public void ConstructorShouldInitializeFromSequence()
        {
            // arrange
            var expected = new[] { "1", "2", "3" };

            // act
            var target = new ObservableStack<string>( expected );

            // assert
            Assert.Equal( 3, target.Count );
            Assert.True( target.SequenceEqual( expected.Reverse() ) );
        }