Property Constraint

PropertyConstraint tests the value of a named property on an object against a further constraint.

Usage

Has.Property(string propertyName).<constraint>
Has.Length.<constraint>
Has.Count.<constraint>
Has.Message.<constraint>
Has.InnerException.<constraint>

Examples

public class Person
{
    public string Name { get; set; } = "";
    public int Age { get; set; }
}

[Test]
public void PropertyConstraint_Examples()
{
    // Test property values
    Assert.That("Hello", Has.Property("Length").EqualTo(5));
    Assert.That(new int[] { 1, 2, 3 }, Has.Property("Length").EqualTo(3));

    // Common properties have shortcuts
    Assert.That("Hello", Has.Length.EqualTo(5));
    Assert.That(new List<int> { 1, 2, 3 }, Has.Count.EqualTo(3));

    // Exception properties
    var ex = new InvalidOperationException("Test error", new ArgumentException());
    Assert.That(ex, Has.Message.EqualTo("Test error"));
    Assert.That(ex, Has.InnerException.InstanceOf<ArgumentException>());

    // Custom object properties
    var person = new Person { Name = "Alice", Age = 30 };
    Assert.That(person, Has.Property("Name").EqualTo("Alice"));
    Assert.That(person, Has.Property("Age").GreaterThan(18));
}

Built-in Property Shortcuts

Has.Length       // Equivalent to Has.Property("Length")
Has.Count        // Equivalent to Has.Property("Count")
Has.Message      // Equivalent to Has.Property("Message")
Has.InnerException // Equivalent to Has.Property("InnerException")

Notes

  1. If no constraint follows Has.Property(), it becomes a PropertyExistsConstraint.
  2. The property must be public and readable.
  3. If the property doesn't exist, the constraint fails with a descriptive message.

See Also