makeover-layout 0.45.0

//! The crate's own tests, in the file the crate's `mod tests;` names.
//!
//! Moved out of `lib.rs` whole: the root is a facade of `pub use` lines, and
//! 2,000 lines of tests under 250 lines of re-exports made the facade the
//! smaller half of the file that declares it.

use super::{Change, Intent as _, Syntax};

/// Every name a caller is told to use, reached through the root path.
///
/// The thirteen modules are private, so a member left out of the facade
/// stays reachable inside the crate and vanishes from the API outside it,
/// which is a silent semver break. This is where that fails instead.
#[test]
fn the_names_a_caller_is_told_to_use_are_exported_from_the_root() {
    #[allow(unused_imports)]
    use crate::{
        Accepted, Act, Arrangement, Awaiting, Bevel, Candidate, CellPart, Change, Choice, Column,
        Contrast, Curve, DATE_FORMAT, DATETIME_FORMAT, Depth, Edge, Extent, Facet, FacetValue,
        Fallback, Family, Field, FieldKind, Figure, Fill, Fit, Flow, Heading, Intent, Loading,
        Measure, Meter, Nesting, Notice, Paging, Placement, Priority, Readiness, Region, RowPart,
        Selecting, Selector, Share, Showing, Sort, Span, Standing, State, Syntax, ThemeChoice,
        ThemeVariant, Token, Tone, Track, Unit, Width, Window,
    };
}

/// A run nothing claimed is a real answer rather than a missing one, which
/// is why this is not an `Option<Syntax>`: a lexer that ran and found
/// ordinary code has said something.
#[test]
fn an_unclassified_run_is_plain_and_plain_is_the_default() {
    assert_eq!(Syntax::default(), Syntax::Plain);
    assert_eq!(Syntax::Plain.name(), "plain");
}

/// Every class has a stable lowercase name, and no two share one. The
/// spelling is named here rather than agreed per renderer, which is what
/// stops one calling it `str` and the next `string`.
#[test]
fn every_syntax_class_has_its_own_spelling() {
    let all = [
        Syntax::Plain,
        Syntax::Keyword,
        Syntax::String,
        Syntax::Comment,
        Syntax::Constant,
        Syntax::Entity,
        Syntax::Variable,
        Syntax::Support,
    ];
    let mut seen = std::collections::BTreeSet::new();
    for class in all {
        assert!(!class.name().is_empty(), "{class:?} has no spelling");
        assert!(seen.insert(class.name()), "{class:?} shares a spelling");
    }
    assert_eq!(seen.len(), all.len());
}

/// Context is a state and not an absence, so an unchanged line is
/// distinguishable from a line nobody marked. `Syntax::Plain`'s argument.
#[test]
fn an_unmarked_diff_line_is_context() {
    assert_eq!(Change::default(), Change::Context);
    assert_eq!(Change::Context.token(), "content");
}

/// The two sides reuse the status axis rather than minting a palette. An
/// app holding them fixed across themes says so in its own sheet.
#[test]
fn the_two_sides_of_a_change_take_the_status_intents() {
    assert_eq!(Change::Added.token(), "success");
    assert_eq!(Change::Removed.token(), "danger");
}

/// The concept is named here and its magnitude is not, which is
/// `Awaiting`'s split and is why a renderer can disagree with another
/// about what a level is worth without either of them being wrong.
#[test]
fn nesting_says_how_deep_and_not_how_wide() {
    assert_eq!(Nesting::default(), Nesting::top());
    assert_eq!(Nesting::top().level, 0);
    assert!(!Nesting::top().is_nested());

    let under = Nesting::at(2);
    assert_eq!(under.level, 2);
    assert!(under.is_nested());

    // Ordered, so a renderer walking a flat list of rows can compare two
    // levels rather than reaching into the field.
    assert!(Nesting::top() < under);
}

use super::*;

#[test]
fn a_markdown_field_is_multiline_and_offers_nothing() {
    // The editing counterpart of markdown prose is still text: every host
    // can draw it, which is the whole reason the kind was addable.
    assert!(FieldKind::Rich.multiline());
    assert!(FieldKind::Textarea.multiline());
    assert!(!FieldKind::Text.multiline());
    // It is not a chooser and not a moment.
    assert!(!FieldKind::Rich.offers_options());
    assert!(!FieldKind::Rich.temporal());
    assert!(FieldKind::Rich.visible());
}

#[test]
fn only_the_numeric_kinds_are_measurable() {
    assert!(FieldKind::Number.measurable());
    assert!(FieldKind::Range.measurable());
    // An axis is measured in something and both its ends are in it, so the
    // unit is read once for the pair rather than per end.
    assert!(FieldKind::Interval.measurable());
    // A date is ordered and is not a quantity with a unit to choose: its
    // unit is fixed by the kind, so saying one would restate `kind`.
    for kind in [
        FieldKind::Text,
        FieldKind::Date,
        FieldKind::DateTime,
        FieldKind::Select,
        FieldKind::Checkbox,
        FieldKind::File,
    ] {
        assert!(!kind.measurable(), "{kind:?}");
    }
}

#[test]
fn a_field_carries_no_unit_until_one_is_given() {
    // Additive: absent is what every field described before 0.33.0 meant.
    let plain = Field::new(FieldKind::Number, "attack", "Attack");
    assert_eq!(plain.unit, None);
    let measured = Field {
        unit: Some("s"),
        ..Field::range("attack", "Attack", "0.001", "5")
    };
    assert_eq!(measured.unit, Some("s"));
    assert!(measured.kind.measurable());
}

#[test]
fn an_interval_states_both_ends_names() {
    // Stated rather than derived: the two measured sites disagree about
    // affix order, so a rule here would rename one of them.
    let suffixed = Field::interval("bpm_min", "bpm_max", "BPM");
    assert_eq!(suffixed.name, "bpm_min");
    assert_eq!(suffixed.upper_name, Some("bpm_max"));
    let prefixed = Field::interval("min_price", "max_price", "Price");
    assert_eq!(prefixed.name, "min_price");
    assert_eq!(prefixed.upper_name, Some("max_price"));
    assert_eq!(suffixed.kind, FieldKind::Interval);
}

#[test]
fn every_other_kind_has_no_upper_end() {
    // Additive: absent is what every field described before 0.34.0 meant.
    for kind in [FieldKind::Text, FieldKind::Number, FieldKind::Range] {
        assert_eq!(Field::new(kind, "n", "N").upper_name, None, "{kind:?}");
    }
    assert_eq!(Field::range("t", "T", "0", "1").upper_name, None);
}

#[test]
fn an_interval_owes_no_bounds_and_takes_the_axis_facts_once() {
    // A range's bounds are the control's extent and are owed; an interval's
    // are a rule on each end, which is Number's arrangement.
    let plain = Field::interval("bpm_min", "bpm_max", "BPM");
    assert!(!plain.bounded());
    let axis = Field {
        min: Some("0"),
        max: Some("300"),
        step: Some("1"),
        unit: Some("BPM"),
        ..Field::interval("bpm_min", "bpm_max", "BPM")
    };
    assert!(axis.bounded());
    assert_eq!(axis.unit, Some("BPM"));
    // Nothing here checks the crossing rule, exactly as nothing checks
    // `min` for a number: the description carries constraints and whoever
    // validated decides a value is wrong.
    assert!(axis.error.is_none());
}

#[test]
fn only_a_subtree_prunes_and_only_the_listing_modes_offer_values() {
    // Excluding a value from a flat facet is the same fact as not picking
    // it, so the affordance exists in exactly one mode.
    assert!(Selecting::Subtree.prunes());
    for mode in [
        Selecting::OneOf,
        Selecting::AnyOf,
        Selecting::Range,
        Selecting::Text,
    ] {
        assert!(!mode.prunes(), "{mode:?}");
    }
    // Text and Range answer with something that is not one of a set.
    assert!(!Selecting::Text.offers_values());
    assert!(!Selecting::Range.offers_values());
    assert!(Selecting::OneOf.offers_values());
    assert!(Selecting::AnyOf.accumulates());
    assert!(!Selecting::OneOf.accumulates());
}

#[test]
fn an_inherited_value_is_in_force_without_having_been_picked() {
    // The distinction a bool cannot hold, and the reason Standing has four
    // members: a child under a taken parent narrows the set, and clearing
    // it clears nothing.
    assert!(Standing::Inherited.in_force());
    assert!(!Standing::Inherited.is_picked());
    assert!(Standing::Taken.in_force());
    assert!(Standing::Taken.is_picked());
    // A prune is a decision that takes the value out.
    assert!(Standing::Pruned.is_picked());
    assert!(!Standing::Pruned.in_force());
    assert!(!Standing::Open.is_picked());
    assert!(!Standing::Open.in_force());
    // A pruned branch still answers a press, so it may not read as inert.
    assert_ne!(Standing::Pruned.intent(), "content-muted");
}

#[test]
fn a_facet_is_engaged_by_a_decision_and_not_by_an_inherited_value() {
    let inherited = [
        FacetValue::of("music")
            .standing(Standing::Taken)
            .at(Nesting::at(0), true),
        FacetValue::new("music/synths", "synths")
            .standing(Standing::Inherited)
            .at(Nesting::at(1), false),
    ];
    let facet = Facet::new("Tag", Selecting::Subtree, &inherited);
    assert!(facet.engaged());
    // The gutter an indenting renderer reserves before its first paint.
    assert_eq!(facet.reach(), 1);

    let untouched = [
        FacetValue::of("music").at(Nesting::at(0), true),
        FacetValue::new("music/synths", "synths")
            .standing(Standing::Inherited)
            .at(Nesting::at(1), false),
    ];
    // Inherited alone is something further up doing the narrowing, and
    // there is nothing further up here.
    assert!(!Facet::new("Tag", Selecting::Subtree, &untouched).engaged());

    // A text facet lists nothing, so it is flat and never reads as engaged
    // from its values: the typed string is not held here.
    let typed = Facet::new("Search", Selecting::Text, &[]);
    assert!(!typed.engaged());
    assert_eq!(typed.reach(), 0);
}

