How to test code that interacts with external services in PHPUnit?

@dedrick 

To test code that interacts with external services in PHPUnit, you can use the following approaches:

1. Mocking: Mocking is the process of creating fake objects that mimic the behavior of real objects. In this case, you can create mock objects to simulate the external services and their responses. This allows you to control the behavior of the external services during testing, ensuring that the code being tested interacts correctly with them. PHPUnit provides built-in support for creating mock objects.
2. Dependency Injection: You can design your code in a way that allows you to inject different implementations of the external service dependencies. During testing, you can use a fake or stub implementation of the service that mimics the behavior without actually making any external calls. This helps isolate the code under test from the external services, making the tests faster and more reliable.
3. Environment Variables: If your code interacts with the external services using environment variables or configuration files, you can set up different values for these variables or files during testing. PHPUnit has support for environment variables, allowing you to define them in your test case and use different values for testing.
4. Integration Testing: In some cases, mocking or faking the external services might not be feasible or sufficient. In such cases, you can perform integration testing, where the code is tested against the actual external services. This approach requires making real requests to the external services, so it's important to have a well-defined test environment and proper test data. Integration tests can be slower and more complex to set up, but they provide confidence in the real-world behavior of the code.

Remember to use proper test isolation techniques, such as setting up and tearing down test data, to ensure that the tests are independent and repeatable.