public static void ContainsTest() { var r = Relations.Make <string, int>((s, i) => s.Length == i); Assert.True(r.Contains("", 0)); Assert.True(r.Contains("x", 1)); Assert.True(r.Contains("xyz", 3)); Assert.False(r.Contains("", 1)); Assert.False(r.Contains("x", 0)); Assert.False(r.Contains("x", -1)); Assert.False(r.Contains("xyz", 88)); }