#[test]
fn a_count_is_absent_rather_than_zero_when_it_was_not_measured() {
    // Awaiting::amount's rule in a second place: a written zero reads as
    // "none of them", which is a different claim from "not counted".
    assert_eq!(FacetValue::of("Ambient").count, None);
    assert_eq!(FacetValue::of("Ambient").counted(0).count, Some(0));
}

#[test]
fn one_kind_takes_files_and_the_two_file_members_are_its_alone() {
    assert!(FieldKind::File.takes_files());
    for kind in [
        FieldKind::Text,
        FieldKind::Textarea,
        FieldKind::Rich,
        FieldKind::Select,
        FieldKind::Checkbox,
        FieldKind::Hidden,
    ] {
        assert!(!kind.takes_files());
    }
    // The default is a field that takes any one file, which is what an
    // input with no accept and no multiple already is.
    let plain = Field::new(FieldKind::File, "cover", "Cover");
    assert!(plain.accept.is_empty());
    assert!(!plain.multiple);
}

#[test]
fn an_accept_list_says_which_disclosure_and_a_suffix_says_none() {
    // The three shapes are the MNW server's own three, and the family is
    // the question a renderer asks before it keeps room for a preview.
    assert_eq!(
        Accepted::Family(Family::Image).family(),
        Some(Family::Image)
    );
    assert_eq!(Accepted::Type("image/jpeg").family(), Some(Family::Image));
    assert_eq!(Accepted::Type("audio/flac").family(), Some(Family::Audio));
    assert_eq!(
        Accepted::Type("video/quicktime").family(),
        Some(Family::Video)
    );
    // A media type outside the three families names none, and neither does
    // a suffix. `.mp3` is audio in fact and this crate will not infer it:
    // the table that said so would rot.
    assert_eq!(Accepted::Type("text/csv").family(), None);
    assert_eq!(Accepted::Suffix(".mp3").family(), None);
    assert_eq!(Accepted::Suffix(".tar.gz").family(), None);
    // Media types are case-insensitive and half the tree writes them
    // lowercase by habit rather than by rule.
    assert_eq!(Accepted::Type("IMAGE/PNG").family(), Some(Family::Image));
}

#[test]
fn every_accepted_entry_has_one_spelling_a_host_can_write() {
    assert_eq!(Accepted::Family(Family::Image).as_str(), "image/*");
    assert_eq!(Accepted::Family(Family::Audio).as_str(), "audio/*");
    assert_eq!(Accepted::Family(Family::Video).as_str(), "video/*");
    assert_eq!(Accepted::Type("text/csv").as_str(), "text/csv");
    assert_eq!(Accepted::Suffix(".tar.gz").as_str(), ".tar.gz");
}

#[test]
fn a_list_accepting_two_families_still_has_a_disclosure_to_offer() {
    // The measured dropzone: `accept="image/*,video/*"`. There is no single
    // family to return and there is still a preview to keep room for, which
    // is why the question is asked of the list rather than of one entry.
    const MEDIA: &[Accepted<'_>] = &[
        Accepted::Family(Family::Image),
        Accepted::Family(Family::Video),
    ];
    assert!(Field::upload("media", "Media", MEDIA).accepts_media());
    // An installer's suffix list wants no disclosure, which is the measured
    // case rather than a hypothetical one.
    const BUILDS: &[Accepted<'_>] = &[Accepted::Suffix(".zip"), Accepted::Suffix(".dmg")];
    assert!(!Field::upload("build", "Build", BUILDS).accepts_media());
    // And a field that takes anything says so by listing nothing.
    assert!(!Field::upload("any", "File", &[]).accepts_media());
}

#[test]
fn an_upload_carries_its_list_and_takes_one_file_until_it_says_otherwise() {
    const IMAGES: &[Accepted<'_>] = &[
        Accepted::Type("image/jpeg"),
        Accepted::Type("image/png"),
        Accepted::Type("image/webp"),
    ];
    let avatar = Field::upload("avatar", "Avatar", IMAGES);
    assert_eq!(avatar.kind, FieldKind::File);
    assert_eq!(avatar.accept, IMAGES);
    assert!(!avatar.multiple);
    let several = Field {
        multiple: true,
        ..avatar
    };
    assert!(several.multiple);
}

#[test]
fn the_four_readiness_states_are_one_axis_and_only_one_shows_content() {
    // Mutually exclusive is the test for one enum against several fields: a
    // region shows its content, or that it is coming, or that there is none,
    // or that it broke. Never two.
    assert!(Readiness::Ready.shows_content());
    for state in [Readiness::Pending, Readiness::Empty, Readiness::Failed] {
        assert!(!state.shows_content());
    }
}

#[test]
fn a_region_shows_all_of_its_children_unless_it_says_otherwise() {
    // The default is the behaviour every region had before this member
    // existed, which is what keeps it additive: a description written
    // against 0.22.0 says the same thing under 0.23.0.
    assert_eq!(Showing::default(), Showing::All);
    assert!(!Showing::All.selective());
}

#[test]
fn only_a_disclosure_can_show_nothing() {
    // The two derived idioms differ in one respect and this is it. A
    // carousel's row moves between frames and never reaches empty; a
    // disclosure's summary line is the same control wearing its closed
    // state, so a renderer has to know which it is drawing.
    assert!(Showing::AtMostOne.dismissible());
    assert!(!Showing::One.dismissible());
    assert!(!Showing::All.dismissible());

    // Both are selective, though. Deriving chrome is one question and
    // whether that chrome closes is another.
    assert!(Showing::One.selective());
    assert!(Showing::AtMostOne.selective());
}

#[test]
fn an_empty_region_is_not_a_broken_one() {
    // An empty list is the normal state of a new install. Drawing it in a
    // danger tone reports a fault where there is none, and this is the one
    // place the distinction is carried.
    assert_eq!(Readiness::Empty.tone(), Tone::Neutral);
    assert_eq!(Readiness::Failed.tone(), Tone::Danger);
    assert_eq!(Readiness::Pending.tone(), Tone::Neutral);
}

#[test]
fn a_column_can_be_sorted_without_being_sortable() {
    // Both combinations mean something, which is why the two fields are
    // independent rather than one implying the other. A list ordered by a
    // key the user cannot change is a real thing with a caret worth drawing.
    let fixed = Column {
        sorted: Some(Sort::Descending),
        ..Column::new("Created")
    };

    assert!(!fixed.sortable);
    assert_eq!(fixed.sorted.map(Sort::as_str), Some("descending"));

    let offered = Column {
        sortable: true,
        ..Column::new("Name")
    };
    assert_eq!(offered.sorted, None);
}

#[test]
fn a_direction_flips_and_says_what_it_is() {
    assert_eq!(Sort::Ascending.reversed(), Sort::Descending);
    assert_eq!(Sort::Descending.reversed().reversed(), Sort::Descending);
    assert_eq!(Sort::Ascending.as_str(), "ascending");
}

#[test]
fn a_direction_carries_its_caret_and_the_two_are_not_the_same_glyph() {
    // The spelling every renderer reads, so that agreeing is composition
    // rather than three files happening to hold the same literal.
    assert_eq!(Sort::Ascending.glyph(), "\u{25B2}");
    assert_eq!(Sort::Descending.glyph(), "\u{25BC}");
    assert_ne!(Sort::Ascending.glyph(), Sort::Descending.glyph());
    // Bare. The gap is the renderer's, and a space here would be a second
    // one wherever a renderer already carries its own.
    for d in [Sort::Ascending, Sort::Descending] {
        assert_eq!(d.glyph().trim(), d.glyph());
    }
}

#[test]
fn a_figure_carries_its_tone_because_no_renderer_can_derive_it() {
    // Three of goingson's five sites tone the figure by their own means, so
    // tone is carried at every site that needs it and derived at none. The
    // same reasoning `Meter` reached, from a different direction.
    let streak = Figure::new("0", "Current Streak").tone(Tone::Warning);
    assert_eq!(streak.tone, Tone::Warning);
    assert_eq!(Figure::new("17", "Total").tone, Tone::Neutral);
}

#[test]
fn a_figures_change_is_the_toned_part_and_is_absent_by_default() {
    // 0.13.0. The MNW server's stat card is a label, a value and a delta,
    // across four screens, and the delta is what reads as good or bad. Tone
    // had no consumer before this: the figure itself is an ordinary fact.
    let views = Figure::new("1,204", "Views")
        .change("+12.5%")
        .tone(Tone::Success);
    assert_eq!(views.change, Some("+12.5%"));
    assert_eq!(views.tone, Tone::Success);

    // A figure with nothing to compare against says so by having no change,
    // rather than by carrying an empty string a renderer has to test for.
    assert_eq!(Figure::new("3.1%", "Conversion").change, None);
}

#[test]
fn a_figures_value_is_text_because_only_the_app_knows_what_it_is() {
    // "84%", "12/30", "3d". A figure is whatever the app computed, already
    // formatted, and that is the line between this and `Meter`: a meter is
    // a proportion a renderer draws, a figure is a fact it sets in type.
    for value in ["84%", "12/30", "3d"] {
        assert_eq!(Figure::new(value, "Rate").value, value);
    }
}

#[test]
fn a_proportion_is_a_row_part_and_takes_no_intent_of_its_own() {
    // The meter carries the tone, so a part-level intent underneath would
    // fight it. Same answer `Tokens` needed, for the same reason.
    assert_eq!(RowPart::Proportion.intent(), RowPart::Tokens.intent());
}

#[test]
fn a_file_field_is_drawn_and_offers_no_options() {
    // It is a control the user operates, unlike `Hidden`, and it does not
    // pick from a list the description carries, unlike `Select`.
    assert!(FieldKind::File.visible());
    assert!(!FieldKind::File.offers_options());
    assert!(!FieldKind::File.confidential());
}

