InstanceOfType Constraint

InstanceOfTypeConstraint tests that an object is an instance of the specified type or any derived type. This is equivalent to the C# is operator.

Usage

Is.InstanceOf(Type expectedType)
Is.InstanceOf<T>()

Examples

[Test]
public void InstanceOfTypeConstraint_Examples()
{
    // Basic type checking
    Assert.That("Hello", Is.InstanceOf(typeof(string)));
    Assert.That("Hello", Is.InstanceOf<string>());
    Assert.That(42, Is.InstanceOf<int>());

    // Inheritance: derived types pass
    Assert.That("Hello", Is.InstanceOf<object>());         // string derives from object
    Assert.That(new List<int>(), Is.InstanceOf<IEnumerable<int>>());

    // Interface checking
    Assert.That(new List<int>(), Is.InstanceOf<IList<int>>());
    Assert.That(new Dictionary<string, int>(), Is.InstanceOf<IDictionary<string, int>>());

    // Negative tests
    Assert.That("Hello", Is.Not.InstanceOf<int>());
    Assert.That(null, Is.Not.InstanceOf<string>());        // null is not an instance of any type
}

Notes

  1. Is.InstanceOf<T>() is equivalent to C#'s value is T expression.
  2. For exact type matching (no inheritance), use ExactTypeConstraint.
  3. null always fails Is.InstanceOf for any type.

See Also