PREVIOUS_MASTER_KEYS")
            ),
            "non-UTF-8 previous keys must be a Config error naming the variable; got {:?}",
            resolved.err()
        );
    }

    #[test]
    #[serial_test::serial]
    fn env_path_rejects_invalid_previous_keys() {
        let k2 = "22".repeat(32);
        let four = ["11", "33", "44", "55"].map(|b| b.repeat(32)).join(",");
        for (previous, why) in [
            ("not-hex", "invalid hex"),
            (&*format!("{MASTER_KEY_HEX},"), "empty entry"),
            (&*"11".repeat(31), "short key"),
            (&*four, "more than 3"),
            (&*k2, "current key repeated"),
        ] {
            assert!(
                matches!(
                    secure_env_defaults_with(Some(&k2), Some(previous)),
                    Err(crate::CachekitError::Config(_))
                ),
                "{why} must be a Config error"
            );
        }
    }
}