#[test]
fn a_constraint_is_a_fact_about_the_question_and_not_a_verdict() {
    // The whole model: the description carries the rule, the renderer emits
    // its host's idiom, and `error` is what arrives back when someone
    // validated. Nothing here decides a value is wrong.
    let field = Field {
        max_length: Some(100),
        min: Some("1"),
        max: Some("240"),
        required: true,
        ..Field::new(FieldKind::Number, "minutes", "Minutes")
    };
    assert!(!field.invalid());

    // A bound is text because it is only a number for some of the kinds
    // that take one. goingson has both shapes live.
    let when = Field {
        min: Some("2026-08-09T14:30"),
        ..Field::new(FieldKind::Text, "starts", "Starts")
    };
    assert_eq!(when.min, Some("2026-08-09T14:30"));
}

#[test]
fn a_meter_keeps_the_over_run_the_percentage_throws_away() {
    // The whole reason this is a pair. goingson's `Task::time_progress`
    // clamps to 100 and then carries `is_over_estimate` beside it to say
    // what the clamp dropped; a meter says both from one fact.
    let over = Meter::new(45, 30);
    assert_eq!(over.percent(), 100);
    assert!(over.overflowing());

    let exact = Meter::new(30, 30);
    assert_eq!(exact.percent(), over.percent());
    assert!(!exact.overflowing());
}

#[test]
fn an_empty_set_does_not_divide_by_zero() {
    // Sayable on purpose, so it has to be answerable. A meter over an
    // unloaded count is what an app actually has for a frame.
    let none = Meter::new(0, 0);
    assert_eq!(none.percent(), 0);
    assert!(none.is_empty());
    assert!(!none.overflowing());
}

#[test]
fn the_ratio_survives_where_a_percentage_would_not() {
    // Given 43 nothing can recover "3 of 7", which is why the numbers are
    // carried and the label names only the noun.
    let m = Meter::new(3, 7).label("subtasks");
    assert_eq!(m.percent(), 42);
    assert_eq!((m.done, m.total), (3, 7));
    assert_eq!(m.label, Some("subtasks"));
}

#[test]
fn tone_is_carried_because_no_renderer_can_derive_it() {
    // The same fullness means opposite things on two of goingson's bars,
    // and only the app knows which.
    let subtasks = Meter::new(9, 10).tone(Tone::Success);
    let estimate = Meter::new(9, 10).tone(Tone::Danger);
    assert_eq!(subtasks.percent(), estimate.percent());
    assert_ne!(subtasks.tone, estimate.tone);
    // Untoned by default: a bar says nothing about status until something
    // says so, the same way a row is not selectable until told.
    assert_eq!(Meter::new(9, 10).tone, Tone::Neutral);
}

#[test]
fn an_act_is_reachable_until_it_is_disabled() {
    // The one member a renderer must branch on, and since 0.19.0 the only
    // member there is. A stated state is not by itself a reason to stop
    // answering, which is the distinction `State` makes and every
    // hand-rolled button in the tree had to remember.
    assert!(!Act::new("Save").disabled());
    assert!(Act::new("Save").state(State::Disabled).disabled());
}

#[test]
fn an_act_carries_its_key_because_a_terminal_has_nothing_else() {
    // No key is the ordinary case, and the webview hosts that ignore it
    // are why it stayed optional.
    assert_eq!(Act::new("Delete").key, None);
    let quit = Act::new("Quit").key("q").tone(Tone::Danger);
    assert_eq!(quit.key, Some("q"));
    assert_eq!(quit.tone, Tone::Danger);
}

#[test]
fn a_meter_does_not_overflow_on_large_counts() {
    // done * 100 in u32 would wrap somewhere past 42 million. Counts that
    // size are not tasks, but a description layer that silently reports 3%
    // for a full bar is worse than one that is slow.
    let big = Meter::new(u32::MAX, u32::MAX);
    assert_eq!(big.percent(), 100);
    assert!(!big.overflowing());
}

#[test]
fn inset_is_raised_with_the_light_moved() {
    let (rl, rd) = Bevel::Raised.edges();
    let (il, id) = Bevel::Inset.edges();
    assert_eq!((rl, rd), (Edge::Light, Edge::Dark));
    assert_eq!((il, id), (rd, rl));
}

#[test]
fn pressing_twice_is_a_no_op() {
    for b in [Bevel::Raised, Bevel::Inset] {
        assert_eq!(b.pressed().pressed(), b);
    }
}

#[test]
fn a_raised_region_is_never_filled_with_a_recessed_surface() {
    // The bug this vocabulary exists to make unrepresentable.
    assert_eq!(Depth::Raised.fill(), Some(Fill::Raised));
    assert_eq!(Depth::Raised.bevel(), Some(Bevel::Raised));
    assert_eq!(Depth::Well.bevel(), Some(Bevel::Inset));
    assert_ne!(Depth::Well.fill(), Depth::Raised.fill());
}

#[test]
fn state_is_orthogonal_to_depth() {
    // The reason State is its own axis and not a Depth member: a disabled
    // button and a disabled field are both disabled and are not the same
    // shape, which one shared variant could not have said.
    assert_eq!(Depth::Raised.fill(), Some(Fill::Raised));
    assert_eq!(Depth::Well.fill(), Some(Fill::Well));
    assert!(State::Disabled.suppresses_interaction());
}

#[test]
fn only_disabled_stops_answering() {
    // Kept in spirit from the version where `Focus` was the counter-example:
    // suppressing interaction is `Disabled`'s alone, so a member added here
    // later does not get to inherit it by being a state.
    assert!(State::Disabled.suppresses_interaction());
}

#[test]
fn disabled_resolves_against_an_intent_makeover_already_derives() {
    // No new token, so this costs no `makeover` release.
    assert_eq!(State::Disabled.token(), "content-muted");
}

#[test]
fn flat_has_neither_edge_nor_fill() {
    assert_eq!(Depth::Flat.bevel(), None);
    assert_eq!(Depth::Flat.fill(), None);
}

#[test]
fn sunken_is_recessed_by_colour_with_no_edge() {
    // The one member carrying a fill without a bevel. A renderer that
    // assumes the two arrive together drops the fill silently, which is
    // exactly what makeover-webview did before 0.3.0.
    assert_eq!(Depth::Sunken.fill(), Some(Fill::Sunken));
    assert_eq!(Depth::Sunken.bevel(), None);
}

#[test]
fn sunken_and_flat_are_different_claims() {
    // Both edgeless, and only one of them needs a colour. Collapsing them
    // is what left an unchosen tab unsayable.
    assert_eq!(Depth::Flat.bevel(), Depth::Sunken.bevel());
    assert_ne!(Depth::Flat.fill(), Depth::Sunken.fill());
}

#[test]
fn a_sunken_surface_is_not_a_well() {
    // Authored in opposite directions: makeover derives surface-well by
    // inverting against the theme's content colour, while surface-sunken is
    // authored and may sit darker than raised.
    assert_ne!(Fill::Sunken, Fill::Well);
    assert_eq!(Fill::Sunken.token(), "surface-sunken");
    assert_eq!(Fill::Well.token(), "surface-well");
}

#[test]
fn every_selector_describes_both_of_its_states() {
    // The gap 0.3.0 closed. Before it, only `chosen` existed and the
    // unchosen option fell through to Flat at every renderer.
    for s in [Selector::Tabs, Selector::Segmented, Selector::Toggle] {
        assert_ne!(
            s.chosen(),
            s.unchosen(),
            "{s:?} cannot tell picked from unpicked"
        );
    }
}

#[test]
fn only_a_tab_inverts_the_other_way() {
    // Tabs recede so the chosen one comes forward; a segment and a toggle
    // stand up so the chosen one is held in. That inversion is the whole
    // content of "picked" once colour is deferred, and it is why the three
    // are not one member with a flag.
    assert_eq!(Selector::Tabs.unchosen(), Depth::Sunken);
    assert_eq!(Selector::Tabs.chosen(), Depth::Raised);

    for s in [Selector::Segmented, Selector::Toggle] {
        assert_eq!(s.unchosen(), Depth::Raised);
        assert_eq!(s.chosen(), Depth::Well);
        // Held in is what pressing produces: one appearance, two reasons.
        assert_eq!(s.unchosen().pressed(), s.chosen());
    }
}

#[test]
fn pressing_a_card_makes_a_well() {
    assert_eq!(Depth::Raised.pressed(), Depth::Well);
    assert_eq!(
        Depth::Raised.pressed().bevel(),
        Depth::Raised.bevel().map(Bevel::pressed)
    );
    // Only raised regions respond to being pressed.
    assert_eq!(Depth::Flat.pressed(), Depth::Flat);
    assert_eq!(Depth::Well.pressed(), Depth::Well);
    // An overlay is a surface, not a control.
    assert_eq!(Depth::Overlay.pressed(), Depth::Overlay);
}

#[test]
fn an_overlay_is_lifted_rather_than_edged() {
    // The wave-2 rule: a surface over the page takes elevation, a surface
    // in the page takes a bevel. Both halves come off the one Depth, so
    // they cannot disagree.
    assert_eq!(Depth::Overlay.fill(), Some(Fill::Overlay));
    assert_eq!(Depth::Overlay.bevel(), None);

    // Three depths have no bevel and they are not the same claim. Flat has
    // nothing to separate from, Sunken's colour is doing the separating,
    // and an overlay is separated by the lift.
    assert_ne!(Depth::Overlay.fill(), Depth::Sunken.fill());
    assert_ne!(Depth::Overlay.fill(), Depth::Flat.fill());
}

#[test]
fn a_note_is_neither_a_hint_nor_an_error() {
    // audiofiles' export Format field: choosing WAV over Original
    // re-encodes and drops the embedded metadata. Perfectly valid, and it
    // costs something.
    let format = Field {
        note: Some((Tone::Warning, "Re-encoding drops embedded BWF and iXML")),
        ..Field::select("format", "Format", &[])
    };
    assert!(!format.invalid(), "a note is not a validation failure");
    assert!(format.hint.is_none());
    assert!(format.error.is_none());
    assert_eq!(format.note.unwrap().0, Tone::Warning);

