MSTEST0020: Prefer constructors over TestInitialize methods

Cause

This rule raises a diagnostic when there is a void [TestInitialize] method.

Rule description

For synchronous setup, a constructor lets you assign readonly fields and lets the compiler check that non-nullable members are initialized before construction completes. The compiler doesn't know that MSTest will call a later [TestInitialize] method, so setup there doesn't provide the same constructor-initialization guarantees.

[TestInitialize] is still supported and is appropriate for asynchronous setup. This rule expresses an opt-in convention, not a runtime requirement. MSTEST0019 offers the alternative convention for test-initialization methods; don't enable both competing conventions.

How to fix violations

Replace [TestInitialize] returning void by constructors.

When to suppress warnings

You usually don't want to suppress warnings from this rule if you decided to opt-in for it.

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 MSTEST0020
// The code that's violating the rule is on this line.
#pragma warning restore MSTEST0020

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

[*.{cs,vb}]
dotnet_diagnostic.MSTEST0020.severity = none

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