Mastering Advanced Testing Techniques in Go
As a developer, you know that testing is crucial to ensuring the quality and reliability of your code. However, common testing methods may not be enough for complex projects. In this article, we’ll explore advanced testing techniques in Go that will help you write effective tests for any project.
Testing HTTP Handlers
Let’s start with a common scenario: testing HTTP handlers. To isolate elements for testing without impacting the rest of the code, HTTP handlers should be loosely coupled with their dependencies. If your HTTP handlers are well-designed initially, testing should be fairly straightforward.
Checking Status Code
Consider a basic test that checks the status code of an HTTP handler. For example, the index() handler should return a 200 OK response for every request. We can verify the handler’s response using the httptest package.
External Dependencies
Now, let’s consider another common scenario: our HTTP handler has a dependency on an external service. For instance, the getJoke handler expects an id query parameter, which it uses to fetch a joke from the Random dad joke API. To test this handler, we can use table-driven tests to test against a range of inputs.
Mocking in Go
However, making HTTP requests to the real API in our test is bad practice for unit testing code. Instead, we should mock the HTTP client. One way to do this is to create a custom interface that defines the methods used in the function and passes different implementations depending on where the function is called from.
Using External Data in Tests
In Go, you should place external data for tests in a directory called testdata. This approach allows you to store inputs that you want to test your program against. For example, let’s write a function that generates the base64 encoding from a binary file.
Using Golden Files
If you’re using a Go template, it’s a good idea to test the generated output against the expected output to confirm that the template is working as intended. Instead of hardcoding the expected output in the source code, we can use golden files. A golden file is a special type of file that contains the expected output of a test.
Conclusion
In this article, we’ve explored advanced testing techniques in Go, including mocking HTTP clients, using external data in tests, and creating golden files. By mastering these techniques, you’ll be able to write more effective tests for your projects and ensure the quality and reliability of your code.