API Testing Basics

Application Programming Interface (API) specifies the way the software components interact by providing a set of functions and procedures to access the data or features of an application or software.

Testing the performance of these functions is an API testing that ensures the long-lasting productivity of the program and flawless operation of all its features.

At the age of agile, API testing had come before the GUI test. Testing code at the highest level was causing an inconvenience for the developers, making them wait for the updated system and ready GUI before the testing could occur.

Now, due to API Contracts, test script can be ready before completing the development so developers may have an opportunity to validate their code based on that test.

API Testing Approach

Developing reliable and durable code requires a thorough and comprehensive API testing covering the full scope of tests. For that purpose, and to make sure that API is operating correctly and fulfills its integrative role, a full understanding of API purpose and functionality is necessary.

API determines all the possible kinds and ways of calls or requests, the data formats, and rules to follow; provides extension mechanisms for users to change the existing functionality in diverse ways and to varying degrees.

API exposes both objects or actions for developer needs and the underlying implementation to simplify programming.

As facilitators for the communication between the user and a server, APIs provide information exchange for two separate systems.

To allow integration with the other systems, APIs are to be scalable, capable of sending many requests with the insignificant code or infrastructural changes, and altogether productive.

API Testing Requirements

API testing requires a full spectrum of checking procedures under different loads of vulnerabilities. API Testing conducts at the message layer and accomplishes verification directly at the API level.

Testers must perform functionality, performance, and security validation of APIs to discover the way all features operate together from end to end.

The API’s tests perform verification of the ability to update a data structure and to trigger some other event or call a different API, checking the return of the values from the APIs under the input conditions.

Testers should specify API output status they need to verify; focus on simple APIs, such as login API and get token API, to enter further APIs and test each API separately.

Organizing all APIs endpoints into categories should be a part of test management, to create testing scenarios.

API testing should perform the following actions
  • Choosing appropriate suite to add the test case;
  • Selecting the test implementation mode;
  • Developing the test cases for the API methods;
  • Configuration of the application control parameters, test conditions, and method validation;
  • API test execution and reports views;
  • Filtering and sequencing of the API test cases;

API Testing Implementation

API testing is implementing at the contract, component, and scenario levels to check API communication specifications, validate each method available in the API separately, and test behavior in different API calls.

Sending a request to API and analyzing the response for correctness is the first step, the so-called happy path. Negative tests follow the happy path to identify all possible incorrect user inputs and secure the best ways of handling errors.

Testers are also responsible for
  • Asserting API reliability for consistent connection;
  • Carrying Load testing to see if the API can handle a large number of calls;
  • Testing API creativity in different ways of usage;
  • Testing API proficiency for increasing tasks; and
  • API documentation testing that also called discovery testing.
Security testing provides validation of access controls, user authorization, encryption of sensitive data, and other security requirements to secure the application and avoid possible vulnerability, potentially destroying the reputation of the product.

Automated testing

Running through API tests requires time, and it can become a problem under the constant pressure of the fast delivery of the product.

Investing in automation test buys the necessary time and means to eliminate repeated tasks, speed up testing, and increase coverage.

The challenges of API Testing

Thorough testing helps developers and QA teams create efficiently working codes. The testers face challenges that are particularly important and can be as followings:

  • API Testing initiation, preparing and running the testing infrastructure;
  • Configuration of the scheme for API Testing with the updating parameters;
  • Formatting the data that handles requests and responses for the API needs throughout the testing process;
  • Testing all possible parameter combinations to examine the problems pertinent to specific configurations;
  • A sequencing challenge that comes with the need for API calls to appear in a particular order to provide a correct performance;
  • Validating the parameters of API requests to ensure that all data passes validation criteria, such as the correct string or numerical type, the length restrictions, and a designated value range;
  • Propagation of the use cases considered the gateway to data for applications communicating through interfaces;
  • The complexity of testing APIs in both separate and nuclear units of performance that increases as testers feature in the calling order of APIs;
  • Versioning of the API to help manage the depreciation of the systems;
  • Providing access to data from multiple APIs and back-end systems;
  • Compliance of the API Testing with the data tracking system.

Overcoming API Testing Challenges

Automated API tests and their integration into a continual delivery cycle is a way to overcome challenges of API testing that includes the following phases:

  • The integration test that focuses on service interfaces and ensures the defined performance of the interface behavior and data sharing;
  • Process testing that embraces business logic, sequencing of the test cases, handling the exceptions, and process dissolution, service, and process reuse included;
  • Implementing the regulatory policies on business, audit, and infrastructure combined with policies on performance, security, and transactions;
  • Ensuring the compliance of the technical solution with the designated criteria for business acceptance.