Complete Guide To API Testing | Beginners Need To Know

API testing can be one of the most demanding portions of the software and QA testing because APIs can be complicated. They are frequently established on protocols and standards that we often do not confront in other ways of testing. While creators manage to test only the essential functionality they are working on, testers are in charge of testing performance, functionality, and security of APIs, finding how all elements work together from end to end.

So before going further let’s look at what is API testing. 

Basics of API Testing

API stands for Application Programming Interface. Unlike the user, who interacts with the application barely at the level of UI, the tester must confirm the dependability of any underlying APIs. Without testing the APIs themselves, creators and testers would be clasped manually testing, almost like a user, checking the application at the UI level, waiting until the whole application stack is created before being able to begin testing.

You can rather conduct automated API testing by testing the application at the API level, designing or manufacturing test cases that interact immediately with the underlying APIs, and increasing several advantages, comprising the capacity to test the business logic at a layer that is simple to automate stably. It is not like manual testing, which is restricted to assessing a particular user experience, API testing provides you with the power to bulletproof your application against the foreign.

Also read- Challenges Of API Testing

Testing as a Service

Testing as a Service (TaaS) is an outsourcing criterion in which testing activities related to some of an institution’s firm activities are accomplished by a service provider rather than in-house employees.

TaaS probably comprises engaging consultants to enable and advise employees or solely outsourcing an area of testing to a service provider. Usually, a firm will still do some testing in-house.

It is most suitable for specialized testing endeavours that don’t need a lot of in-depth knowledge of the layout or the system. Services that are well-suited for the TaaS model contain automated regression testing, security testing, performance testing, testing of major ERP (enterprise resource planning) software, application testing, and monitoring/testing of cloud-based applications. Furthermore, TaaS is occasionally known as on-demand testing.

Testing and QA

Software testing and QA (Quality Assurance) are not the exact impressions. They possess distinct objectives, particular features, and methods to apply. Let’s study them. Quality Assurance is a set of strategies and activities designed to assure that the advanced software conforms to all the specifications, for example, BRS, SRS, and FRS. It is a planned technique of the testing process examination directed at the quality product output. QA works out means to avoid possible bugs in the procedure of software development. QA deals further with the management stuff like procedures and methods of development, checklists, project analysis, etc.

QA moves through the entire product life cycle (SDLC) and leads the system of software maintenance. On the other hand, Software Testing is a way of examining the system to assess how it operates and discover possible defects. Several methods are used to test the product, locate bugs, and examine if they are restored. Testing helps consumers the chance to see if the advanced product fulfils their expectations on its design, compatibility, functioning, etc.  Now let’s look at API testing test cases. 

API Testing Test Cases

Let’s look at test cases for API Testing:

1. Verify the keys with the Minimum and Maximum span of APIs for instance, maximum and minimum length
2. Keys verification. If we have JSON, XML APIs we should substantiate that all the keys are appearing
3. Possess a test case to do XML, JSON Schema confirmation
4. Verify the Parse the Response information
5. Valid Response headers and Negative Testcases response
6. Verify how the APIs error codes are handled
7. Verify the answer HTTP status code
8. Valid Response payload
9. Chaining Request verification
10. Verification of APIs with information parameters
11. End to End CRUD flows
12. Database Integrity Test Cases
13. File Upload Testcases

How to do API Testing?

An adequate way to approach API testing is to create a strong testing practice from the bottom up. To this end, a tremendous way to design a test method is to follow Martin Fowler’s testing pyramid. The pyramid approach implies that you construct a wide array of API tests, for example, scenario, contract, performance, etc. on top of a solid organization of unit tests with UI tests. The API tests enable you to check application logic at a level that unit tests cannot. These testing techniques are complementary. Testing before, at the lower levels of the application, enables you to “fail fast and fail early,” catching defects first at their source, instead deceased in the SDLC. Unit testing is crucial, but for now, we are concentrated on API testing.

Below are some tests:

1. Contract Tests
2. Component Tests
3. Scenario Tests
4. Performance Tests
5. Security Tests
6. Omnichannel Tests

Managing Change

Change is one of the most significant indicators of danger to your application. Change can occur in various forms, including:

1. Protocol message format change for a service
2. Components added or removed from an API
3. Basic code change influencing the data format returned
4. Re-architecture of service to break it down into many parts (very prevalent as institutions move to microservices)

As change happens, you desire to have test cases created to identify the change and give remediation plans. Utilizing a solution that furnishes analyses to address the consequence of these changes will enable you to understand what change has occurred and targeted the particular tests that are affected. Change can then be grabbed in the form of a template, to remake any of the elementary components or scenario tests with modern functionality. Since the rest of your tests are related to these tests, the consequence of the change will be decreased.

Constructing a strong automated API testing strategy is the best way to ensure that your applications “work the exact same today as they did yesterday” (it’s more than just a catchy phrase). API testing enables you to create a solid framework for recognizing defects at many layers of your application. These tests can all be automated and run continuously, so you can assure that your application is aligned to business goals while also functionally precise. Since API tests work at a much lower level than UI tests, you know that you will have density and the tests that you are creating will last for a long time to come.

Also read- API Development