SparkyTestHelpers: DataAnnotations

NuGet package | Source code | API documentation

This NuGet package contains helper classes to enable unit testing of .NET models and entities that use System.ComponentModel.DataAnnotations ValidationAttributes and/or validation via IValidatableObject.Validate(), via a fluent syntax.

Validation is initialized via the static Validation.For(obj) method:

using SparkyTestHelpers.DataAnnotation;
. . .
    var foo = new Foo { /* populated with valid values */ };
    ValidationForModel<Foo> validation = Validation.For(foo);

The .ValidationResults() method validates the object and returns the results:

IEnumerable<ValidationResult> validationResults = Validation.For(foo).ValidationResults();

…but you’ll usually check validation results via other fluently-composed methods:

Validation.For(foo).ShouldReturn.NoErrors();

The When(expression) method arranges entity adjustments to be tested. (It makes a “clone” of the instance passed to Validation.For() before making adjustments, so each “When” call starts fresh with the original values):

Validation.For(foo)
    .When(x => x.Bar = null)
    .ShouldReturn.RequiredErrorFor(x => x.Bar);

A code example above shows a call to .ShouldReturn.NoErrors() to assert that the model has no validation errors.

.ShouldReturn.ErrorFor() is used to assert that a specific validation error was returned:

Validation.For(foo)
    .When(x => x.Bar = "13")
    .ShouldReturn.ErrorFor(x => x.Bar)
    .WithMessage("Invalid Bar value. 13 is unlucky!");

// Multi-member validation result:
Validation.For(foo)
    .When(x => 
    { 
        x.Bar = "dog";
        x.Baz = "cat";
    })
    .ShouldReturn.ErrorFor(x => x.Bar).AndFor(x => x.Baz)
        .WithMessage("Invalid Bar/Baz combination.");

ShouldReturn.ErrrorFor(expression).ForValidationAttribute<TAttribute> is used to assert that a ValidationResult was created by a specific ValidationAttribute:

Validation.For(foo)
    .When(x => x.Bar = null)
    .ShouldReturn.ErrorFor(x => x.Bar).ForValidationAttribute<RequiredAttribute>();

There are also ShouldReturn. methods for standard ValidationAttributes:

• [CreditCard]: ShouldReturn.CreditCardErrorFor(x => x.Foo);
• [EmailAddress]: ShouldReturn.EmailAddressErrorFor(x => x.Foo);
• [EnumDataType]: ShouldReturn.EnumDataTypeErrorFor(x => x.Foo);
• [MaxLength]: ShouldReturn.MaxLengthErrorFor(x => x.Foo);
• [MinLength]: ShouldReturn.MinLengthErrorFor(x => x.Foo);
• [Phone]: ShouldReturn.PhoneErrorFor(x => x.Foo);
• [Range]: ShouldReturn.RangeErrorFor(x => x.Foo);
• [RegularExpression]: ShouldReturn.RegularExpressionErrorFor(x => x.Foo);
• [Required]: ShouldReturn.RequiredErrorFor(x => x.Foo);
• [StringLength]: ShouldReturn.StringLengthErrorFor(x => x.Foo);

You don’t have to specify the expected error message for the .ForValidationAttribute method or for the methods listed above. The validation tester automatically determines the error message from the attribute.

Happy Testing!