MSTEST0024: Do not store TestContext in a static member

Cause

This rule raises a diagnostic when an assignment to a static member of a TestContext parameter is done.

Starting with MSTest 4.4, the rule also detects coalescing assignments, such as s_testContext ??= testContext, and deconstruction assignments that store TestContext in a static member.

Rule description

The TestContext passed to [AssemblyInitialize] or [ClassInitialize] describes that fixture's lifecycle, not the currently executing test. MSTest doesn't update a cached fixture context to turn it into the context for each later test.

For example, TestName and data-row properties belong to per-test execution and aren't available in class or assembly fixtures. A saved fixture context can't supply those values for the current test. Static caching also encourages concurrent tests to share a context that isn't theirs. To access per-test information, use the test instance's TestContext; share specific fixture data instead of the context object.

How to fix violations

Do not store the [AssemblyInitialize] or [ClassInitialize] TestContext parameter.

When to suppress warnings

You can suppress warnings from this rule if you are sure of the behavior does match what you want to do.

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 MSTEST0024
// The code that's violating the rule is on this line.
#pragma warning restore MSTEST0024

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

[*.{cs,vb}]
dotnet_diagnostic.MSTEST0024.severity = none

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