    // The default is no note, so the 15 in-tree `..Field::new(..)`
    // literals absorb the member with no call-site edit.
    assert!(Field::new(FieldKind::Text, "title", "Title").note.is_none());
}

#[test]
fn neutral_is_content_not_muted_content() {
    // Neutral means "no status", and that is all it means. It answered
    // `content-muted` until 2026-08-27, which muted a figure's headline
    // number to the colour of its own caption. What makes a badge quiet
    // is `Token::Badge` answering no click, which lives on the renderer.
    assert_eq!(Tone::Neutral.token(), "content");
    assert!(!Token::Badge.interactive());
    assert_eq!(State::Disabled.token(), "content-muted");
}

#[test]
fn intents_name_makeover_tokens_and_nothing_else() {
    assert_eq!(Edge::Light.token(), "bevel-light");
    assert_eq!(Edge::Dark.token(), "bevel-dark");
    assert_eq!(Fill::Raised.token(), "surface-raised");
    assert_eq!(Fill::Well.token(), "surface-well");
    // No value ever leaves this crate.
    for t in [
        Edge::Light.token(),
        Edge::Dark.token(),
        Tone::Danger.token(),
        Tone::Neutral.token(),
        State::Disabled.token(),
    ] {
        assert!(!t.starts_with('#'), "{t} looks like a value");
        assert!(
            !t.chars().next().unwrap().is_ascii_digit(),
            "{t} is a value"
        );
    }
}

#[test]
fn a_badge_cannot_be_pressed_and_a_chip_latches() {
    // The one line that runs through all three apps' taxonomies.
    assert!(!Token::Badge.interactive());
    assert!(Token::Chip { removable: false }.interactive());
    assert!(Token::Chip { removable: true }.interactive());

    // A badge is a label, so giving it an edge would lie about it.
    assert_eq!(Token::Badge.depth(false), Depth::Flat);
    assert_eq!(Token::Badge.depth(true), Depth::Flat);

    // A latched chip wears the same shape a pressed one does.
    let chip = Token::Chip { removable: false };
    assert_eq!(chip.depth(false), Depth::Raised);
    assert_eq!(chip.depth(true), Depth::Raised.pressed());
}

#[test]
fn a_toast_and_a_banner_differ_in_more_than_placement() {
    assert!(Notice::Toast.transient());
    assert!(!Notice::Banner.transient());
    // A toast floats above the page; a banner rests in the flow.
    assert_eq!(Notice::Toast.fill(), Fill::Overlay);
    assert_eq!(Notice::Banner.fill(), Fill::Raised);
}

#[test]
fn emphasis_falls_off_down_the_row() {
    // `revealed_on_hover` was asserted here until 0.13.0 retired it. It said
    // a row's actions stay hidden until hover, which stopped being true when
    // makeover-webview 0.23.0 showed them at rest, and nothing had consumed
    // it for a release either way.
    assert_eq!(RowPart::Primary.intent(), "content");
    assert_eq!(RowPart::Secondary.intent(), "content-secondary");
    assert_eq!(RowPart::Meta.intent(), "content-muted");
}

#[test]
fn a_token_part_carries_no_intent_of_its_own() {
    // Each token carries its own tone, so a part-level intent underneath
    // would fight the thing sitting on it. Same reasoning as actions, which
    // is why they answer alike.
    assert_eq!(RowPart::Tokens.intent(), RowPart::Actions.intent());
    assert_eq!(RowPart::Tokens.intent(), "content");
}

#[test]
fn the_two_temporal_kinds_are_the_two_that_name_a_moment() {
    // The pair is named once so a host with parsing to do asks here rather
    // than spelling it out, which is `offers_options`' reason.
    assert!(FieldKind::Date.temporal());
    assert!(FieldKind::DateTime.temporal());

    for kind in [
        FieldKind::Text,
        FieldKind::Secret,
        FieldKind::Number,
        FieldKind::Email,
        FieldKind::Url,
        FieldKind::Tel,
        FieldKind::Range,
        FieldKind::Textarea,
        FieldKind::Rich,
        FieldKind::Select,
        FieldKind::Radio,
        FieldKind::Checkbox,
        FieldKind::File,
        FieldKind::Hidden,
    ] {
        assert!(!kind.temporal(), "{kind:?}");
    }
}

#[test]
fn a_date_carries_no_time_and_a_datetime_carries_no_zone() {
    // The formats are the whole reason the members are worth naming apart
    // from text, so the doc comments and the constants have to agree. A
    // host reading one and meeting the other is the silent failure.
    assert_eq!(DATE_FORMAT, "%Y-%m-%d");
    assert!(!DATE_FORMAT.contains("%H"), "a day carries no hour");

    assert_eq!(DATETIME_FORMAT, "%Y-%m-%dT%H:%M");
    assert!(
        DATETIME_FORMAT.starts_with(DATE_FORMAT),
        "a moment starts with the day it is on"
    );
    // Local, and that is a property of the value rather than an omission.
    assert!(!DATETIME_FORMAT.contains("%Z"), "no zone name");
    assert!(!DATETIME_FORMAT.ends_with('Z'), "not UTC-stamped");
    assert!(!DATETIME_FORMAT.contains("%S"), "no seconds by default");
}

#[test]
fn a_temporal_kind_takes_a_label_above_it_and_offers_no_options() {
    // Neither is a checkbox and neither is a fixed set, so both fall where
    // text does. Asserted because a new kind lands in three predicates and
    // only one of them is the interesting one.
    for kind in [FieldKind::Date, FieldKind::DateTime] {
        assert!(kind.visible(), "{kind:?}");
        assert!(!kind.confidential(), "{kind:?}");
        assert!(!kind.labels_itself(), "{kind:?}");
        assert!(!kind.offers_options(), "{kind:?}");
    }
}

#[test]
fn a_cell_part_names_an_intent_and_only_the_value_is_text() {
    // The table half of what RowPart::intent does for rows. A cell holding
    // a control and a cell holding text answered alike until 0.14.0, and a
    // control in a cell took the cell's text colour.
    assert_eq!(CellPart::Value.intent(), "content");

    for part in [CellPart::Tokens, CellPart::Actions, CellPart::Link] {
        // Each for its own reason -- a token carries its tone, an action is
        // a control, a link takes the action colour -- and all three reach
        // the intent inheriting already gives.
        assert_eq!(part.intent(), CellPart::Value.intent(), "{part:?}");
    }
}

#[test]
fn every_cell_part_answers_with_a_token_and_never_a_value() {
    for part in [
        CellPart::Value,
        CellPart::Tokens,
        CellPart::Actions,
        CellPart::Link,
    ] {
        let intent = part.intent();
        assert!(!intent.is_empty(), "{part:?} names nothing");
        assert!(!intent.starts_with('#'), "{part:?} looks like a value");
    }
}

#[test]
fn a_separator_is_what_tells_a_section_from_a_subsection() {
    assert!(Heading::Section.separated());
    assert!(!Heading::Subsection.separated());
    assert!(!Heading::Page.separated());
}

#[test]
fn a_chosen_segment_is_held_in_and_a_chosen_tab_comes_forward() {
    assert_eq!(Selector::Segmented.chosen(), Depth::Well);
    assert_eq!(Selector::Toggle.chosen(), Depth::Well);
    // The exception, and the whole folder semantic: the open tab joins its
    // pane rather than sinking away from it.
    assert_eq!(Selector::Tabs.chosen(), Depth::Raised);

    // A held-in segment is indistinguishable from a pressed raised one,
    // which is the economy the light model buys over a colour swap.
    assert_eq!(Selector::Segmented.chosen(), Depth::Raised.pressed());

    // A toggle stands alone; the other two are built out of parts that
    // touch.
    assert!(Selector::Segmented.abutting());
    assert!(Selector::Tabs.abutting());
    assert!(!Selector::Toggle.abutting());
}

#[test]
fn columns_are_peers_and_a_split_is_not() {
    // The distinction the member exists for. A split's two panes stand in a
    // master-detail relationship; columns choose nothing about each other.
    // Both are flat, so depth cannot tell them apart and the doc has to.
    assert_eq!(Region::Columns.depth(), Depth::Flat);
    assert_eq!(Region::Split.depth(), Depth::Flat);
    assert_ne!(Region::Columns, Region::Split);
}

#[test]
fn columns_carry_no_count_and_no_share() {
    // The two things a board is always asked to carry and must not. How
    // many is what the children say; how wide is settled by "peers are
    // equal".
    //
    // The guard is the binding itself and it is a compile-time one: adding
    // a field to `Columns` stops this line compiling, which is a better
    // failure than any assertion about it. Written out rather than inlined
    // for exactly that reason.
    let columns: Region<'_> = Region::Columns;
    assert_eq!(columns.name(), None);
}

#[test]
fn columns_are_described_and_the_escape_hatch_is_still_one_member() {
    // A board's contents are ordinary description all the way down, so a
    // renderer that does not lay them across still draws every column.
    // Stacking them vertically is honouring this member, not degrading it.
    assert!(Region::Columns.described());
    assert!(!Region::Handover { name: "timeline" }.described());
}

#[test]
fn a_span_never_has_zero_minutes_however_it_is_asked_for() {
    // Every renderer divides by this. A caller passing a backwards or empty
    // span is a bug, but it is not a bug worth a panic three renderers deep.
    assert_eq!(Span::new(600, 600).length(), 1);
    assert_eq!(Span::new(600, 300).length(), 1);
    assert_eq!(Span::DAY.length(), 1440);
}

#[test]
fn a_span_can_run_past_midnight_without_a_second_date() {
    // 22:00 to 02:00. The alternative was carrying a date, which drags a
    // timezone into the vocabulary for the sake of one night shift.
    let overnight = Span::new(1320, 1560);
    assert_eq!(overnight.length(), 240);
    assert!(overnight.holds(1500));
    assert!(!overnight.holds(1200));
}

