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MSTEST0003: Test methods should have valid layout

Property Value
Rule ID MSTEST0003
Title Test methods should have valid layout
Category Usage
Fix is breaking or non-breaking Breaking
Enabled by default Yes
Default severity Warning (escalated to Error when setting MSTestAnalysisMode to Recommended or All)
Introduced in version 3.2.0
Is there a code fix Yes

Cause

A test method doesn't follow the required test method layout.

Rule description

MSTest discovers methods marked with [TestMethod], creates a test-class instance, and invokes each method as a test. These requirements let the runner supply test data, observe failures, and complete the test lifecycle:

Requirement Reason
The method is public, or internal with [assembly: DiscoverInternals]. Public methods form MSTest's default test-entry-point contract. Internal discovery is an explicit alternative when you want tests to remain internal to the assembly. Private methods aren't test entry points.
The declaring type is accessible under the same discovery rules. A public method inside an inaccessible type isn't publicly accessible. MSTest checks the containing types as well as the method so discovery uses a consistent visibility contract.
The method isn't static. MSTest runs the method on the instance whose constructor, TestContext, TestInitialize, and TestCleanup belong to that test execution. Instance methods can use that per-test state instead of shared static state.
The method isn't abstract. The runner needs a method body to invoke. To share test implementations, declare concrete test methods in a base class and run them through concrete test classes.
The method isn't generic in MSTest 3.7 or earlier. In MSTest 3.8 and later, every type parameter can be inferred from the supplied test data. A generic method needs concrete type arguments before the runner can invoke it. Earlier versions don't infer those arguments. Later versions infer them from DataRow or DynamicData values, so a type parameter that doesn't occur in a method parameter can't be inferred.
The return type is void, Task, or ValueTask (ValueTask support starts with MSTest 3.3). MSTest uses assertions and exceptions to determine the outcome, not a returned value. Task and ValueTask let the runner wait for asynchronous work before it starts cleanup and records the result.
The method isn't async void. An async void method doesn't return an operation that MSTest can await. The runner can't reliably wait for its asynchronous work or associate later exceptions with the test result.
The method is an ordinary method, not a constructor, finalizer, accessor, or operator. Those special members have language-defined roles and invocation rules. An ordinary method provides an independent test entry point that MSTest can call with the test's arguments.

These requirements describe MSTest's discovery and invocation contract, not general C# or Visual Basic restrictions. For example, reflection can access non-public members, but MSTest deliberately uses the visibility rules above for test entry points.

How to fix violations

Ensure that the test method matches the required layout described above.

The MSTest analyzers can report signature problems in your editor, including in code inserted by IntelliSense. In Visual Studio, use the light bulb menu to apply an available code fix. A code fix helps correct the method; it doesn't change the editor's code-generation templates.

When to suppress warnings

Don't suppress a warning from this rule. An invalid signature can prevent test discovery or cause invocation to fail. Suppression hides the diagnostic but doesn't change how MSTest discovers or runs the method.

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 MSTEST0003
// The code that's violating the rule is on this line.
#pragma warning restore MSTEST0003

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

[*.{cs,vb}]
dotnet_diagnostic.MSTEST0003.severity = none

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

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