MSTEST0019: Prefer TestInitialize methods over constructors

Cause

This rule raises a diagnostic when there is a parameterless explicit constructor declared on a test class (class marked with [TestClass]).

Rule description

To use one setup convention for synchronous and asynchronous tests, prefer [TestInitialize]. A constructor can't return an awaitable operation to MSTest, while the runner can await a Task or ValueTask returned by a test-initialization method before it starts the test.

Constructors are still supported for synchronous setup. This rule expresses an opt-in convention, not a runtime requirement. MSTEST0020 offers the alternative convention for constructor-based setup; don't enable both competing conventions.

How to fix violations

Move the setup from the parameterless constructor into a [TestInitialize] method.

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 MSTEST0019
// The code that's violating the rule is on this line.
#pragma warning restore MSTEST0019

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

[*.{cs,vb}]
dotnet_diagnostic.MSTEST0019.severity = none

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