NoItem Constraint

NoItemConstraint applies a constraint to each item in an IEnumerable, succeeding only if no items satisfy the constraint. An exception is thrown if the actual value does not implement IEnumerable.

Usage

Has.None.<constraint>

Examples

[Test]
public void NoItemConstraint_Examples()
{
    int[] numbers = { 1, 2, 3, 4, 5 };
    string[] names = { "Alice", "Bob", "Carol" };

    // No items should satisfy the constraint
    Assert.That(numbers, Has.None.LessThan(0));         // No negatives
    Assert.That(numbers, Has.None.GreaterThan(100));    // None > 100
    Assert.That(names, Has.None.Null);                  // No nulls
    Assert.That(names, Has.None.Empty);                 // No empty strings
    Assert.That(names, Has.None.EqualTo("Dave"));       // "Dave" not in list

    // Property-based constraints
    Assert.That(names, Has.None.Length.GreaterThan(10)); // No name > 10 chars

    // Multiple conditions
    Assert.That(numbers, Has.None.LessThanOrEqualTo(0));
}

Notes

  1. Has.None is the inverse of Has.Some - the constraint passes if no items match.
  2. The constraint fails as soon as the first matching item is found.
  3. An empty collection satisfies Has.None for any constraint.

See Also