NUnit1012

The async test method must have a non-void return type

Topic	Value
Id	NUnit1012
Severity	Error
Enabled	True
Category	Structure
Code	TestMethodUsageAnalyzer

Description

The async test method must have a non-void return type.

Motivation

To prevent tests that will fail at runtime due to improper construction.

How to fix violations

Example Violation

[Test]
public async void NUnit1012SampleTest()
{
    var result = await Task.FromResult(true);
    Assert.That(result, Is.True);
}

Explanation

async methods should generally not return void in C#. For example if an exception is thrown (as they are in the case of an assertion violation), the exception is actually a part of the task object. If the return type is void, no such object exists, to the exception is effectively swallowed.

Fix

Make the async test method return a Task:

[Test]
public async Task NUnit1012SampleTest()
{
    var result = await Task.FromResult(true);
    Assert.That(result, Is.True);
}

Or modify the test to not use async behavior:

[Test]
public void NUnit1012SampleTest()
{
    var result = true;
    Assert.That(result, Is.True);
}

Configure severity

Via ruleset file

Configure the severity per project, for more info see MSDN.

Via .editorconfig file

# NUnit1012: The async test method must have a non-void return type
dotnet_diagnostic.NUnit1012.severity = chosenSeverity

where chosenSeverity can be one of none, silent, suggestion, warning, or error.

Via #pragma directive

#pragma warning disable NUnit1012 // The async test method must have a non-void return type
Code violating the rule here
#pragma warning restore NUnit1012 // The async test method must have a non-void return type

Or put this at the top of the file to disable all instances.

#pragma warning disable NUnit1012 // The async test method must have a non-void return type

Via attribute [SuppressMessage]

[System.Diagnostics.CodeAnalysis.SuppressMessage("Structure",
    "NUnit1012:The async test method must have a non-void return type",
    Justification = "Reason...")]