API Testing Tutorial for Beginners

An API (Application Programming Interface) is a computer interface that
allows two different software systems to communicate and share data. A
software system that performs an API has numerous functions/subroutines
that may be performed by another software system. Between two software
systems, an API describes the types of requests that can be made, how
they may be made, the data formats that can be utilized, and so on.
Shift Left Testing is one of the most common forms of testing that is now
being asked in API Testing Interviews. Almost every project that follows the
Agile Methodology includes this form of testing.
Prior to the introduction of Shift-Left Testing, software testing occurred only
after the development was completed and the code was provided to the
testers. This strategy resulted in a last-minute scramble to make the
deadline, as well as a significant reduction in product quality.
Besides that, the work required (when errors were discovered at the last
stage before production) was enormous, since developers had to repeat
the design and coding phases.
API Testing is a sort of software test that verifies Application Programming
Interfaces (APIs). The goal of API testing is to ensure that programming
interfaces are functional, reliable, fast, and secure. Instead of utilizing
typical human inputs (keyboard) and outputs, API Testing uses software to
make API calls, get output, and record the system's response. API tests
are distinct from GUI testing in that they do not focus on the appearance
and feel of an application. It focuses mostly on the software architecture's
business logic layer.
API automation is a term that refers to the Testing that necessitates the use
of an API-enabled application. To test an API, you'll need to do a few
things.
To drive the API, use the Testing Tool.
To drive the API, use the Testing Tool.
To test the API, write your own code.
To test the API, write your own code.
You will learn more about- in this API testing lesson.
API Test Environment Setup
API Test Environment Setup
The Different Types of API Output
The Different Types of API Output
API Testing Test Cases are a set of scenarios that are used to test APIs.
API Testing Test Cases are a set of scenarios that are used to test APIs.
API Testing Methodology
API Testing Methodology
There is a distinction between API testing and unit testing.
There is a distinction between API testing and unit testing.
How to Run API Tests
How to Run API Tests
API Testing Best Practices
API Testing Best Practices
Types of Bugs Detected through API Testing
Types of Bugs Detected through API Testing
How to Automate API Testing
How to Automate API Testing
API Testing Challenges
API Testing Challenges
API Testing differs from other methods of software testing in that
there is no GUI, but you must build up an initial environment that
executes API with a specified set of parameters and then checks the
test result.
API Testing differs from other methods of software testing in that
there is no GUI, but you must build up an initial environment that
executes API with a specified set of parameters and then checks the
test result.
As a result, setting up a testing environment for API automation
testing seems to be a little difficult.
As a result, setting up a testing environment for API automation
testing seems to be a little difficult.
The database and server should be set up to meet the application's needs.
The database and server should be set up to meet the application's needs.
After the installation is complete, the API Function should be used to
verify that the API is operational.
After the installation is complete, the API Function should be used to
verify that the API is operational.
An API output might be −
Any kind of information
Any kind of information
current situation (say Pass or Fail)
current situation (say Pass or Fail)
Another API function is called.
Another API function is called.
In this API testing lesson, we'll look at an example of each of the
aforementioned Types.
For instance, there is an API method that adds two integer integers.
Long add(int a, int b)
The figures must be entered as input parameters. The final result should be
the sum of two integer values. This output must be compared to a predicted
result.
It is necessary to make calls, such as
add (1234, 5656)
If the number exceeds the integer limit, an exception must be handled.
Take a look at the API method below −
Lock()
Lock()
Unlock()
Unlock()
Delete()
Delete()
They may return any result as an output, such as True (in the event of
success) or False (in the case of failure).
A more precise Test Case would be to run functions in any of the scripts
and then check for changes in the database or the Application GUI.
In this scenario, one of the API functions is called, which then calls another
function.
For instance, the first API method may be used to delete a specific record
from a table, and this function then calls another function to REFRESH the
database.
API testing test cases are based on
Return value depending on input condition: it's simple to test since
the input can be described and the outcomes can be verified.
Return value depending on input condition: it's simple to test since
the input can be described and the outcomes can be verified.
Does not provide any information: When there is no return value, the
system's API behavior must be examined.
Does not provide any information: When there is no return value, the
system's API behavior must be examined.
Activate another API/event/interrupt: If an API's output causes an
event or interrupt, the events and interrupt listeners should be monitored.
Activate another API/event/interrupt: If an API's output causes an
event or interrupt, the events and interrupt listeners should be monitored.
Update data structure: Updating data structure will have an impact or
consequence on the system, which should be verified.
