public void TryGetFirstTest_Missing_Pass()
        {
            var dict = new BiDictionaryOneToOne <int, int> {
                { 0, 815 },
            };

            Assert.False(dict.TryGetFirst(888, out var unused));
        }
        public void TryGetFirstTest_Exists_Pass()
        {
            var dict = new BiDictionaryOneToOne <int, int> {
                { 0, 815 },
            };

            Assert.True(dict.TryGetFirst(815, out var first));
            Assert.Equal(0, first);
        }