1 files changed, 176 insertions, 0 deletions
diff --git a/rust/crates/graphics/tests/gradient_stops.rs b/rust/crates/graphics/tests/gradient_stops.rs
new file mode 100644
index 00000000..04adc893
--- /dev/null
+++ b/rust/crates/graphics/tests/gradient_stops.rs
@@ -0,0 +1,176 @@
+use graphics::gradient::ast::{Color, ColorStop, Distance};
+use graphics::gradient::stops::{color_to_string, normalize_color_stops};
+
+fn stop(color: Color, length: Option<Distance>) -> ColorStop {
+    ColorStop { color, length }
+}
+
+fn literal(name: &str) -> Color {
+    Color::Literal(name.to_string())
+}
+
+#[test]
+fn color_string_round_trip() {
+    assert_eq!(color_to_string(&Color::Hex("abc".into())), "#abc");
+    assert_eq!(color_to_string(&literal("red")), "red");
+    assert_eq!(
+        color_to_string(&Color::Rgb(vec!["1".into(), "2".into(), "3".into()])),
+        "rgb(1,2,3)"
+    );
+    assert_eq!(
+        color_to_string(&Color::Rgba(vec!["1".into(), "2".into(), "3".into(), "0.5".into()])),
+        "rgba(1,2,3,0.5)"
+    );
+    assert_eq!(
+        color_to_string(&Color::Hsl(["120".into(), "50".into(), "50".into()])),
+        "hsl(120,50,50)"
+    );
+    assert_eq!(
+        color_to_string(&Color::Hsla(["120".into(), "50".into(), "50".into(), "0.5".into()])),
+        "hsla(120,50,50,0.5)"
+    );
+    assert_eq!(color_to_string(&Color::Var("--x".into())), "var(--x)");
+}
+
+#[test]
+fn evenly_distributed_stops() {
+    let stops = normalize_color_stops(
+        &[stop(literal("red"), None), stop(literal("blue"), None)],
+        100.0,
+    );
+    assert_eq!(stops[0].offset, 0.0);
+    assert_eq!(stops[1].offset, 1.0);
+
+    let stops = normalize_color_stops(
+        &[
+            stop(literal("a"), None),
+            stop(literal("b"), None),
+            stop(literal("c"), None),
+        ],
+        100.0,
+    );
+    assert_eq!(stops[1].offset, 0.5);
+}
+
+#[test]
+fn explicit_and_mixed_offsets() {
+    let stops = normalize_color_stops(
+        &[
+            stop(literal("red"), Some(Distance::Percent("20".into()))),
+            stop(literal("green"), None),
+            stop(literal("blue"), Some(Distance::Percent("80".into()))),
+        ],
+        100.0,
+    );
+    assert_eq!(stops[0].offset, 0.2);
+    assert_eq!(stops[1].offset, 0.5);
+    assert_eq!(stops[2].offset, 0.8);
+}
+
+#[test]
+fn px_and_em_offsets_use_gradient_length() {
+    let stops = normalize_color_stops(
+        &[
+            stop(literal("red"), Some(Distance::Px("50".into()))),
+            stop(literal("blue"), Some(Distance::Em("6.25".into()))),
+        ],
+        200.0,
+    );
+    assert_eq!(stops[0].offset, 0.25);
+    assert!((stops[1].offset - 0.5).abs() < 1e-9);
+}
+
+#[test]
+fn offsets_clamped() {
+    let stops = normalize_color_stops(
+        &[
+            stop(literal("red"), Some(Distance::Percent("-20".into()))),
+            stop(literal("blue"), Some(Distance::Percent("150".into()))),
+        ],
+        100.0,
+    );
+    assert_eq!(stops[0].offset, 0.0);
+    assert_eq!(stops[1].offset, 1.0);
+}
+
+#[test]
+fn leading_unpositioned_stops() {
+    let stops = normalize_color_stops(
+        &[
+            stop(literal("a"), None),
+            stop(literal("b"), None),
+            stop(literal("c"), Some(Distance::Percent("90".into()))),
+        ],
+        100.0,
+    );
+    assert_eq!(stops[0].offset, 0.0);
+    assert_eq!(stops[1].offset, 0.45);
+    assert_eq!(stops[2].offset, 0.9);
+}
+
+#[test]
+fn trailing_unpositioned_stops() {
+    let stops = normalize_color_stops(
+        &[
+            stop(literal("a"), Some(Distance::Percent("10".into()))),
+            stop(literal("b"), None),
+            stop(literal("c"), None),
+        ],
+        100.0,
+    );
+    assert_eq!(stops[0].offset, 0.1);
+    assert!((stops[1].offset - 0.55).abs() < 1e-9);
+    assert_eq!(stops[2].offset, 1.0);
+}
+
+#[test]
+fn transparent_stop_adopts_previous_color() {
+    let stops = normalize_color_stops(
+        &[
+            stop(Color::Hex("ff0000".into()), None),
+            stop(literal("transparent"), None),
+            stop(Color::Hex("0000ff".into()), None),
+        ],
+        100.0,
+    );
+    assert_eq!(stops[1].color, "rgba(255,0,0,0)");
+}
+
+#[test]
+fn transparent_stop_with_unparseable_donors_unchanged() {
+    let stops = normalize_color_stops(
+        &[
+            stop(literal("red"), None),
+            stop(literal("transparent"), None),
+            stop(literal("blue"), None),
+        ],
+        100.0,
+    );
+    assert_eq!(stops[1].color, "transparent");
+}
+
+#[test]
+fn transparent_stop_adopts_next_color_when_first() {
+    let stops = normalize_color_stops(
+        &[
+            stop(literal("transparent"), None),
+            stop(Color::Hex("00ff00".into()), None),
+        ],
+        100.0,
+    );
+    assert_eq!(stops[1].color, "#00ff00");
+    assert_eq!(stops[0].color, "rgba(0,255,0,0)");
+}
+
+#[test]
+fn all_transparent_stops_unchanged() {
+    let stops = normalize_color_stops(
+        &[
+            stop(literal("transparent"), None),
+            stop(Color::Rgba(vec!["0".into(), "0".into(), "0".into(), "0".into()]), None),
+        ],
+        100.0,
+    );
+    assert_eq!(stops[0].color, "transparent");
+    assert_eq!(stops[1].color, "rgba(0,0,0,0)");
+}