#[test]
fn overlap_is_computed_rather_than_declared() {
    // The reason Placement carries no `conflicts` flag: the times already
    // say it, and a second source for one fact is how a stale conflict
    // badge outlives the conflict.
    let morning = Placement::new(540, 60); // 09:00-10:00
    let overlapping = Placement::new(570, 60); // 09:30-10:30
    let after = Placement::new(600, 60); // 10:00-11:00

    assert!(morning.overlaps(overlapping));
    assert!(overlapping.overlaps(morning), "overlap is symmetric");
    // Touching end to end is not overlapping: `to` is exclusive, so a
    // 10:00 start does not collide with a 10:00 end.
    assert!(!morning.overlaps(after));
    assert!(!after.overlaps(morning));
}

#[test]
fn a_placement_is_always_drawable() {
    assert_eq!(Placement::new(540, 0).length(), 1);
    assert_eq!(Placement::new(540, 30).end(), 570);
}

#[test]
fn a_track_places_the_fraction_every_renderer_would_otherwise_compute() {
    let day = Track::DAY;
    assert!((day.fraction(0) - 0.0).abs() < f32::EPSILON);
    assert!((day.fraction(720) - 0.5).abs() < f32::EPSILON);
    // Clamped rather than off the end: an event running past the span's
    // close draws at the edge, which beats panicking or drawing nowhere.
    assert!((day.fraction(2000) - 1.0).abs() < f32::EPSILON);
}

#[test]
fn a_track_counts_its_slots_and_never_divides_by_zero() {
    assert_eq!(Track::DAY.slots(), 96);
    assert_eq!(Track::over(Span::new(540, 1020)).slots(), 32);
    // A span that does not divide evenly keeps a slot for its tail.
    assert_eq!(Track::over(Span::new(0, 50)).slots(), 4);
    // slot: 0 is a caller bug that reads as one slot, not a panic.
    let degenerate = Track {
        span: Span::DAY,
        slot: 0,
        tick: 60,
        unit: Unit::Minutes,
    };
    assert_eq!(degenerate.slots(), 1);
}

#[test]
fn a_track_carries_facts_and_no_presentation() {
    // The guard on the thing the withdrawn refusal was right about. If a
    // pixel measure, a scroll offset or a colour ever lands on Track, the
    // member has stopped being a fact about the data and the timeline
    // really has become a component library wearing a description's name.
    let day = Track::DAY;
    assert_eq!(day.span, Span::DAY);
    assert_eq!(day.slot, 15);
    assert_eq!(day.tick, 60);
    assert_eq!(day.unit, Unit::Minutes);

    // Three fields when this was written, and the fourth came here to say
    // why, which is the whole point of the assertion. `unit` is what the
    // integers COUNT -- a fact about the data, unavailable from the numbers
    // themselves, and the absence of it is what let a month strip render
    // under a wall clock. A fifth field still has to argue, and "the
    // renderer would find it handy" is still not the argument.
    // Destructured rather than rebuilt: this is the form that names every
    // field and stops compiling when a fifth arrives, without binding
    // anything a lint has to forgive.
    let Track {
        span: _,
        slot: _,
        tick: _,
        unit: _,
    } = day;
}

#[test]
fn a_day_strip_is_the_same_arithmetic_under_a_different_unit() {
    // The probe that found the defect, kept as a test. Fifteen days from
    // day three, on a thirty-one day month: the geometry was always right
    // and only the label was wrong, which is why `unit` is a fact and not
    // presentation.
    let march = Track::days(Span::new(0, 31));
    assert_eq!(march.slots(), 31);
    assert_eq!(march.unit, Unit::Days);

    let leave = Placement::new(2, 15);
    assert!((march.fraction(leave.at()) - 2.0 / 31.0).abs() < 0.0001);
    assert!((march.fraction(leave.end()) - 17.0 / 31.0).abs() < 0.0001);
}

#[test]
fn a_pane_is_looked_into_and_a_band_is_not() {
    assert_eq!(Region::Pane.depth(), Depth::Well);
    assert_eq!(Region::Modal.depth(), Depth::Raised);
    for r in [
        Region::Band,
        Region::Sidebar,
        Region::Group,
        Region::Split,
        Region::TabGroup,
    ] {
        assert_eq!(r.depth(), Depth::Flat, "{r:?} should carry no edge");
    }
}

#[test]
fn exactly_one_region_is_opaque() {
    // The escape hatch is one member and stays one member. If a second
    // undescribed region ever appears, the description has started
    // conceding rather than deferring.
    for r in [
        Region::Band,
        Region::Sidebar,
        Region::Pane,
        Region::Group,
        Region::Split,
        Region::TabGroup,
        Region::Modal,
        // A widget is described, and that is the whole of what separates it
        // from a bespoke here. Both carry a name this crate never reads;
        // only one of them has contents under it that a renderer which does
        // not know the name can still walk.
        Region::Widget { name: "carousel" },
    ] {
        assert!(r.described(), "{r:?} should be describable");
    }
    assert!(!Region::Handover { name: "day-plan" }.described());
}

#[test]
fn a_region_nobody_converted_yet_is_not_a_region_the_app_gave_up_on() {
    // The whole of why this is two members. Both are opaque and neither is
    // described, so the old single member made them one value; a renderer
    // with no fill drew both as an empty box and said nothing either way.
    assert!(Region::Handover { name: "day-plan" }.owed());
    assert!(
        !Region::Ceded {
            name: "revenue-chart"
        }
        .owed()
    );

    // Everything that carries its own contents owes nothing, which is the
    // reading a renderer needs for the members it already draws.
    assert!(!Region::Pane.owed());
    assert!(!Region::Widget { name: "carousel" }.owed());

    // Opaqueness is the axis they still share.
    assert!(!Region::Ceded { name: "waveform" }.described());
    assert_eq!(Region::Ceded { name: "waveform" }.name(), Some("waveform"));
    assert_eq!(Region::Ceded { name: "waveform" }.depth(), Depth::Flat);
}

#[test]
fn a_group_contains_a_section_without_claiming_to_be_a_pane() {
    // The whole of why this is a member rather than a `Pane`. A pane is
    // looked into and scrolls; a group is neither, and four groups inside a
    // settings pane described as panes are four wells inside a well.
    assert_eq!(Region::Pane.depth(), Depth::Well);
    assert_eq!(Region::Group.depth(), Depth::Flat);
    assert_ne!(Region::Group, Region::Pane);

    // Described, and it carries no name: a group is a primitive every
    // renderer draws from scratch, which is what separates it from the two
    // members that do carry one.
    assert!(Region::Group.described());
    assert_eq!(Region::Group.name(), None);
}

#[test]
fn a_section_heading_names_a_block_that_now_exists() {
    // `Heading::Section` has said "names a block within the screen" since
    // 0.2.0 and there was no block. The pairing is the point, and it is the
    // reason a group carries no heading of its own: the heading is an
    // ordinary node in the body, and a group without one is legal.
    assert!(Heading::Section.separated());
    assert_eq!(Region::Group.depth(), Depth::Flat);
}

#[test]
fn a_widget_inherits_its_depth_the_way_a_bespoke_does() {
    // Stronger than the bespoke case: a widget is drawn by whichever
    // renderer recognises the name, so a depth chosen here would be this
    // crate deciding a carousel is raised on every host.
    assert_eq!(Region::Widget { name: "carousel" }.depth(), Depth::Flat);
    assert_eq!(Region::Widget { name: "pager" }.depth(), Depth::Flat);
}

#[test]
fn a_name_is_readable_without_asking_which_member_carried_it() {
    // A renderer dispatching on a name wants the string, not the member.
    // Writing that `matches!` at each renderer is how the two drift apart.
    assert_eq!(Region::Widget { name: "carousel" }.name(), Some("carousel"));
    assert_eq!(
        Region::Handover { name: "day-plan" }.name(),
        Some("day-plan")
    );

    for r in [
        Region::Band,
        Region::Sidebar,
        Region::Pane,
        Region::Group,
        Region::Split,
        Region::TabGroup,
        Region::Modal,
    ] {
        assert_eq!(r.name(), None, "{r:?} names nothing an app chose");
    }
}

#[test]
fn a_bespoke_region_inherits_its_depth_rather_than_choosing_one() {
    // The app owns the contents, not the placement. An app that wants its
    // timeline in a well frames it in a Pane.
    assert_eq!(Region::Handover { name: "day-plan" }.depth(), Depth::Flat);
    assert_eq!(Region::Handover { name: "kanban" }.depth(), Depth::Flat);
}

#[test]
fn a_screen_with_a_bespoke_region_is_still_a_whole_screen() {
    // The argument the member exists for: goingson's day-plan has to be
    // routable, or the description covers only the boring screens and the
    // interesting four need a second path beside the router.
    let day_plan = [
        Region::Band,
        Region::Handover { name: "day-plan" },
        Region::Sidebar,
    ];
    assert_eq!(day_plan.iter().filter(|r| r.described()).count(), 2);
    assert_eq!(day_plan.iter().filter(|r| !r.described()).count(), 1);
}

#[test]
fn a_secret_field_is_marked_as_one_and_a_hidden_field_is_not_drawn() {
    let secret = Field::new(FieldKind::Secret, "password", "Password");
    assert!(secret.kind.confidential());
    assert!(secret.kind.visible());

    assert!(!FieldKind::Hidden.visible());
    // Nothing else is confidential, or the marker means nothing.
    for k in [
        FieldKind::Text,
        FieldKind::Number,
        FieldKind::Textarea,
        FieldKind::Rich,
        FieldKind::Select,
        FieldKind::Checkbox,
        FieldKind::Hidden,
    ] {
        assert!(!k.confidential(), "{k:?} should not be confidential");
    }

    // Only a checkbox carries its own label.
    assert!(FieldKind::Checkbox.labels_itself());
    assert!(!FieldKind::Text.labels_itself());
}

#[test]
fn a_plain_field_offers_nothing_and_a_select_offers_its_options() {
    let text = Field::new(FieldKind::Text, "title", "Title");
    assert!(text.options.is_empty());
    assert_eq!(text.placeholder, None);

    let sizes = [Choice::plain("small"), Choice::plain("large")];
    let select = Field::select("size", "Size", &sizes);
    assert_eq!(select.kind, FieldKind::Select);
    assert_eq!(select.options.len(), 2);
}

