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.

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Happy Testing!