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backend/internal/cache/bounded_lru_test.go

@@ -0,0 +1,57 @@
+package cache
+
+import "testing"
+
+func TestBoundedLRUEvictsLeastRecentlyUsed(t *testing.T) {
+	var evicted []string
+	cache := NewBoundedLRU[string, string](2, func(key, value string) {
+		evicted = append(evicted, key+"="+value)
+	})
+
+	if got := cache.GetOrAdd("a", func() string { return "A" }); got != "A" {
+		t.Fatalf("first value = %q, want A", got)
+	}
+	cache.GetOrAdd("b", func() string { return "B" })
+	if got, found := cache.Get("a"); !found || got != "A" {
+		t.Fatalf("Get(a) = %q/%t, want A/true", got, found)
+	}
+	cache.GetOrAdd("c", func() string { return "C" })
+
+	if _, found := cache.Get("b"); found {
+		t.Fatal("least recently used entry b was not evicted")
+	}
+	if got := cache.Len(); got != 2 {
+		t.Fatalf("Len() = %d, want 2", got)
+	}
+	if len(evicted) != 1 || evicted[0] != "b=B" {
+		t.Fatalf("evicted = %v, want [b=B]", evicted)
+	}
+}
+
+func TestBoundedLRUCreatesOneValuePerKeyConcurrently(t *testing.T) {
+	cache := NewBoundedLRU[string, int](2, nil)
+	started := make(chan struct{})
+	release := make(chan struct{})
+	results := make(chan int, 2)
+	creates := make(chan struct{}, 2)
+
+	create := func() int {
+		creates <- struct{}{}
+		close(started)
+		<-release
+		return 42
+	}
+	go func() { results <- cache.GetOrAdd("key", create) }()
+	<-started
+	go func() { results <- cache.GetOrAdd("key", func() int { creates <- struct{}{}; return 7 }) }()
+	close(release)
+
+	for range 2 {
+		if got := <-results; got != 42 {
+			t.Fatalf("cached value = %d, want 42", got)
+		}
+	}
+	if got := len(creates); got != 1 {
+		t.Fatalf("create calls = %d, want 1", got)
+	}
+}