Application Programming Interfaces (APIs) help software development teams to easily connect and engage in end-to-end business processes. APIs are the key to web apps & services. However, these end-to-end processes can only be as high-performing as the APIs they depend on.
Building automated tests for API and QA pipelines for web services is tough. Of the most prominent issues, automated end-to-end API Functional Testing and acceptance testing techniques face are:
I. Unreliable and flaky tests
II. Hard to isolate and identify large systems errors
III. Slow turnaround time for bug fixes
IV. Setup and tear down steps can leave leftover test data which can alter future tests and production systems.
To overcome these issues, here are a few must-follow API Test Automation practices when it comes to testing Application Programming Interfaces upfront:
1- Do Not Repeat Yourself
Before adding tests, make sure to create a client for your system under test.
Avoid repeating the code, but many tests require addressing the same components or similar actions. In such cases, you might want to create a common library to wrap the test requests and make their usage shorter and the process as simpler as possible.
2- Clarity
Write clear tests that easily allow debugging.
When tests are running successfully, they hardly require any attention or time. When the same tests start failing, resources need to be allocated to find the cause of failure. This process is time-consuming during product development and can go as far as pushing deadlines or cutting new features from your product in place.
Here are a few reasons your tests fail –
- Flaw and instability in automated test
- Environment failure or environment limitation
- Changes to the product without marking changes to test
- Flaw and instability in functionality
To save resources and optimize the process as much as possible, debugging should be a priority while you create the test.
- Each ‘System under Test’ component needs to be tested separately for each possible configuration.
- All the additional information like descriptors, ids; should be included in the report to make it more informative.
- Any failure of the test should be clear in the report. Moreover, the results of any failure must be saved and accessible in the system so that data can be traced back.
3- Performance
Always keep tabs on API performance functionality using API tests. These tests can be set up to monitor availability and speed issues, and the data collected over time can be used to analyze the performance trends.
Although testing just the availability is not enough, most API transactions involve data exchange, so it becomes quite necessary to ensure that the data is reliable. You can also test if the APIs are functioning correctly by validating the inputs and ensuring their data is structured in the correct format.
Test functionality of new deployments to catch issues before real-time users are impacted -when rolling out new features as part of a release, it is important to measure the impact on existing API integrations. The application might slow down drastically or at times even crash if the changes in the application do not work with the APIs you use.
Continuously testing API endpoints to ensure availability — monitoring API endpoints help you to identify outages or performance issues quickly. This minimizes the impact on end-users.
Test all of the application API dependencies to make sure performance is not degraded. When you have multiple APIs built into an application or provide APIs that integrate with applications using multiple APIs, it is recommended that you test the API dependencies frequently since they are constantly upgraded and updated.
4- Treat the API you’re Testing Like a Consumer Would
If you’re testing an API, you need to treat it exactly as a consumer would. At times, while writing test suites we focus too much on what we know to be the proper response. To properly examine all our API endpoints, we need to introduce the sort of errors that a user might introduce knowingly or unknowingly. In other words, we need to think like a user. After all, things rarely break in predictable ways in a live environment so it’s really important to test like we’re already there.
5- Eliminate as Many Fixed Data Sources as Possible
API endpoints often rely on the output from other APIs, when in a live environment. The only way to ensure that this is intact is to create an integration test which calls the first API and then uses the result of that call to hit the second API. When we begin testing the second API with collected static expected data from the first API, we are no longer testing the environment holistically. We should follow actual user flows and create integration tests rather than testing individual endpoints in thin air, wherever possible.
6- Other Factors That Need To Be Taken Care Of
A tester must have –
Parameters:
- List of all required parameters in JSON request
- List of all mandatory params in JSON request
Connections:
When it comes to Performance testing you need to check-
a) The number of concurrent connections a server can take before it fails.
b) Concurrent loads in batches like 25, 100, 200, and 500.
c) The expected response time and the expected throughput for all user loads.
d) The expected queries executed per second
7- Structuring tests
An API consists of several methods and operations which can be tested individually as well as through a setup of test scenarios. These test scenarios are usually constructed by combining multiple API calls.
Here are some approaches to test any API:
- Perform syntax testing of individual methods and operations wherever possible
This is performed to check whether a method or operation accepts correct input and rejects incorrect input. For instance:
I. Syntax testing determines if leaving mandatory fields empty results in an error
II. Optional fields are easily accepted as expected
III. Filling fields with incorrect data types should result in an error
- Perform functional testing of individual methods and operations wherever possible
This type of testing is performed to check whether the method and operations perform their intended action correctly. For instance:
I. Check whether calculation A is performed correctly when calling operation or method B with parameters X, Y, and Z.
II. Check whether data is stored correctly for future use when calling a setter method.
III. Check whether calling a getter method retrieves the correct required information.
- Construct and execute a decent amount of test scenarios
When individual methods and operations have been tested successfully, method calls can be bound together to emulate business processes.
8- API virtualization
When testing systems of interconnected components, some of the availability of the components required for testing might be limited at the time of testing. Reasons for this might be:
I. The component itself is not developed yet
II. The component holds insufficient or unusable test data
III. The component is shared with other teams and hence cannot be freely used
In any of the above cases, virtualization of the API can be a valuable solution, enabling testing to continue as planned. API virtualization can be achieved through:
- Stubbing — This is used to create an emulation of an API, mostly used for SOAP and REST web services.
- Virtualization — This enables the simulation of the behavior of complex components, including back-end database connectivity and transport protocols other than HTTP.
- Mocking — This is done for code objects using a framework such as Mockito.
Hence, if you’re planning to test applications in an agile environment, make sure you follow all the best API Test Automation practices mentioned here.
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