Best API Testing Tools

Some of the main reasons API testing is done:

• To make sure the API does what it’s supposed to do.
• To make sure it can handle the load.
• Because ensuring that all data access goes only through the API significantly simplifies security and compliance testing and thereby certification, since there is only one interface.
• To find all the way users can mess things up.
• To make sure your APIs work across devices, browsers, and operating systems.
• Because it can be costly not to.
• To make sure that the API offers complete functionality for easy future expansion of the application as new business needs arise.

API testing can reveal:

• Unused flags.
• Missing or duplicate functionality.
• Reliability issues.
• That response data is not structured correctly (JSON or XML).
• Difficulty in connecting and getting a response from the API.
• Security issues.
• That the API fails to handle error conditions gracefully.
• Multi-threading issues.
• Performance issues.
• Improper errors/warning to a caller.
• Incorrect handling of valid argument values.

The different types of API testing include:

• Functionality testing ensures that the API works and does exactly what it’s supposed to do.
  
  
• Reliability testing makes sure that the API can be consistently connected to and leads to consistent results.
  
  
• Load testing is performed to make sure the API can handle a large amount of calls.
  
  
• Creativity testing is conducted to ensure the API can handle being used in different ways.
  
  
• Security testing is used so that the API has defined security requirements, including authentication, permissions, and access controls.
  
  
• Proficiency testing is done to test that the API increases what developers are able to do.
  
  
• API documentation testing, also called discovery testing, is where the API documentation easily guides the user.
  
  
• Negative testing entails checking for every kind of wrong input the user can possibly supply.

If you are going to conduct API testing manually, you will need to have coding knowledge. However, if you will be doing API testing through automation, code will be unnecessary. Automated testing is highly recommended for API testing.

API testing can be one of the most challenging parts of software and QA testing. In order to learn it, begin by understanding API requirements. Once you have familiarized yourself with those, specify the API output status, focus on small, functional APIs, and organize API endpoints. Then, leverage automation capability for API testing and choose a suitable automation tool.

When conducting API testing, here are some helpful tips:

• Test for the typical or expected results first.
  
• For complete test coverage, create test cases for all possible API input combinations.
• Automate wherever you can.
• Avoid “test chaining” in your development.
• Add stress to the system through a series of API load tests.
• Group test cases by test category.
• Test for failure.
• On top of each test, you should include the declarations of the APIs being called.
• See how the API handles unforeseen problems and loads.
• Perform well-planned call sequencing.
• Limit the tests from as many variables as possible by keeping the API as isolated as possible.
• create API test cases for all possible input combinations of the API.
• Prioritize API function calls so that it will be easy for testers to test quickly and easily.

Valuable API testing tools include:

• Easy-to-use UI
• Able to run on Mac, Linux, Windows
• Supports REST, SOAP requests, and SSL client certificates
• Native CI/CD integrations (Jenkins, Azure DevOps, CircleCI, Dockers, etc.)
• Data-driven testing methods
• Better test coverage and reliability
• Built-in reporting platform to centralize reports and activities across tool stacks
• Many integrations, like support for Swagger & RAML formats
• Run, test, document, and monitoring features
• API traffic, error rate, and response time tracking
• Cache and offline replay of test results
• Compatibility with CSV files
• Supports configuration switching/staging, multithreaded parallel execution

API testing tools have many benefits, including:

• Better test coverage: Most API/web services have specifications, allowing you to create automated tests with high coverage, including functional testing and non-functional testing.

• Faster releases: Compared to UI testing, executing API testing saves up to eight hours, allowing software development teams to release products faster.

• GUI-independent: API testing can be performed in the app prior to GUI testing. When you do early testing, you can gain early feedback, which ultimately results in better team productivity.

• Language-independent: With API testing tools, data is exchanged via XML and JSON formats, so any language can be used for test automation, which makes it easy for QA teams to choose the language of their choice.

• Time-efficient: Because API testing doesn't require a GUI to be ready, it can be performed early on in the development cycle. Test results are provided very quickly, and thus significantly accelerate development workflows, helping you speed up the feedback loop and catch issues faster.

• Reduced costs: API tests' increased execution speed leads to more effective resource consumption, and therefore lower overall testing costs.

• Greater test stability: API interfaces are very much stable. APIs are very stable and usually include detailed documentation. Because API interfaces have good stability, it makes it easier for QA engineers to adjust their test suites in a timely fashion. And due to this inherent stability, API tests are also much easier to maintain.

• Improved test coverage: API-level tests are specifically designed to verify that all system components function as intended. API testing helps uncover potential defects in the interfaces, servers, and databases, improving the overall software quality and contributing to better user experiences.