Stubbing HTTP requests
It is common for the Node.js applications you’re building to rely on and consume an external service or API. When unit testing, you do not typically want your test to send a request to an external service. Requests to the external service you’re consuming are metered or rate-limited, and you do not want your test cases to consume the allowance.
It’s also possible that your tests would require access to service credentials. This means every developer on the project would need access to those credentials before they could run the test suite.
To be able to unit test your code without sending a request to an external service, you can fake a request and response. This concept is known as stubbing. Stubbing can be used to mimic API calls, without sending the request. Stubbing comes with the additional benefit of reducing any request latency, potentially making the tests run faster than if they were to send real requests.
The test concepts...
