CollectionAssert

The CollectionAssert class provides a number of methods that are useful when examining collections and their contents or for comparing two collections. These methods may be used with any object implementing IEnumerable.

The AreEqual overloads succeed if the corresponding elements of the two collections are equal. AreEquivalent tests whether the collection contents are equal, but without regard to order. In both cases, elements are compared using NUnit's default equality comparison.

CollectionAssert is in the NUnit.Framework namespace, so using NUnit.Framework; is enough. It ships in nunit.framework.legacy.dll, which is part of the NUnit package.

Note

In NUnit 4, CollectionAssert was in the NUnit.Framework.Legacy namespace and needed using NUnit.Framework.Legacy;.

CollectionAssert.AllItemsAreInstancesOfType(IEnumerable collection, Type expectedType);
CollectionAssert.AllItemsAreInstancesOfType(
    IEnumerable collection, Type expectedType, string message, params object[] args);

CollectionAssert.AllItemsAreNotNull(IEnumerable collection);
CollectionAssert.AllItemsAreNotNull(
    IEnumerable collection, string message, params object[] args);

CollectionAssert.AllItemsAreUnique(IEnumerable collection);
CollectionAssert.AllItemsAreUnique(
    IEnumerable collection, string message, params object[] args);

CollectionAssert.AreEqual(IEnumerable expected, IEnumerable actual);
CollectionAssert.AreEqual(
    IEnumerable expected, IEnumerable actual, string message, params object[] args);

CollectionAssert.AreEquivalent(IEnumerable expected, IEnumerable actual);
CollectionAssert.AreEquivalent(
    IEnumerable expected, IEnumerable actual, string message, params object[] args);

CollectionAssert.AreNotEqual(IEnumerable expected, IEnumerable actual);
CollectionAssert.AreNotEqual(
    IEnumerable expected, IEnumerable actual, string message, params object[] args);

CollectionAssert.AreNotEquivalent(IEnumerable expected, IEnumerable actual);
CollectionAssert.AreNotEquivalent(
    IEnumerable expected, IEnumerable actual, string message, params object[] args);

CollectionAssert.Contains(IEnumerable collection, object actual);
CollectionAssert.Contains(
    IEnumerable collection, object actual, string message, params object[] args);

CollectionAssert.DoesNotContain(IEnumerable collection, object actual);
CollectionAssert.DoesNotContain(
    IEnumerable collection, object actual, string message, params object[] args);

CollectionAssert.IsSubsetOf(IEnumerable subset, IEnumerable superset);
CollectionAssert.IsSubsetOf(
    IEnumerable subset, IEnumerable superset, string message, params object[] args);

CollectionAssert.IsNotSubsetOf(IEnumerable subset, IEnumerable superset);
CollectionAssert.IsNotSubsetOf(
    IEnumerable subset, IEnumerable superset, string message, params object[] args);

CollectionAssert.IsEmpty(IEnumerable collection);
CollectionAssert.IsEmpty(
    IEnumerable collection, string message, params object[] args);

CollectionAssert.IsNotEmpty(IEnumerable collection);
CollectionAssert.IsNotEmpty(
    IEnumerable collection, string message, params object[] args);

CollectionAssert.IsOrdered(IEnumerable collection);
CollectionAssert.IsOrdered(
    IEnumerable collection, string message, params object[] args);

CollectionAssert.IsOrdered(IEnumerable collection, IComparer comparer);
CollectionAssert.IsOrdered(IEnumerable collection,
    IComparer comparer, string message, params object[] args);

Contains and DoesNotContain

The parameters of Contains and DoesNotContain do not follow the usual expected, actual pattern of the other classic assertions. The first argument is the collection to search, and the second, named actual, is the single item being looked for. Despite its name, that item is what the assertion expects to find, so the failure message reports it on the Expected line and the collection on the But was line:

CollectionAssert.Contains(new[] { 1, 2 }, 3);

// Expected: some item equal to 3
//   But was:  < 1, 2 >

Passing a collection as the second argument does not check that one collection contains another. It checks whether the collection contains that collection as a single element. The parameter names are kept for compatibility, since renaming them would break callers that use named arguments. The constraint-based equivalents read more naturally:

Assert.That(new[] { 1, 2 }, Does.Contain(3));
Assert.That(new[] { 1, 2 }, Has.Member(3));

Examples

Comparing collections

[Test]
public void CollectionAssert_Basic_Examples()
{
    var list1 = new[] { 1, 2, 3 };
    var list2 = new[] { 1, 2, 3 };
    var list3 = new[] { 3, 2, 1 };
    var list4 = new[] { 1, 2, 4 };
    
    // Collections are equal (same order)
    CollectionAssert.AreEqual(list1, list2);
    
    // Collections are equivalent (same items, any order)
    CollectionAssert.AreEquivalent(list1, list3);
    
    // Collections are not equal
    CollectionAssert.AreNotEqual(list1, list4);
    
    // Collections are not equivalent
    CollectionAssert.AreNotEquivalent(list1, list4);
}

Testing for members

[Test]
public void CollectionAssert_Contains_Examples()
{
    var list = new[] { 1, 2, 3, 4, 5 };
    
    CollectionAssert.Contains(list, 3);
    CollectionAssert.DoesNotContain(list, 10);
}

Subsets

[Test]
public void CollectionAssert_Subset_Examples()
{
    var superset = new[] { 1, 2, 3, 4, 5 };
    var subset = new[] { 2, 4 };
    var notSubset = new[] { 1, 6 };
    
    CollectionAssert.IsSubsetOf(subset, superset);
    CollectionAssert.IsNotSubsetOf(notSubset, superset);
}

Empty collections

[Test]
public void CollectionAssert_Empty_Examples()
{
    var emptyList = new int[] { };
    var nonEmptyList = new[] { 1, 2, 3 };
    
    CollectionAssert.IsEmpty(emptyList);
    CollectionAssert.IsNotEmpty(nonEmptyList);
}

Ordering

[Test]
public void CollectionAssert_Ordered_Examples()
{
    var orderedList = new[] { 1, 2, 3, 4, 5 };
    var reverseOrderedList = new[] { 5, 4, 3, 2, 1 };
    
    CollectionAssert.IsOrdered(orderedList);
    CollectionAssert.IsOrdered(reverseOrderedList, Comparer<int>.Create((x, y) => y.CompareTo(x)));
}

Item types

[Test]
public void CollectionAssert_ItemType_Examples()
{
    var stringList = new[] { "a", "b", "c" };
    var mixedList = new object[] { "string", 123, null };
    
    CollectionAssert.AllItemsAreInstancesOfType(stringList, typeof(string));
    CollectionAssert.AllItemsAreNotNull(stringList);
    CollectionAssert.AllItemsAreUnique(stringList);
}

See Also

• Collection Constraints