TestingDataAnnotations.cs

public class RequiredIfAttributeTests
{
    [TestFixture]
    public class when_validating_required_if_attribute
    {
        private class TestModel
        {
            [RequiredIf("Property2", true)]
            public int? Property1 { get; set; }
            public bool Property2 { get; set; }
        }

        [Test]
        public void then_should_fail_model_validation_given_validation_property_null_and_target_property_value_equal_to_expected_value()
        {
            // Arrange
            var model = new TestModel { Property2 = true, Property1 = null };

            // Act
            var result = Validator.TryValidateObject(model, new ValidationContext(model, null, null), null, true);

            // Assert
            Assert.That(result, Is.False);
        }
        [Test]
        public void then_should_succeed_model_validation_given_validation_property_null_and_target_property_value_not_equal_to_expected_value()
        {
            // Arrange
            var model = new TestModel { Property2 = false, Property1 = null };

            // Act
            var result = Validator.TryValidateObject(model, new ValidationContext(model, null, null), null, true);

            // Assert
            Assert.That(result, Is.True);
        }

        [Test]
        public void then_should_fail_model_validation_given_validation_property_has_value_and_target_property_value_not_equal_to_expected_value()
        {
            // Arrange
            var model = new TestModel { Property2 = true, Property1 = 1 };

            // Act
            var result = Validator.TryValidateObject(model, new ValidationContext(model, null, null), null, true);

            // Assert
            Assert.That(result, Is.True);
        }

        [Test]
        public void then_should_succeed_model_validation_given_validation_property_has_value_and_target_property_value_equal_to_expected_value()
        {
            // Arrange
            var model = new TestModel { Property2 = true, Property1 = 1 };

            // Act
            var result = Validator.TryValidateObject(model, new ValidationContext(model, null, null), null, true);

            // Assert
            Assert.That(result, Is.True);
        }

    }
}