MSTEST0068: Use Assert instead of CollectionAssert

Property	Value
Rule ID	MSTEST0068
Title	Use Assert instead of CollectionAssert
Category	Usage
Fix is breaking or non-breaking	Non-breaking
Enabled by default	Yes
Default severity	Info
Introduced in version	4.3.0
Is there a code fix	Yes

Note

This rule is available starting with MSTest 4.3.

Cause

A test method uses CollectionAssert methods instead of equivalent Assert methods.

Rule description

Most CollectionAssert methods have equivalent counterparts in Assert that provide the same functionality. Prefer the Assert methods for consistency, better readability, improved discoverability, and alignment with behavior across all test frameworks.

The following CollectionAssert methods have equivalent Assert methods:

• CollectionAssert.AreEqual(a, b) → Assert.AreSequenceEqual(a, b)
• CollectionAssert.AreNotEqual(a, b) → Assert.AreNotSequenceEqual(a, b)
• CollectionAssert.AreEquivalent(a, b) → Assert.AreSequenceEqual(a, b, SequenceOrder.InAnyOrder)
• CollectionAssert.AreNotEquivalent(a, b) → Assert.AreNotSequenceEqual(a, b, SequenceOrder.InAnyOrder)
• CollectionAssert.AllItemsAreNotNull(a) → Assert.AreAllNotNull(a)
• CollectionAssert.AllItemsAreUnique(a) → Assert.AreAllDistinct(a)
• CollectionAssert.AllItemsAreInstancesOfType(collection, typeof(T)) → Assert.AreAllOfType<T>(collection)
• CollectionAssert.Contains(collection, value) → Assert.Contains(value, collection)
• CollectionAssert.DoesNotContain(collection, value) → Assert.DoesNotContain(value, collection)

Warning

When migrating from CollectionAssert to Assert, be careful about the change in parameter order for Contains, DoesNotContain, and AllItemsAreInstancesOfType. In Assert, the expected value is always the first parameter.

Overloads of AreEqual/AreNotEqual that take an IComparer are skipped because Assert.AreSequenceEqual expects an IEqualityComparer<T> (different semantics). Overloads of AreEquivalent/AreNotEquivalent that take an IEqualityComparer<T> are also skipped. IsSubsetOf/IsNotSubsetOf have no direct Assert equivalent today and are not handled.

How to fix violations

Use the provided code fixer to automatically replace CollectionAssert method calls with their equivalent Assert methods. You can also manually replace the method calls if needed.

When to suppress warnings

Don't suppress warnings from this rule. The Assert methods provide the same functionality with better consistency.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

#pragma warning disable MSTEST0068
// The code that's violating the rule is on this line.
#pragma warning restore MSTEST0068

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

[*.{cs,vb}]
dotnet_diagnostic.MSTEST0068.severity = none

For more information, see How to suppress code analysis warnings.