Setting Up Your Testing Environment
Before writing tests, set up a dedicated test project for your application.
Here's how to get started:
1. Create a Test Project
Add a new test project to your solution using Visual Studio or .NET CLI.
2. Install Required Packages
Install the following NuGet packages in your test project:
- xUnit for writing tests.
- xUnit.runner.visualstudio for running tests in Visual Studio.
- Microsoft.NET.Test.Sdk for test discovery.
- NSubstitute for mocking dependencies.
Use the following commands:
3. Include ASP.NET Core Dependencies
If your filters interact with ASP.NET Core components (e.g., controllers, HTTP context), install Microsoft.AspNetCore.Mvc.
Example 1: Testing a Query String Modifier Filter#
Filter Code
This filter modifies query string parameters before an action is executed:
Writing the Test
This test ensures the filter correctly modifies the query string:
Key Points in Testing
- Setup: Mocking the necessary context, like HttpContext and ActionExecutingContext.
- Execution: Simulating the execution of the filter by calling OnActionExecutionAsync.
- Assertion: Checking the modified query string to confirm the filter's behavior.
Example 2: Testing an Audit Logging Filter#
Filter Code
This filter logs how long an action takes to execute:
Writing the Test
Here, we focus on verifying that the filter logs the correct information after action execution.
Key Points in Testing
- Logger Mocking: Using NSubstitute to mock the ILogger dependency.
- Async Behavior: Ensuring the asynchronous nature of the filter is handled correctly in the test.
- Log Verification: Checking that the correct log messages are being generated.
Best Practices for Testing Action Filters#
- Mock Dependencies: Use libraries like NSubstitute to mock services, ensuring your tests focus on the filter's logic.
- Isolate Tests: Test each filter independently without external interference.
- Test Both Success and Failure Scenarios: Verify how the filter behaves in all possible cases.
Conclusion#
Action Filters are an essential part of ASP.NET Core applications, but their complexity means they need robust testing.
Using xUnit, you can ensure your filters work as intended, minimizing bugs and improving application quality.
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