Web API testing may be defined as the testing performed on web services for functionality, performance, security, and reliability. Several types of testing can be conducted on a Web API. Some of them are listed below:
- Functional Testing:
| Purpose | Scenarios | Example |
| To validate that the API acts/responds in a manner as expected test. | The testing of whether API endpoints return results as expected for valid requests. | Testing if a new resource is created due to a POST request or does a GET request return the value of the appropriate data. |
- Integration Testing:
| Purpose | Scenarios | Example |
| Verifies that various parts of the API, such as services and/or databases, integrate correctly. | The usage of verification of proper integration between API endpoints with various databases, other services, or components involved is included.Negative scenarios like negative inputs, missed inputs, and data not found are also included. | This would include how a POST request correctly inserts data into a database. |
- Performance Testing:
| Purpose | Scenarios | Example |
| Assesses the speed, responsiveness, and stability of the API across a variety of conditions. | 1. Load Testing: Tests how the API acts under conditions of normal load. It simulates high traffic to realize how the API reacts under it. 2. Stress Testing: This is to find out the reaction of API under extreme or peak load conditions. 3. Spike Testing: Tests how API reacts when there is a sudden rise in traffic. 4. Endurance Testing: This testing will determine how the API sustains in long periods of use. | The performance of API for a longer period of time in case of high load of requests. |
Security Testing:
| Purpose | Scenarios | Example |
| Ensures that API is secure against vulnerabilities and attacks. | Pinpoint common security issues like flaws in authentication, data leakage, or injection attacks. | Testing authentication handling, such as OAuth; encryption, such as SSL/TLS; and access control within the API |
- Backward Compatibility Testing:
| Purpose | Scenarios | Example |
| This assurance allows your API to operate over varying devices and on several different browsers. | Identifies that API works on several operating systems, browsers, or devices. | The API works seamlessly on both HTTP/HTTPS protocols and different client environments, such as mobile and desktop. |
- Benchmarking Testing:
| Purpose | Scenarios | Example |
| To ensure the API functions well with edge cases/boundary conditions. | Test inputs that are at the edge of valid input ranges. | Sending a maximum or minimum value for an integer parameter. |
- Chaos/Resilience Testing:
| Purpose | Scenarios | Example |
| Ensures that the API is still available in case of the unavailability of components such as database, hardware, etc. | Testing the API for some time while some of the dependencies are unavailable and capturing the responses. | Bring down the database connectivity during the tests for some time and bring it back up. API must be able to sustain the system unavailability. |
By performing all or a combination of these tests, the developers make sure that a Web API is reliable, secure, and functional in various scenarios and environments.