Add gif recording prototype

crates/egui_kittest/tests/recording.rs

@@ -0,0 +1,124 @@
+#![cfg(all(feature = "recording", feature = "wgpu"))]
+
+use egui_kittest::{Harness, RecordingOptions, RecordingTrigger};
+use kittest::Queryable as _;
+use tempfile::tempdir;
+
+fn counter_harness(value: &mut u32) -> Harness<'_, &mut u32> {
+    Harness::builder()
+        .with_size(egui::Vec2::new(120.0, 60.0))
+        .build_ui_state(
+            |ui, state| {
+                if ui.button(format!("count: {state}")).clicked() {
+                    **state += 1;
+                }
+            },
+            value,
+        )
+}
+
+fn count_pngs(dir: &std::path::Path) -> usize {
+    std::fs::read_dir(dir)
+        .expect("png output dir exists")
+        .filter_map(|e| e.ok())
+        .filter(|e| e.path().extension().and_then(|x| x.to_str()) == Some("png"))
+        .count()
+}
+
+#[test]
+fn records_gif_with_diffing() {
+    let dir = tempdir().expect("tempdir");
+    let gif_path = dir.path().join("counter.gif");
+
+    let mut value = 0u32;
+    let mut harness = counter_harness(&mut value);
+    harness.start_recording(RecordingOptions::gif(&gif_path, 12.0));
+
+    harness.run();
+    harness.run();
+    harness.get_by_label_contains("count").click();
+    harness.run();
+
+    assert!(harness.is_recording());
+    harness.finish_recording().expect("save gif");
+    assert!(!harness.is_recording());
+
+    let metadata = std::fs::metadata(&gif_path).expect("gif exists");
+    assert!(metadata.len() > 0, "GIF should be non-empty");
+}
+
+#[test]
+fn records_png_sequence() {
+    let dir = tempdir().expect("tempdir");
+    let out = dir.path().join("frames");
+
+    let mut value = 0u32;
+    let mut harness = counter_harness(&mut value);
+    harness.start_recording(
+        RecordingOptions::png_sequence(&out).with_trigger(RecordingTrigger::EveryStep),
+    );
+
+    harness.run();
+    harness.get_by_label_contains("count").click();
+    harness.run();
+
+    harness.finish_recording().expect("save png sequence");
+
+    assert!(count_pngs(&out) > 0, "expected at least one frame");
+}
+
+#[test]
+fn diff_every_step_dedupes_unchanged_frames() {
+    let dir = tempdir().expect("tempdir");
+    let out = dir.path().join("frames");
+
+    let mut value = 0u32;
+    let mut harness = counter_harness(&mut value);
+    harness.start_recording(
+        RecordingOptions::png_sequence(&out).with_trigger(RecordingTrigger::DiffEveryStep),
+    );
+
+    for _ in 0..6 {
+        harness.run();
+    }
+    harness.finish_recording().expect("save png sequence");
+
+    assert_eq!(
+        count_pngs(&out),
+        1,
+        "DiffEveryStep should dedupe unchanged frames"
+    );
+}
+
+#[test]
+fn on_run_trigger_captures_per_run_only() {
+    let dir = tempdir().expect("tempdir");
+    let out = dir.path().join("frames");
+
+    let mut value = 0u32;
+    let mut harness = counter_harness(&mut value);
+    harness.start_recording(
+        RecordingOptions::png_sequence(&out).with_trigger(RecordingTrigger::OnRun),
+    );
+
+    harness.run();
+    harness.get_by_label_contains("count").click();
+    harness.run();
+    harness.run();
+
+    harness.finish_recording().expect("save png sequence");
+
+    assert_eq!(
+        count_pngs(&out),
+        3,
+        "OnRun should produce one frame per run() call"
+    );
+}
+
+#[test]
+fn finish_recording_without_start_errors() {
+    let mut value = 0u32;
+    let mut harness = counter_harness(&mut value);
+    let err = harness.finish_recording().expect_err("not recording");
+    assert!(matches!(err, egui_kittest::RecordingError::NotRecording));
+}