#[test]
fn a_choice_says_what_submits_and_what_is_read_apart() {
    // The whole reason it is two strings. `plain` is the case where they
    // coincide, and it is a shorthand rather than the general shape.
    let plain = Choice::plain("7");
    assert_eq!((plain.value, plain.label), ("7", "7"));

    let spelled = Choice::new("7", "One week");
    assert_ne!(spelled.value, spelled.label);
    assert!(
        spelled.available(),
        "an option is pickable until it says not"
    );
}

#[test]
fn a_candidate_carries_the_line_that_tells_it_from_its_neighbours() {
    // The gap this type was born for: two candidates whose labels read
    // alike, told apart by the second string and by nothing else. The
    // measured site is the MNW tag box, where "Format" is a leaf under
    // audio, software, writing and video.
    let audio = Candidate::new("audio/format", "Format").detailed("Audio");
    let writing = Candidate::new("writing/format", "Format").detailed("Writing");

    assert_eq!(audio.label, writing.label);
    assert_ne!(audio.detail, writing.detail);
    assert_ne!(
        audio, writing,
        "two rows a user cannot tell apart are two rows the type can"
    );
}

#[test]
fn a_candidate_is_read_differently_from_an_option_and_written_the_same() {
    // The ruling's own distinction, held as a test so the two types do not
    // drift back together. Submitting is identical; the second line is the
    // whole of what differs, and it is absent by default because a list of
    // distinct labels wants nothing there.
    let candidate = Candidate::plain("rust");
    assert_eq!((candidate.value, candidate.label), ("rust", "rust"));
    assert_eq!(
        candidate.detail, None,
        "one line unless the route says otherwise"
    );

    let option = Choice::plain("rust");
    assert_eq!(
        (candidate.value, candidate.label),
        (option.value, option.label)
    );
}

#[test]
fn a_radio_asks_the_same_question_as_a_select_and_is_not_the_same_kind() {
    // Both offer a fixed set and both read `options`, so the two
    // constructors differ in exactly one thing. That one thing is the
    // point: a renderer decides whether the alternatives are readable
    // without opening anything, and it can only decide that if the
    // description said which question was asked.
    let styles = [
        Choice::new("copy", "Copy samples in"),
        Choice::new("reference", "Reference in place"),
    ];
    let radio = Field::radio("storage", "Storage style", &styles);
    let select = Field::select("storage", "Storage style", &styles);

    assert_eq!(radio.kind, FieldKind::Radio);
    assert_ne!(radio.kind, select.kind);
    assert_eq!(radio.options, select.options);
    assert_eq!(
        Field {
            kind: select.kind,
            ..radio
        },
        select
    );
}

#[test]
fn an_unavailable_option_cannot_be_silent_about_it() {
    // The whole content of the one-member shape: saying an option is not
    // pickable and saying why are the same act, so the greyed-out-with-no-
    // reason state is unsayable rather than merely discouraged.
    let multi =
        Choice::new("multi", "Multi-sample").unless("Drop a second sample onto the keyboard.");
    assert!(!multi.available());
    assert_eq!(
        multi.unavailable,
        Some("Drop a second sample onto the keyboard.")
    );

    // And the option is still in the list, carrying what it submits, so a
    // renderer draws it rather than the app dropping it.
    assert_eq!(multi.value, "multi");
    assert_eq!(multi.label, "Multi-sample");
}

#[test]
fn an_option_can_say_what_picking_it_means_and_why_it_cannot_be_picked() {
    // `5e21dcfc`. Two different sentences about one option, and an option
    // that has both has said two things: what the tier is, and that it is
    // not available yet. Folding them would be the label-folding this
    // member exists to end.
    let tier = Choice::new("24", "Small Files")
        .detailing("$24/mo. 2GB/file, 100GB total. Fits audio, plugins, binaries.")
        .unless("Sold out while the founder window is open.");

    assert_eq!(
        tier.detail,
        Some("$24/mo. 2GB/file, 100GB total. Fits audio, plugins, binaries.")
    );
    assert_eq!(
        tier.unavailable,
        Some("Sold out while the founder window is open.")
    );
    assert!(!tier.available());

    // Neither is implied by the other, which is what keeps a renderer from
    // reading a detail as a reason: an ordinary option with a second line
    // is still pickable.
    let plain = Choice::new("free", "Free").detailing("No charge. Available to everyone.");
    assert!(plain.available());
    assert_eq!(plain.detail, Some("No charge. Available to everyone."));
    assert_eq!(Choice::new("free", "Free").detail, None);
}

#[test]
fn a_range_carries_both_ends_and_a_validated_number_need_not() {
    // The distinction the kind exists for, asserted rather than only
    // written down: bounds are a rule for one and the control itself for
    // the other.
    let threshold = Field::range("review", "Review above", "0", "1");
    assert_eq!(threshold.kind, FieldKind::Range);
    assert!(threshold.bounded());
    assert_eq!(threshold.min, Some("0"));
    assert_eq!(threshold.max, Some("1"));
    // Granularity is the host's until an app says otherwise.
    assert_eq!(threshold.step, None);

    // goingson's duration: a typed number with a floor, and it must not
    // read as a slider.
    let minutes = Field {
        min: Some("1"),
        ..Field::new(FieldKind::Number, "minutes", "Minutes")
    };
    assert_ne!(minutes.kind, FieldKind::Range);
    assert!(!minutes.bounded(), "one end is a rule, not an extent");
}

#[test]
fn a_range_described_with_one_end_says_so_rather_than_being_refused() {
    // Nothing here enforces the pair, for the reason nothing here enforces
    // `required`: the description states the constraint and the renderer
    // asks. What it must not do is look bounded.
    let half = Field {
        max: Some("1"),
        ..Field::new(FieldKind::Range, "review", "Review above")
    };
    assert!(!half.bounded());
}

#[test]
fn exactly_the_option_taking_kinds_say_so() {
    // The renderers branch on this rather than on a list of their own, so
    // a kind added without a decision here renders its options nowhere.
    assert!(FieldKind::Select.offers_options());
    assert!(FieldKind::Radio.offers_options());
    for kind in [
        FieldKind::Text,
        FieldKind::Secret,
        FieldKind::Number,
        FieldKind::Email,
        FieldKind::Url,
        FieldKind::Tel,
        FieldKind::Range,
        FieldKind::Textarea,
        FieldKind::Rich,
        FieldKind::Checkbox,
        FieldKind::Hidden,
    ] {
        assert!(!kind.offers_options(), "{kind:?} does not offer options");
    }
}

#[test]
fn a_radio_group_takes_a_label_even_though_its_options_carry_their_own() {
    // The near-miss: each option is labelled beside its own button, so a
    // renderer could plausibly read the group as self-labelling and drop
    // the question. Checkbox is the only kind that does that.
    assert!(!FieldKind::Radio.labels_itself());
    assert!(FieldKind::Checkbox.labels_itself());
}

#[test]
fn a_select_with_no_options_is_sayable() {
    // An app whose option list has not loaded has exactly this. Making it
    // unrepresentable would push the state somewhere less visible, and a
    // renderer drawing an empty select reports it on screen.
    let loading = Field::select("project", "Project", &[]);
    assert!(loading.options.is_empty());
}

#[test]
fn the_description_carries_the_question_and_never_the_answer() {
    // The line 0.8.0 drew. Placeholder and options are properties of what
    // is being asked; the current value is what came back, and no field
    // here holds one.
    let f = Field {
        placeholder: Some("yyyy-mm-dd"),
        ..Field::new(FieldKind::Text, "due", "Due")
    };
    assert_eq!(f.placeholder, Some("yyyy-mm-dd"));
    // A placeholder is not a label, and having one does not excuse the
    // field from carrying the other.
    assert_eq!(f.label, "Due");
}

#[test]
fn a_field_reports_its_own_error_state() {
    let mut f = Field::new(FieldKind::Text, "title", "Title");
    assert!(!f.invalid());
    f.error = Some("Required");
    assert!(f.invalid());
}

#[test]
fn columns_drop_by_priority_and_never_by_position() {
    let cols = [
        Column {
            width: Width::Fill,
            priority: Priority::Essential,
            kind: ColumnKind::Text,
            ..Column::new("Title")
        },
        Column {
            width: Width::Fixed,
            priority: Priority::Secondary,
            kind: ColumnKind::Text,
            ..Column::new("Due")
        },
        Column {
            width: Width::Fixed,
            priority: Priority::Optional,
            kind: ColumnKind::Text,
            ..Column::new("Estimate")
        },
    ];

    // Widest: everything survives.
    assert_eq!(
        cols.iter()
            .filter(|c| c.kept_at(Priority::Optional))
            .count(),
        3
    );
    // Narrower: the optional column goes first.
    let kept: Vec<_> = cols
        .iter()
        .filter(|c| c.kept_at(Priority::Secondary))
        .map(|c| c.name)
        .collect();
    assert_eq!(kept, ["Title", "Due"]);
    // Narrowest: only what identifies the row.
    let kept: Vec<_> = cols
        .iter()
        .filter(|c| c.kept_at(Priority::Essential))
        .map(|c| c.name)
        .collect();
    assert_eq!(kept, ["Title"]);
}

#[test]
fn inserting_a_column_does_not_move_what_gets_dropped() {
    // The bug the ordinal form has and this form cannot: goingson hides
    // `nth-child(n+5)` against a seven-column table, so a column inserted
    // anywhere to the left silently hides a different one.
    let before = [
        Column::new("Title"),
        Column {
            width: Width::Fixed,
            priority: Priority::Optional,
            kind: ColumnKind::Text,
            ..Column::new("Estimate")
        },
    ];
    let after = [
        Column::new("Title"),
        Column::new("Project"), // inserted
        Column {
            width: Width::Fixed,
            priority: Priority::Optional,
            kind: ColumnKind::Text,
            ..Column::new("Estimate")
        },
    ];

    fn dropped<'a>(cols: &[Column<'a>]) -> Vec<&'a str> {
        cols.iter()
            .filter(|c| !c.kept_at(Priority::Secondary))
            .map(|c| c.name)
            .collect()
    }
    assert_eq!(dropped(&before), ["Estimate"]);
    assert_eq!(dropped(&after), ["Estimate"]);
}

