Not Constraint

NotConstraint negates another constraint. It succeeds when the inner constraint fails, and fails when the inner constraint succeeds.

Usage

Is.Not.<constraint>
Does.Not.<constraint>
Has.No.<constraint>

Examples

[Test]
public void NotConstraint_Examples()
{
    // Basic negation
    Assert.That(42, Is.Not.EqualTo(0));
    Assert.That("Hello", Is.Not.Null);
    Assert.That("Hello", Is.Not.Empty);

    // String negation
    Assert.That("Hello World", Does.Not.Contain("Goodbye"));
    Assert.That("test.txt", Does.Not.EndWith(".pdf"));

    // Collection negation
    Assert.That(new[] { 1, 2, 3 }, Has.No.Member(0));
    Assert.That(new[] { 1, 2, 3 }, Is.Not.Empty);
    Assert.That(new[] { 1, 2, 3 }, Has.None.Negative);

    // Type negation
    Assert.That("Hello", Is.Not.InstanceOf<int>());

    // Combined with And/Or
    object obj = 42;
    Assert.That(obj, Is.Not.Null.And.InstanceOf<int>());
    Assert.That("test", Is.Not.Null.And.Not.Empty);
}

Notes

  1. Is.Not, Does.Not, and Has.No are all ways to negate constraints.
  2. Has.No is specifically for collection constraints (equivalent to Has.None).
  3. Negation applies to the immediately following constraint.

See Also