1 files changed, 111 insertions, 0 deletions
diff --git a/rust/crates/timeline/tests/retime.rs b/rust/crates/timeline/tests/retime.rs
new file mode 100644
index 00000000..b495fec6
--- /dev/null
+++ b/rust/crates/timeline/tests/retime.rs
@@ -0,0 +1,111 @@
+use scene::RetimeConfig;
+use timeline::retime::{
+    clamp_retime_rate, get_clip_time_at_source_time, get_effective_rate_at,
+    get_source_span_at_clip_time, get_source_time_at_clip_time,
+    get_timeline_duration_for_source_span, split_retime_at_clip_time,
+};
+
+const TWO_X: RetimeConfig = RetimeConfig {
+    rate: 2.0,
+    maintain_pitch: None,
+};
+const HALF_X: RetimeConfig = RetimeConfig {
+    rate: 0.5,
+    maintain_pitch: None,
+};
+
+#[test]
+fn maps_clip_time_to_source_time_at_2x_speed() {
+    assert_eq!(get_source_time_at_clip_time(5.0, Some(&TWO_X)), 10.0);
+}
+
+#[test]
+fn maps_clip_time_to_source_time_at_half_speed() {
+    assert_eq!(get_source_time_at_clip_time(4.0, Some(&HALF_X)), 2.0);
+}
+
+#[test]
+fn returns_clip_time_unchanged_when_no_retime() {
+    assert_eq!(get_source_time_at_clip_time(7.0, None), 7.0);
+}
+
+#[test]
+fn inverts_source_time_back_to_clip_time_at_2x_speed() {
+    assert_eq!(get_clip_time_at_source_time(10.0, Some(&TWO_X)), 5.0);
+}
+
+#[test]
+fn returns_effective_rate() {
+    assert_eq!(get_effective_rate_at(Some(&TWO_X)), 2.0);
+    assert_eq!(get_effective_rate_at(None), 1.0);
+}
+
+#[test]
+fn derives_timeline_duration_for_a_visible_source_span() {
+    assert_eq!(
+        get_timeline_duration_for_source_span(10.0, Some(&TWO_X)),
+        5.0
+    );
+    assert_eq!(
+        get_timeline_duration_for_source_span(10.0, Some(&HALF_X)),
+        20.0
+    );
+}
+
+#[test]
+fn clamps_invalid_rates_to_one() {
+    let zero = RetimeConfig {
+        rate: 0.0,
+        maintain_pitch: None,
+    };
+    let negative = RetimeConfig {
+        rate: -1.0,
+        maintain_pitch: None,
+    };
+    assert_eq!(get_source_time_at_clip_time(5.0, Some(&zero)), 5.0);
+    assert_eq!(get_source_time_at_clip_time(5.0, Some(&negative)), 5.0);
+    assert_eq!(clamp_retime_rate(f64::NAN), 1.0);
+    assert_eq!(clamp_retime_rate(f64::INFINITY), 1.0);
+}
+
+#[test]
+fn caps_retime_rates_above_5x() {
+    let hundred = RetimeConfig {
+        rate: 100.0,
+        maintain_pitch: None,
+    };
+    assert_eq!(get_source_time_at_clip_time(5.0, Some(&hundred)), 25.0);
+    assert_eq!(
+        get_timeline_duration_for_source_span(10.0, Some(&hundred)),
+        2.0
+    );
+}
+
+#[test]
+fn measures_source_span_at_a_clip_time() {
+    assert_eq!(get_source_span_at_clip_time(5.0, Some(&TWO_X)), 10.0);
+}
+
+#[test]
+fn returns_zero_for_non_positive_clip_time() {
+    assert_eq!(get_source_span_at_clip_time(0.0, None), 0.0);
+    assert_eq!(get_source_span_at_clip_time(-1.0, None), 0.0);
+}
+
+#[test]
+fn passes_the_same_retime_to_both_halves_when_splitting() {
+    let retime = RetimeConfig {
+        rate: 1.5,
+        maintain_pitch: None,
+    };
+    let (left, right) = split_retime_at_clip_time(Some(&retime));
+    assert_eq!(left, Some(retime));
+    assert_eq!(right, Some(retime));
+}
+
+#[test]
+fn returns_none_on_both_sides_when_no_retime() {
+    let (left, right) = split_retime_at_clip_time(None);
+    assert_eq!(left, None);
+    assert_eq!(right, None);
+}