How to Write Automated Tests with Postman

In this video Steve Griffith explains how to write automated API tests with Postman.

Automation Testing

Automation Testing is a technique that performs testing using special automated testing software tools to execute a test case suite. However, Manual Testing is performed by a human sitting in front of a computer carefully running the test steps.

Tests are automated by developing test suites. You can perform various types of automation testing using Postman, including unit tests, integration tests, functional tests, regression tests, end-to-end tests, mock tests, etc.

You need to select the software for automation, enter test data into the system under testing, compare expected and authentic results, and generate detailed test reports. Test Automation helps enhance the test coverage, effectiveness, and execution speed.

Why Automate your test APIs?

Although testing APIs can be complex but automating testing with your CI/CD Pipeline is easy. You can reuse your test suites through Postman to create a CI/CD pipeline. It would allow you to flawlessly integrate your Postman instance with Jenkins to generate your own CI/CD pipeline while creating bug-resistant programs by boosting test coverage and frequency. Run and manage your test workflow from The Postman app, Postman monitoring, or the command line with Newman.

Postman – Postman is a command-line tool used to develop your automated tests.

Why Postman?

It will help if you use Postman because:

  • You can enhance the scope of tests for better software quality using Postman.
  • It is essential for testing products with frequent releases and a large number of integrations.
  • You can automate test cases in JavaScript while writing test suites, building requests that contain dynamic parameters, and passing data between requests.
  • Postman validates APIs responses under test action, as defined in the test scripts.

POST Request Sample in Postman

It is a similar process as getting with some amendments in terms of the request body but based on service documentation, and you may have to add authorization, Headers, etc.

Integration Testing

API testing is also known as Integration testing. Integration testing focuses on verifying that the interactions of many small components can integrate without issue. Since API tests bypass the user interface, they tend to be quicker and more maintainable than GUI tests. Therefore, a good QA team will make reasonably accurate projections based on the backlog and general information about the project and its architecture and use automation for regression tests.

Schema Validation

To generate direct collections from the schema, write or use the API specification format of your choice in Postman, including RAML, OpenAPI, WADL, and GraphQL. Then, start versioning schemas in one central location. Don’t switch between the tools.

Creating and Debugging Tests Suits

You can produce custom test suites in JavaScript in the Postman Sandbox for each request. Use Postman’s PM API to establish more powerful tests that enable you to assert a set of predefined rules for cleaner testing. Insert variables in the request instances, and Postman will substitute them by choosing values from a data file or environment variable.

In your test suite, you can have several services ready for testing. This feature is available by using the New Collection shown in the image below from the left-hand panel of the Postman.

The Postman app uses the collection runner to test a collection and assess the results in real-time. Don’t run the same test by trying multiple instances of the same request with parameterization. If you face any issue, debug in the Postman’s Console Log, built mainly for API development, and records the raw requests, responses, certificates, and error logs from scripts.

Creation of Environment Variable

Every time you need to add the same URL to the manifold requests, only the user id is changed. So, in such cases, to allow reuse and to evade typos, you can generate variables by ticking this setting button on the right top corner.

Setting up the Environment

So here, you can first add up the environment and then one or more variables as per your need.

Creating/Updating Variables and Environment

You select the environment from the drop-down menu

Creating Test Cases

Follow the steps below:

  1. Click on the Tests tab.
  2. You can access the code snippets shown in the right-side panel and customize them as per your requirements.
  3. It demands basic knowledge of JSON.
  4. Press send and confirm the test results tab in the response section.

Collection Runner for Test Running

In your last step of automation testing, you use Collection Runner because you cannot manually test multiple scenarios. To do so, you click the highlighted button shown below and hit the Run button.

You can see the results in the collection runner.

Test Tool Selection

It is the most vital step in continuing with your automation testing, while Test Tool selection largely depends on the technology the “Application Under Test” is built on. For example, as QTP does not support Informatica, it cannot be used for testing the applications built on Informatica.

Automation Scope

The area of your application under testing is called the scope of automation. Scope of automation includes the crucial features for the business, standard functionalities across applications, scenarios with a large amount of data, and technical feasibility. It also contains the complexity of test cases, the extent to which business components are reused, and the ability to use the same test cases for cross-browser testing.

Automation Frameworks
Automation frameworks contain a set of automation guidelines that help maintain testing consistency, improve test structuring, normalize minimum usage of code, and enhance reusability.
Benefits of Automation Testing

70% faster than the manual testing
More comprehensive test coverage of application features
Saves Time and Cost
Reliable in results
Ensure Consistency
Re-usable test scripts
Improves accuracy
Test Frequently and thoroughlY
Increases Efficiency
Better speed in executing tests

In conclusion, Postman offers a comprehensive API testing tool that sets up automated tests. You can aggregate the tests and requests you have created into a single automated test sequence. Run and manage your test workflow from the Postman app, Postman monitoring, or command-line tool.

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