public void VerifyNullCommandThrows()
        {
            // Arrange
            var expectation = new WhiteSpaceStringBehaviorExpectation();

            // Act & Assert
            Assert.Throws <ArgumentNullException>(() => expectation.Verify(default));
        public void SutIsBehaviorExpectation()
        {
            // Arrange
            var expectation = new WhiteSpaceStringBehaviorExpectation();

            // Act & Assert
            Assert.IsAssignableFrom <IBehaviorExpectation>(expectation);
        }