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MSTEST0001: Explicitly enable or disable tests parallelization

  • Article
Property Value
Rule ID MSTEST0001
Title Explicitly enable or disable tests parallelization
Category Performance
Fix is breaking or non-breaking Non-breaking
Enabled by default Yes
Default severity Info
Introduced in version 3.2.0

Cause

The assembly is not marked with [assembly: Parallelize] or [assembly: DoNotParallelize] attribute.

Rule description

By default, MSTest runs tests within the same assembly sequentially, which can lead to severe performance limitations. It is recommended to enable assembly attribute [assembly: Parallelize] to run tests in parallel, or if the assembly is known to not be parallelizable, to use explicitly the assembly level attribute [assembly: DoNotParallelize].

The default configuration of [assembly: Parallelize] is equivalent to [assembly: Parallelize(Scope = ExecutionScope.ClassLevel)], meaning that the parallelization will be set at class level (not method level) and will use as many threads as possible (depending on internal implementation).

How to fix violations

To fix a violation of this rule, add [assembly: Parallelize] or [assembly: DoNotParallelize] attribute. We recommend to use [assembly: Parallelize(Scope = ExecutionScope.MethodLevel)] to have best parallelization.

When to suppress warnings

Do not suppress a warning from this rule. Many libraries can benefit from a massive performance boost when enabling parallelization. When the test application is designed in a way that prevents parallelization, having the attribute explicitly set helps new developers to understand the limitations of the library.