1 files changed, 135 insertions, 0 deletions
diff --git a/src/ui/mru/tests.rs b/src/ui/mru/tests.rs
new file mode 100644
index 00000000..8e3d935f
--- /dev/null
+++ b/src/ui/mru/tests.rs
@@ -0,0 +1,135 @@
+use proptest::prelude::*;
+use proptest_derive::Arbitrary;
+
+use super::*;
+
+fn create_thumbnail() -> Thumbnail {
+    Thumbnail {
+        id: MappedId::next(),
+        timestamp: None,
+        on_current_output: false,
+        on_current_workspace: false,
+        app_id: None,
+        size: Size::new(100, 100),
+        clock: Clock::with_time(Duration::ZERO),
+        config: niri_config::MruPreviews::default(),
+        open_animation: None,
+        move_animation: None,
+        title_texture: Default::default(),
+        background: RefCell::new(FocusRing::new(Default::default())),
+        border: RefCell::new(FocusRing::new(Default::default())),
+    }
+}
+
+#[test]
+fn remove_last_window_out_of_two() {
+    let ops = [Op::Backward, Op::Remove(1)];
+
+    let thumbnails = vec![create_thumbnail(), create_thumbnail()];
+    let current_id = thumbnails.first().map(|t| t.id);
+    let mut mru = WindowMru {
+        thumbnails,
+        current_id,
+        scope: MruScope::All,
+        app_id_filter: None,
+    };
+
+    check_ops(&mut mru, &ops);
+}
+
+fn arbitrary_scope() -> impl Strategy<Value = MruScope> {
+    prop_oneof![
+        Just(MruScope::All),
+        Just(MruScope::Output),
+        Just(MruScope::Workspace),
+    ]
+}
+
+fn arbitrary_filter() -> impl Strategy<Value = MruFilter> {
+    prop_oneof![Just(MruFilter::All), Just(MruFilter::AppId)]
+}
+
+fn arbitrary_app_id() -> impl Strategy<Value = Option<String>> {
+    prop_oneof![Just(None), Just(Some(1)), Just(Some(2))]
+        .prop_map(|id| id.map(|id| format!("app-{id}")))
+}
+
+prop_compose! {
+    fn arbitrary_thumbnail()(
+        timestamp: Option<Duration>,
+        on_current_output: bool,
+        on_current_workspace: bool,
+        app_id in arbitrary_app_id(),
+    ) -> Thumbnail {
+        let mut thumbnail = create_thumbnail();
+        thumbnail.timestamp = timestamp;
+        thumbnail.on_current_workspace = on_current_workspace;
+        thumbnail.on_current_output = on_current_output;
+        thumbnail.app_id = app_id;
+        thumbnail
+    }
+}
+
+prop_compose! {
+    fn arbitrary_mru()(
+        thumbnails in proptest::collection::vec(arbitrary_thumbnail(), 1..10),
+    ) -> WindowMru {
+        let current_id = thumbnails.first().map(|t| t.id);
+        WindowMru {
+            thumbnails,
+            current_id,
+            scope: MruScope::All,
+            app_id_filter: None,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Arbitrary)]
+enum Op {
+    Forward,
+    Backward,
+    First,
+    Last,
+    SetScope(#[proptest(strategy = "arbitrary_scope()")] MruScope),
+    SetFilter(#[proptest(strategy = "arbitrary_filter()")] MruFilter),
+    Remove(#[proptest(strategy = "1..10usize")] usize),
+}
+
+impl Op {
+    fn apply(&self, mru: &mut WindowMru) {
+        match self {
+            Op::Forward => mru.forward(),
+            Op::Backward => mru.backward(),
+            Op::First => mru.first(),
+            Op::Last => mru.last(),
+            Op::SetScope(scope) => {
+                mru.set_scope(*scope);
+            }
+            Op::SetFilter(filter) => {
+                mru.set_filter(*filter);
+            }
+            Op::Remove(idx) => {
+                if *idx < mru.thumbnails.len() {
+                    mru.remove_by_idx(*idx);
+                }
+            }
+        }
+    }
+}
+
+fn check_ops(mru: &mut WindowMru, ops: &[Op]) {
+    for op in ops {
+        op.apply(mru);
+        mru.verify_invariants();
+    }
+}
+
+proptest! {
+    #[test]
+    fn random_operations_dont_panic(
+        mut mru in arbitrary_mru(),
+        ops: Vec<Op>,
+    ) {
+        check_ops(&mut mru, &ops);
+    }
+}