#[test]
fn an_arrangement_carries_the_tab_group_as_a_modifier() {
    // goingson uses the tab group inside the content region rather than
    // instead of one, so it is not a third arrangement.
    let go = Arrangement::list_detail(true);
    let plain = Arrangement::list_detail(false);
    assert_ne!(go, plain);
    assert_ne!(go, Arrangement::sidebar_content());
}

#[test]
fn a_share_is_a_proportion_and_resolves_the_same_way_everywhere() {
    // The point of the member: a terminal reading columns and a webview
    // reading a grid honour one fact, so two hosts showing one screen agree
    // about its proportions.
    assert_eq!(Share::LIST.as_percent(), 40);
    assert_eq!(Share::LIST.of(100), 40);
    assert_eq!(
        Share::SIDEBAR.of(96),
        24,
        "quasi-tui's 24 columns, said as a quarter"
    );
}

#[test]
fn a_region_never_resolves_to_nothing() {
    // A region the description named should be visible. A zero-width one
    // reads on screen as a region that vanished, which is the hardest kind
    // of bug to find from what is drawn.
    assert_eq!(Share::percent(5).of(1), 1);
    assert_eq!(Share::percent(5).of(0), 1);
}

#[test]
fn a_share_outside_the_range_is_clamped_rather_than_refused() {
    assert_eq!(Share::percent(0), Share::percent(5));
    assert_eq!(Share::percent(200), Share::percent(95));
}

#[test]
fn the_share_rides_on_the_arrangement_that_knows_which_question_it_is() {
    // How much a sidebar takes and how much a list side takes are different
    // questions, and this enum is the only thing that knows which is being
    // asked.
    assert_eq!(Arrangement::sidebar_content().share(), Some(Share::SIDEBAR));
    assert_eq!(Arrangement::list_detail(false).share(), Some(Share::LIST));
    // One region divides nothing, so there is no share to answer with.
    assert_eq!(Arrangement::Single.share(), None);
    assert_eq!(
        Arrangement::Single.with_share(Share::percent(20)),
        Arrangement::Single
    );

    let narrow = Arrangement::sidebar_content().with_share(Share::percent(20));
    assert_eq!(narrow.share(), Some(Share::percent(20)));
    assert!(matches!(narrow, Arrangement::SidebarContent { .. }));
}

#[test]
fn a_measure_defaults_to_the_one_53_of_69_templates_asked_for() {
    // The default is meaningful: a screen nobody said anything about uses
    // the window it was given.
    assert_eq!(Measure::default(), Measure::Wide);
    assert_eq!(Measure::Reading.as_str(), "reading");
}

#[test]
fn readiness_names_the_state_and_not_the_shimmer() {
    // Two members and no third. If a skeleton ever appears in this enum,
    // the deferral rule has been broken.
    assert_ne!(Readiness::Ready, Readiness::Pending);
}

#[test]
fn a_window_with_no_length_still_answers_what_it_can() {
    // The uncounted case is the common one, not the degenerate one: a query
    // that asked for 51 to learn there were more than 50 knows there are,
    // and not how many.
    let uncounted = Window::new(100, 50);
    assert_eq!(uncounted.index(), Some(2));
    assert_eq!(uncounted.windows(), None);
    assert!(uncounted.has_before());
    // Unknown length cannot rule out more, and offering a way forward that
    // turns out empty is the cheaper mistake.
    assert!(uncounted.has_after());
}

#[test]
fn a_counted_window_knows_where_it_ends() {
    let last = Window::new(350, 50).of(400);
    assert_eq!(last.index(), Some(7));
    assert_eq!(last.windows(), Some(8));
    assert!(last.has_before());
    assert!(!last.has_after());

    let first = Window::new(0, 50).of(400);
    assert!(!first.has_before());
    assert!(first.has_after());
}

#[test]
fn a_window_that_does_not_divide_evenly_rounds_up() {
    // 401 rows in pages of 50 is eight pages and a straggler, which is nine
    // pages. Rounding down would make the last one unreachable.
    assert_eq!(Window::new(0, 50).of(401).windows(), Some(9));
}

#[test]
fn a_zero_count_answers_none_rather_than_dividing() {
    let empty = Window::new(0, 0).of(400);
    assert_eq!(empty.index(), None);
    assert_eq!(empty.windows(), None);
    // And it still clamps rather than panicking.
    assert_eq!(Window::new(900, 0).of(400).clamped().from, 399);
}

#[test]
fn a_window_past_the_end_clamps_inside_rather_than_vanishing() {
    // `Slot::current`'s reasoning, one layer down: a description pointing
    // past the end is a host bug, and answering it by drawing nothing
    // reports a region that vanished.
    assert_eq!(Window::new(900, 50).of(400).clamped().from, 350);
    // Nothing to clamp against when the length is unknown.
    assert_eq!(Window::new(900, 50).clamped().from, 900);
}

#[test]
fn a_carousel_frame_is_a_window_of_one() {
    // The shape a carousel instantiates. Same code as a paged list, which is
    // the whole reason `Window` exists rather than two copies of it.
    let third = Window::frame(2, 5);
    assert_eq!(third.index(), Some(2));
    assert_eq!(third.windows(), Some(5));
    assert!(third.has_before());
    assert!(third.has_after());

    let last = Window::frame(4, 5);
    assert!(!last.has_after());
}

#[test]
fn numbered_pages_read_from_one_and_load_more_has_no_page() {
    // The page number is read aloud, so it is one-based; `Window::index` is
    // the zero-based form for indexing.
    let third = Paging::pages(100, 50).of(400);
    assert_eq!(third.page(), Some(3));
    assert_eq!(third.pages_total(), Some(8));
    assert_eq!(third.total(), Some(400));
    assert!(third.has_previous());
    assert!(third.has_more());

    // Load-more grew a window from the start, so "page 2" would name
    // nothing and the type says so rather than inventing one.
    let grown = Paging::more(150).of(400);
    assert_eq!(grown.page(), None);
    assert_eq!(grown.pages_total(), None);
    assert_eq!(grown.shown(), 150);
    assert!(!grown.has_previous());
    assert!(grown.has_more());
}

#[test]
fn an_uncounted_paging_offers_forward_and_admits_no_total() {
    // What a host that will not pay for a COUNT describes. `None` here is
    // permanent: a total arriving later would widen the text that prints it,
    // which is the reflow "first paint is final paint" forbids.
    let feed = Paging::more(50);
    assert_eq!(feed.total(), None);
    assert_eq!(feed.pages_total(), None);
    assert_eq!(feed.remaining(), None);
    assert!(feed.has_more());
}

#[test]
fn what_is_left_is_derived_and_never_underflows() {
    assert_eq!(Paging::more(150).of(400).remaining(), Some(250));
    assert_eq!(Paging::pages(350, 50).of(400).remaining(), Some(0));
    // A host that overshot its own total gets zero rather than a wrapped
    // usize, which would print as "18446744073709551516 remaining".
    assert_eq!(Paging::more(500).of(400).remaining(), Some(0));
}

#[test]
fn a_fallback_is_authored_and_a_group_cannot_omit_it() {
    // No `Default`. The compiler is what enforces rule 2, so the assertion
    // that matters is one this file cannot write; what it can say is that
    // the four authored answers are distinct and none is privileged.
    let all = [
        Fallback::Wrap,
        Fallback::Stack,
        Fallback::Shed,
        Fallback::Menu,
    ];
    for (i, a) in all.iter().enumerate() {
        for b in &all[i + 1..] {
            assert_ne!(a, b);
        }
    }
}

#[test]
fn shedding_stops_at_essential_whatever_the_group_holds() {
    // Priority is read the same way for a group member as for a column,
    // which is the whole claim of generalising it off `Column`.
    let members = [
        ("tabs", Priority::Essential),
        ("search", Priority::Secondary),
        ("count", Priority::Optional),
    ];
    let kept: Vec<_> = members
        .iter()
        .filter(|(_, p)| *p >= Priority::Essential)
        .map(|(n, _)| *n)
        .collect();
    assert_eq!(kept, ["tabs"]);
}

#[test]
fn a_role_says_what_a_part_is_worth_when_the_run_does_not_fit() {
    // The row still identifies itself after everything droppable has gone,
    // which is the property the ladder exists for.
    assert_eq!(RowPart::Primary.priority(), Priority::Essential);
    // A control is not a fact. Room comes out of what the row says, never
    // out of what it offers.
    assert_eq!(RowPart::Actions.priority(), Priority::Essential);
    assert_eq!(RowPart::Meta.priority(), Priority::Optional);
    assert_eq!(RowPart::Proportion.priority(), Priority::Optional);
    assert_eq!(RowPart::Secondary.priority(), Priority::Secondary);
    // Tokens sit in the middle deliberately: a toned badge is often the
    // most scannable thing in a row, so it does not go first.
    assert_eq!(RowPart::Tokens.priority(), Priority::Secondary);
}

#[test]
fn a_run_is_one_line_unless_the_description_says_two() {
    // The default is what every part did before flows existed, so a
    // description written against the old vocabulary keeps its rendering.
    assert_eq!(Flow::default(), Flow::Tight);
    assert_eq!(Flow::Tight.lines(), 1);
    assert_eq!(Flow::Relaxed.lines(), 2);
}

#[test]
fn an_unknown_flow_reads_as_one_line() {
    // `#[non_exhaustive]`'s cost, taken deliberately. A tier added upstream
    // reaches an old renderer as one line rather than as a build break, and
    // one line is the reading that cannot break a neighbour's layout. The
    // match in `lines` is what this holds; it fails if a new tier is given
    // an arm that returns something unbounded.
    for flow in [Flow::Tight, Flow::Relaxed] {
        assert!((1..=2).contains(&flow.lines()));
    }
}

#[test]
fn an_awaiting_mark_is_indeterminate_until_something_is_measured() {
    // The default is the common case: a call waits, and nothing about it is
    // countable. A determinate bar is the exception and says so.
    assert_eq!(Awaiting::default(), Awaiting::unmeasured());
    assert!(!Awaiting::unmeasured().is_determinate());
    assert!(Awaiting::of(40 * 1024 * 1024).is_determinate());
    assert_eq!(Awaiting::of(7).amount, Some(7));
}

// A slider is a fraction and a mapping
//
// `Curve` is the one thing in this crate that computes rather than
// describes, and it does so because four renderers would otherwise each
// write these two formulas and drift. So the formulas are pinned here.

