common/lru: add test case for BasicLRU.Peek (#27559)

common/lru/basiclru_test.go

@@ -170,6 +170,20 @@ func TestBasicLRUContains(t *testing.T) {
 	}
 }
 
+// Test that Peek doesn't update recent-ness
+func TestBasicLRUPeek(t *testing.T) {
+	cache := NewBasicLRU[int, int](2)
+	cache.Add(1, 1)
+	cache.Add(2, 2)
+	if v, ok := cache.Peek(1); !ok || v != 1 {
+		t.Errorf("1 should be set to 1")
+	}
+	cache.Add(3, 3)
+	if cache.Contains(1) {
+		t.Errorf("should not have updated recent-ness of 1")
+	}
+}
+
 func BenchmarkLRU(b *testing.B) {
 	var (
 		capacity = 1000