Collection Constraints (NUnit 2.4 / 2.5)
Collection constraints perform tests that are specific to collections. The following collection constraints are provided. Before NUnit 2.4.6, these constraints only operated on true Collections. Beginning with 2.4.6, they can work with any object that implements IEnumerable.
Beginning with NUnit 2.4.2, use of an improper argument type caused tests to fail. Later releases give an error rather than a failure, so that negated constraints will not appear to succeed.
For example, both of the following statements give an error in later releases, but the second would have succeeded in earlier versions of NUnit.
int[] iarray = new int[] { 1, 2, 3 };
Assert.That( 5, Is.SubsetOf( iarray ) ); // Fails in early releases
Assert.That( 5, Is.Not.SubsetOf( iarray ) ); /
AllItemsConstraint
Action
Applies a constraint to each item in a collection, succeeding only if all of them succeed.
Constructor
AllItemsConstraint(Constraint itemConstraint)
Syntax
Is.All... Has.All...
Examples of Use
int[] iarray = new int[] { 1, 2, 3 };
string[] sarray = new string[] { "a", "b", "c" };
Assert.That( iarray, Is.All.Not.Null );
Assert.That( sarray, Is.All.InstanceOf() );
Assert.That( iarray, Is.All.GreaterThan(0) );
Assert.That( iarray, Has.All.GreaterThan(0) );
SomeItemsConstraint
Action
Applies a constraint to each item in a collection, succeeding if at least one of them succeeds.
Constructor
SomeItemsConstraint(Constraint itemConstraint)
Syntax
Has.Some...
Examples of Use
int[] iarray = new int[] { 1, 2, 3 };
string[] sarray = new string[] { "a", "b", "c" };
Assert.That( iarray, Has.Some.GreaterThan(2) );
Assert.That( sarray, Has.Some.Length(1) );
NoItemConstraint
Action
Applies a constraint to each item in a collection, succeeding only if all of them fail.
Constructor
NoItemConstraint(Constraint itemConstraint)
Syntax
Has.None... Has.No...
Examples of Use
int[] iarray = new int[] { 1, 2, 3 };
string[] sarray = new string[] { "a", "b", "c" };
Assert.That( iarray, Has.None.Null );
Assert.That( iarray, Has.No.Null );
Assert.That( sarray, Has.None.EqualTo("d") );
Assert.That( iarray, Has.None.LessThan(0) );
UniqueItemsConstraint
Action
Tests that a collection contains only unique items.
Constructor
UniqueItemsConstraint()
Syntax
Is.Unique
Example of Use
string[] sarray = new string[] { "a", "b", "c" };
Assert.That( sarray, Is.Unique );
Notes
- ??
CollectionContainsConstraint
Action
Tests that a collection contains an object.
Constructor
CollectionContainsConstraint( object )
Syntax
Has.Member( object ) Contains.Item( object )
Examples of Use
int[] iarray = new int[] { 1, 2, 3 };
string[] sarray = new string[] { "a", "b", "c" };
Assert.That( iarray, Has.Member(3) );
Assert.That( sarray, Has.Member("b") );
Assert.That( sarray, Contains.Item("c") );
Assert.That( sarray, Has.No.Member("x") );
Notes
- For references, Has.Member uses object equality to find a member in a collection. To check for an object equal to an item the collection, use Has.Some.EqualTo(...).
CollectionEquivalentConstraint
Action
Tests that two collections are equivalent - that they contain the same items, in any order.
Constructor
CollectionEquivalentConstraint( IEnumerable other )
Syntax
Is.EquivalentTo( IEnumerable other )
Examples of Use
int[] iarray = new int[] { 1, 2, 3 };
string[] sarray = new string[] { "a", "b", "c" };
Assert.That( new string[] { "c", "a", "b" }, Is.EquivalentTo( sarray ) );
Assert.That( new int[] { 1, 2, 2 }, Is.Not.EquivalentTo( iarray ) );
Notes
- To compare collections for equality, use Is.EqualTo().
CollectionSubsetConstraint
Action
Tests that one collection is a subset of another.
Constructor
CollectionSubsetConstraint( ICollection )
Syntax
Is.SubsetOf( IEnumerable )
Example of Use
int[] iarray = new int[] { 1, 2, 3 };
Assert.That( new int[] { 1, 3 }, Is.SubsetOf( iarray ) );
CollectionOrderedConstraint (NUnit 2.5)
Action
Tests that a collection is ordered.
Constructor
CollectionOrderedConstraint()
Syntax
Is.Ordered
Modifiers
...Descending ...By(string propertyName) ...Using(IComparer comparer) ...Using(IComparer<T> comparer) ...Using (Comparison<T> comparer)
Examples of Use
int[] iarray = new int[] { 1, 2, 3 };
string[] sarray = new string[] { "c", "b", "a" };
string[] sarray2 = new string[] ( "a", "aa", "aaa" );
Assert.That( iarray, Is.Ordered );
Assert.That( sarray, Is.Ordered.Descending );
Assert.That( sarray2, Is.Ordered.By("Length");
Notes
- Modifiers may be combined and may appear in any order. If the same modifier is used more than once, the result is undefined.
- The syntax of Is.Ordered has changed from earlier betas.