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Throughput refers to the NUMBER of transactions PER SECOND that an application can handle under the influence of lot of users (load). The API NEEDS to ensure that required throughput is met before it is deployed on production. We can identify this by performing the Load Testing of the APIs. We can do this by identifying multiple transactions of different priorities and check how many requests are successfully passed in acceptable time governed by the SLAs (Service Level Agreements) defined by us.

Latency refers to the response time or the DELAY taken by the request to reach the SERVER. We need to ENSURE that the latency involved in REACHING the server is minimum as higher the latency, greater is the impact in the application’s speed and PERFORMANCE.

API Specification Review is the first and foremost step of documentation of the API testing needs and REQUIREMENTS. It should clearly STATE the purpose of the API, the APPLICATION workflow and its features along with all other required details which could POSSIBLY HELP to plan the API testing process smoothly.

API testing covers manual and automated testing. Manual testing does not require a tester to know to code. We just need API request details, HEADERS, payload, CREDENTIALS and know how to use the tools required to TEST the system. But in the CASE of automated testing, a tester needs to know how to code to automate test CASES and develop a sophisticated optimised test suite.

Test coverage is a measure that signifies the amount of testing performed by MAKING use of our test cases. It can be either functional testing or non-functional testing of the application. This provides a fair IDEA about what the testers need to COVER in their test cases.

TEST data is the input data used by the testers to EXECUTE their test CASES. This data can be prepared either manually or by MAKING use of tools. For instance, to test the login functionality of an APPLICATION, testers would need input data such as username and password which constitutes the test data.

Black BOX Testing is one of the methods in software testing where the TESTERS evaluate the software functionality without the knowledge of the internal source code. This ideology can be applied in every BRANCH of testing such as UNIT testing, integration testing, system testing and acceptance testing.

• We need to write test cases that correspond with the perspective of end-users.
• Steps defined in the test cases needs to be simple so that anyone can replicate the steps.
• Ensure that the test cases are reusable.
• Define and set the priority of test cases.
• Provide a valid description, test input parameters, test DATA, EXPECTED outcome after running the test cases so that we can COMPARE the ACTUAL outcomes of the test cases with the expected ones.
• Make sure to develop test cases that cover negative test scenarios too.
• Naming conventions need to be properly FOLLOWED while developing test cases.
• Review them regularly and update them as and when the functionality gets updated.

In API Testing, we send a request to the API and then we analyze the responses BASED on the FOLLOWING parameters:

1. Data accuracy of the actual response with the expected response.
2. HTTP status codes of the resultant API.
3. Response time of the API.
4. Error codes if the APIS are expected to throw an error.
5. Authorization Details
6. Test non-functional specifications of the applications like security, performance, availability ETC.

We follow the below approaches in API Testing:

• Firstly, write required TEST cases for testing the APIs by making use of different testing techniques like EQUIVALENCE class, boundary value analysis etc that HELPS to verify the functionalities.
• Clearly define the scope and functionality of the APIs.
• Define the different input parameters that you want to test the API with.
• Verify the test cases by passing the input parameters.
• Compare the results of the different test cases based on their expected behavior.
• Also subject the API to different CONDITIONS depending on the description of the functionality.

There are various advantages of API testing. Some of the most significant advantages are as FOLLOWS:

• Core Functionality Testing: This kind of testing provides access to the entire system without the need for a user interface. The functionalities of the application would be evaluated end-to-end without the need for GUI (Graphical User Interface) which helps in detecting issues that can prove to be bigger at the time of GUI testing.
• Time and COST EFFECTIVENESS: This is usually less time-consuming when compared to GUI testing. It also requires less code for testing the functionalities thereby making it easier to SET up and get faster access to test coverage. It also RESULTS in effective cost savings for the project.
• Language-Independent: The data transfer between the test platform to the applications is done utilizing XML or JSON and is completely independent of the languages used in developing the systems. The test automation suite can be developed in any language.
• Ease of Integration with GUI: API testing provides highly flexible test suites that help in easier integration with the GUI tests. For instance, before the GUI test cases are initiated, employing API test cases, we can create sample users that can act as an initial base for the GUI tests.

The most popularly used TOOL in the market is PostMan. This tool helps to CREATE MANUAL and automated test cases for testing the APIs in a well-designed manner. APART from this, there are different tools like JMeter, Parasoft SOAtest, SoapUI, Apigee, API fortress, JUnit, etc.

API TESTING can be USED for testing the FOLLOWING PROTOCOLS:

• HTTP
• REST
• SOAP
• JMS
• UDDI

There are VARIOUS types of API testing, they are:

• FUNCTIONAL Testing
• Unit Testing
• Load Testing
• Security Testing
• UI Testing
• Interoperability and WS compliance Testing
• Penetration Testing (PEN Test)
• Fuzz Testing.

The general workflow of API is that it takes a REQUEST, processes it which MIGHT involve data validation, database interaction, data processing, and then the resultant of this is sent back to the SOURCE. APIs provide an abstraction to the internal business logic as they are not exposed to the world.

Examples of APIs: Amazon API, Google Map API, TWITTER API, ETC.

API stands for Application Programming Interface that is useful for communication between different software systems. It facilitates data EXCHANGE between systems LOCATED in different REMOTE places. They are nothing but a collection of functions that are executable by other functions of the software application.

API testing is a CATEGORY of software integration testing that deals with the testing of APPLICATION Programming INTERFACES (APIs) directly. It deals with checking if the APIs developed work as expected in terms of reliability, FUNCTIONALITY, security, and performance of the business logic covered by the applications.