A REST API test plan is a document that describes how to test the functionality, performance, security, and reliability of a RESTful web service. A REST API test plan can help you ensure that your API meets the expectations of your clients and users, and that it follows the best practices of REST architecture. In this article, we will explain how to create a REST API test plan in six steps.
The first step is to identify the API endpoints that you need to test. An endpoint is a URL that represents a resource or a collection of resources on the server. For example, /users, /products, or /orders. You can use tools like Postman, Swagger, or Insomnia to explore and document the available endpoints, along with their HTTP methods, parameters, headers, and responses.
A REST api is just a facade on top of code, which essentially is then just code. Consequently, the test plan is unit testing to code coverage. You’ll also need to do load testing, scalability, and security tests because an API has endpoints much like a client-based app. Unit Testing won’t tell you if you’ve captured the right user stories. Does the API provide the right data/services is driven by the user stories. Again, after that it’s just unit testing.
The next step is to define the test scenarios that you want to execute for each endpoint. A test scenario is a set of conditions and actions that simulate a user's interaction with the API. For example, creating a new user, updating a product, or deleting an order. You should consider both positive and negative scenarios, such as valid and invalid inputs, expected and unexpected outcomes, and error handling.
The third step in the process is to design test cases that implement the test scenarios. Each test case should have a unique identifier, a descriptive name, and a brief explanation of the test case objective. Additionally, you should assign a priority level to the test case and provide any relevant data that will be used as input. The test steps, expected result, actual result, and status of the test execution should also be included in the test case. Finally, any additional notes or observations should be documented in the test comments section.
The fourth step is to execute the test cases that you have designed. You can use tools like Postman, SoapUI, RestAssured, or JMeter to automate the execution of your test cases and generate reports. You can also use frameworks like Mocha, Jest, or PyTest to write and run your test cases as code. You should execute your test cases in different environments, such as development, staging, and production, and verify that the actual results match the expected results.
The fifth step is to analyze the test results that you have obtained from the execution of your test cases. You should identify and report any defects, errors, or failures that occurred during the testing process. You should also measure and evaluate the quality and performance of your API based on metrics such as response time, throughput, latency, availability, and reliability. You should use tools like Postman, SoapUI, RestAssured, or JMeter to generate and visualize the test results and metrics.
The final step is to update the test plan based on the feedback and changes that you have received from the analysis of the test results. You should review and revise your test scenarios, test cases, test data, and test steps to reflect the current state and requirements of your API. You should also document and communicate the test plan updates to your stakeholders and team members.
Don't forget to automate the tests and put them as a part of your CI/CD pipeline. APIs tend to be dependable enough so that other components rely on them, if your changes break the test case, consider creating a newer version of the endpoint.