Скачать или смотреть Resolving ILogger.LogLevel Issues in C# Unit Tests

Learn how to properly configure `ILogger` in your C# unit tests to ensure log levels are enabled, allowing for successful testing of your logging extensions.
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This video is based on the question https://stackoverflow.com/q/71514928/ asked by the user 'A I' ( https://stackoverflow.com/u/13222954/ ) and on the answer https://stackoverflow.com/a/71515136/ provided by the user 'Klaus Gütter' ( https://stackoverflow.com/u/2142950/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting ILogger.LogLevel Issues in C# Unit Tests

As developers delve into the world of unit testing, they often face various challenges related to logging frameworks. One common issue encountered is when using the ILogger interface from Microsoft.Extensions.Logging. Specifically, developers may find that logger.IsEnabled(logLevel) always returns false during unit tests, leading to unexpected test failures. This issue can be particularly frustrating when the exact same logging functionality works flawlessly outside of the test environment. In this guide, we'll explore why this problem occurs and how to effectively resolve it.

Understanding the Problem

In the provided scenario, a developer created an extension method for the ILogger interface that first checks whether a specific log level is enabled before attempting to log an error message. The extension method looks like this:

[[See Video to Reveal this Text or Code Snippet]]

The developer is facing issues with their unit test, where invoking the logging method leads to failure due to the IsEnabled check always returning false, regardless of the default log levels set in appsettings.json files for both their main project and the unit test project. As a result, when the check is in place, no logging occurs, leading to the unit test's failure.

Setting Up Your ILogger Mock Correctly

To resolve the issue with ILogger in your unit tests, you need to ensure that your mocked logger correctly simulates the expected behavior regarding log level checks. This involves setting up your mocked logger to return true for the desired log level before invoking any logging functionality.

Steps to Properly Enable Log Levels

Initialize the Mock: When creating your mock logger instance, you need to set it up to return true for the IsEnabled check corresponding to the log level you intend to test (in this case, LogLevel.Error).

Setup the Mock Behavior:
Make sure to configure the IsEnabled method to return true right after initializing your mock logger. Here’s how you can do this:

[[See Video to Reveal this Text or Code Snippet]]

Invoke the Extension Method: After setting up your logger properly, you can call the LogErrorExt method without it failing due to an incorrect log level check.

Example Test Code

Here's how your improved unit test class should look:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By correctly mocking the ILogger interface and ensuring that the necessary log level checks return true, you can effectively test your logging extension methods without unexpected failures. This simple setup allows you to build confidence in your logging approach through unit tests, ensuring that the logging behaves as intended both in development and production environments.

With these strategies in place, you can tackle potential logging-related issues in your unit tests with ease. Happy coding!