/// The bounds of audiofiles' envelope attack, the curve's first consumer.
const ATTACK: (f64, f64) = (0.001, 5.0);

#[test]
fn a_curve_is_linear_with_no_step_until_a_field_says_otherwise() {
    assert_eq!(Curve::default(), Curve::Linear { step: None });
    let plain = Field::range("t", "T", "0", "1");
    assert_eq!(plain.curve, Curve::Linear { step: None });
    assert_eq!(plain.curve.step(), None);
}

#[test]
fn every_curve_carries_its_own_granularity() {
    assert_eq!(Curve::Linear { step: Some("0.01") }.step(), Some("0.01"));
    assert_eq!(
        Curve::Logarithmic {
            step: Some("0.001")
        }
        .step(),
        Some("0.001")
    );
}

#[test]
fn both_ends_of_the_track_are_the_bounds_under_either_curve() {
    // `min` and `max` are `f(0)` and `f(1)`. That is the whole reframe, and
    // it has to hold for a mapping that is not the identity or the bounds
    // have stopped meaning what the field says they mean.
    let (min, max) = ATTACK;
    for curve in [
        Curve::Linear { step: None },
        Curve::Logarithmic { step: None },
    ] {
        assert!((curve.value_at(0.0, min, max) - min).abs() < 1e-12);
        assert!((curve.value_at(1.0, min, max) - max).abs() < 1e-12);
    }
}

#[test]
fn a_linear_midpoint_is_the_average_and_a_ratio_midpoint_is_the_geometric_mean() {
    let (min, max) = ATTACK;
    let linear = Curve::Linear { step: None }.value_at(0.5, min, max);
    assert!((linear - 2.5005).abs() < 1e-9);

    // The reason the envelope is not linear: half way along a log track is
    // 70 ms, and half way along a linear one is 2.5 seconds. Every attack a
    // sampler is actually played with lives below the first.
    let ratio = Curve::Logarithmic { step: None }.value_at(0.5, min, max);
    assert!((ratio - (min * max).sqrt()).abs() < 1e-12);
    assert!(ratio < 0.08);
}

#[test]
fn a_position_and_a_value_round_trip_under_either_curve() {
    let (min, max) = ATTACK;
    for curve in [
        Curve::Linear { step: None },
        Curve::Logarithmic { step: None },
    ] {
        for position in [0.0, 0.1, 0.25, 0.5, 0.75, 0.99, 1.0] {
            let back = curve.position_of(curve.value_at(position, min, max), min, max);
            assert!(
                (back - position).abs() < 1e-9,
                "{curve:?} lost {position} (got {back})"
            );
        }
    }
}

#[test]
fn a_ratio_curve_across_zero_is_drawn_linearly_rather_than_refused() {
    // An envelope's sustain is a 0-to-1 level. A constant ratio is
    // undefined there, and the answer is the linear mapping rather than a
    // NaN reaching a renderer that would paint it.
    let curve = Curve::Logarithmic { step: None };
    assert!(!curve.is_ratio(0.0, 1.0));
    assert!((curve.value_at(0.5, 0.0, 1.0) - 0.5).abs() < 1e-12);
    assert!(curve.value_at(0.5, -96.0, -20.0).is_finite());
    assert!(curve.is_ratio(ATTACK.0, ATTACK.1));
}

#[test]
fn a_track_with_no_extent_has_one_value_on_it() {
    for curve in [
        Curve::Linear { step: None },
        Curve::Logarithmic { step: None },
    ] {
        assert!((curve.value_at(0.7, 4.0, 4.0) - 4.0).abs() < f64::EPSILON);
        assert!(curve.position_of(4.0, 4.0, 4.0).abs() < f64::EPSILON);
        // Inverted bounds are the same degenerate answer, not a negative
        // extent a renderer would draw backwards.
        assert!((curve.value_at(0.7, 9.0, 2.0) - 9.0).abs() < f64::EPSILON);
    }
}

#[test]
fn a_position_or_a_value_outside_the_track_is_clamped_to_it() {
    let (min, max) = ATTACK;
    let curve = Curve::Logarithmic { step: None };
    assert!((curve.value_at(-3.0, min, max) - min).abs() < 1e-12);
    assert!((curve.value_at(4.0, min, max) - max).abs() < 1e-12);
    assert!(curve.position_of(0.0, min, max).abs() < 1e-12);
    assert!((curve.position_of(500.0, min, max) - 1.0).abs() < 1e-12);
}

#[test]
fn a_typed_number_keeps_its_own_step_and_a_range_reads_its_curve() {
    // The split the 0.32.0 narrowing is: two granularities that were one
    // member, and the kinds that take them do not overlap.
    let typed = Field {
        step: Some("5"),
        ..Field::new(FieldKind::Number, "port", "Port")
    };
    assert_eq!(typed.step, Some("5"));

    let slid = Field {
        curve: Curve::Logarithmic {
            step: Some("0.001"),
        },
        ..Field::range("attack", "Attack", "0.001", "5")
    };
    assert_eq!(slid.step, None);
    assert_eq!(slid.curve.step(), Some("0.001"));
}

#[test]
fn a_theme_picker_offers_themes_and_no_options() {
    // The substitution hazard the constructor exists against: `options` is
    // right there and reads as if it would work, and a renderer walking it
    // for a theme picker draws an empty control.
    let themes = [
        ThemeChoice::new("goingson", "GoingsOn", ThemeVariant::Light, Contrast::High),
        ThemeChoice::new("dracula", "Dracula", ThemeVariant::Dark, Contrast::Standard),
    ];
    let field = Field::theme("theme", "Theme", &themes);

    assert_eq!(field.kind, FieldKind::Theme);
    assert!(field.kind.offers_themes());
    assert!(!field.kind.offers_options());
    assert_eq!(field.themes.len(), 2);
    assert!(field.options.is_empty());
    assert_eq!(field.follows, None);
}

#[test]
fn following_carries_the_store_s_own_spelling() {
    // Not hardcoded here: the value belongs to the app's config table, and
    // this crate holds no facts about somebody else's store.
    let field =
        Field::theme("theme", "Theme", &[]).following(Choice::new("system", "Follow System"));
    let follow = field.follows.expect("the row was offered");
    assert_eq!(follow.value, "system");
    assert_eq!(follow.label, "Follow System");
}

#[test]
fn a_picker_with_nothing_resolved_is_sayable() {
    // A machine whose theme directories hold nothing. The description is
    // true and a renderer says so on screen rather than in a log, which is
    // `Field::options`' own arrangement.
    let field = Field::theme("theme", "Theme", &[]);
    assert!(field.themes.is_empty());
}

#[test]
fn every_kind_but_theme_offers_no_themes() {
    for kind in [
        FieldKind::Text,
        FieldKind::Select,
        FieldKind::Radio,
        FieldKind::Checkbox,
        FieldKind::File,
        FieldKind::Hidden,
    ] {
        assert!(
            !kind.offers_themes(),
            "{kind:?} does not read Field::themes"
        );
    }
}

#[test]
fn a_contrast_tier_reads_worst_first() {
    // Matches `makeover::ContrastTier`, so an adopter's conversion cannot
    // invert an ordering by accident and a sort agrees across the seam.
    assert!(Contrast::Low < Contrast::Standard);
    assert!(Contrast::Standard < Contrast::High);
}

#[test]
fn the_groups_and_badges_have_one_spelling_each() {
    // The whole argument for these living here: three renderers picking
    // their own is one picker reading three ways.
    assert_eq!(ThemeVariant::Light.heading(), "Light");
    assert_eq!(ThemeVariant::Dark.heading(), "Dark");
    assert_eq!(ThemeVariant::HighContrast.heading(), "High Contrast");

    assert_eq!(ThemeVariant::HighContrast.as_str(), "high-contrast");

    assert_eq!(Contrast::High.badge(), "AA");
    assert_eq!(Contrast::Standard.badge(), "OK");
    assert_eq!(Contrast::Low.badge(), "low");
}

#[test]
fn the_variant_spelling_matches_the_theme_file_s_own() {
    // The seam this enum is duplicated across. `makeover::parse_meta` reads
    // `meta.variant` as one of these three strings; a rename on either side
    // that does not move together silently regroups every picker.
    for (variant, spelling) in [
        (ThemeVariant::Light, "light"),
        (ThemeVariant::Dark, "dark"),
        (ThemeVariant::HighContrast, "high-contrast"),
    ] {
        assert_eq!(variant.as_str(), spelling);
        assert_eq!(variant.to_string(), spelling);
    }
}

#[test]
fn a_column_kind_states_the_facts_every_renderer_reads() {
    // wiki `table-model`'s kind table, said as the four facts a host needs.
    assert!(ColumnKind::Number.aligns_end() && ColumnKind::Actions.aligns_end());
    assert!(
        !ColumnKind::Date.wraps(),
        "a date that wraps prints over its neighbour"
    );
    assert!(ColumnKind::Identifier.wraps() && ColumnKind::Identifier.monospace());
    assert!(ColumnKind::Code.monospace() && !ColumnKind::Code.wraps());
    assert!(ColumnKind::Date.tabular() && ColumnKind::Number.tabular());
    assert_eq!(Column::new("x").kind, ColumnKind::Text);
}