Update data structure: Updating data structure will have an impact or
consequence on the system, which should be verified.
Modify specific resources: If an API request alters specific resources,
it should be checked by accessing those resources
Modify specific resources: If an API request alters specific resources,
it should be checked by accessing those resources
The API Testing Approach is a predetermined approach or technique that
the QA team will use to conduct API testing after the build is complete. The
source code is not included in this testing. The API testing method aids in a
better understanding of the features, testing approaches, input parameters,
and test case execution.
The following points will assist the user in implementing an API Testing
strategy −
Understanding the API program's functionality and precisely defining
the program's scope
Understanding the API program's functionality and precisely defining
the program's scope
Write test cases for the API using testing approaches such as
equivalence classes, boundary value analysis, and error guessing.
Write test cases for the API using testing approaches such as
equivalence classes, boundary value analysis, and error guessing.
The API's input parameters must be carefully considered and
described.
The API's input parameters must be carefully considered and
described.
Carry out the test scenarios and compare the predicted and actual
outcomes.
Carry out the test scenarios and compare the predicted and actual
outcomes.
The following table highlights the major differences between API Testing
and Unit Testing −
Apart from the standard SDLC process, API automation testing should
include at least the following testing approaches.
Discovery Testing − The test group should manually perform the set of calls defined in the API, such as confirming that a given resource accessible by the API may be listed, created, and destroyed as needed.
Discovery Testing − The test group should manually perform the set of calls defined in the API, such as confirming that a given resource accessible by the API may be listed, created, and destroyed as needed.
Usability Testing − Usability testing ensures that the API is both functional and user-friendly. And how effectively does the API interface with other platforms?
Usability Testing − Usability testing ensures that the API is both functional and user-friendly. And how effectively does the API interface with other platforms?
Security Testing − Testing for security involves determining what form of authentication is necessary and if sensitive data is encrypted through HTTP or both.
Security Testing − Testing for security involves determining what form of authentication is necessary and if sensitive data is encrypted through HTTP or both.
Automated Testing − API testing should result in the establishment of a collection of scripts or a tool that can be used to run the API on a regular basis.
Automated Testing − API testing should result in the establishment of a collection of scripts or a tool that can be used to run the API on a regular basis.
Documentation − The test team must ensure that the documentation is complete and sufficient for interacting with the API. The final output should include documentation.
Documentation − The test team must ensure that the documentation is complete and sufficient for interacting with the API. The final output should include documentation.
API test cases should be organized into categories.
API test cases should be organized into categories.
The declarations of the APIs being called should be included at the
top of each test.
The declarations of the APIs being called should be included at the
top of each test.
The choice of parameters should be stated clearly in the test case.
The choice of parameters should be stated clearly in the test case.
Prioritize API function calls so that testers may easily test them.
Prioritize API function calls so that testers may easily test them.
Each test case should be as self-contained as feasible and free of
dependencies.
Each test case should be as self-contained as feasible and free of
dependencies.
In your development, avoid "test chaining."
In your development, avoid "test chaining."
When using one-time call functions such as Delete, CloseWindow,
and so on, more caution is required.
When using one-time call functions such as Delete, CloseWindow,
and so on, more caution is required.
Call sequencing should be carried out and meticulously planned.
Call sequencing should be carried out and meticulously planned.
Create API test cases for all conceivable input combinations of the
API to guarantee thorough test coverage.
Create API test cases for all conceivable input combinations of the
API to guarantee thorough test coverage.
Fails to gracefully handle error circumstances
Fails to gracefully handle error circumstances
Flags that have never been used
Flags that have never been used
Functionality that is either missing or duplicated
Functionality that is either missing or duplicated
Issues with Reliability Connecting to API and receiving a response is
difficult.
Issues with Reliability Connecting to API and receiving a response is
difficult.
Security Concerns
Security Concerns
Problems with multithreading
Problems with multithreading
Problems with performance. The API response time is really long.
Problems with performance. The API response time is really long.
Errors/warnings to a caller that isn’t correct
Errors/warnings to a caller that isn’t correct
Handling valid argument values incorrectly
Handling valid argument values incorrectly
The data in the response isn't organized properly (JSON or XML)
The data in the response isn't organized properly (JSON or XML)
The lessons that follow give step-by-step guidance to automating API testing.
REST Assured API Testing
REST Assured API Testing
How to use Postman to test an API
How to use Postman to test an API
How can I use UFT to test an API?
How can I use UFT to test an API?
API testing has a number of drawbacks, including −
Parameter Combination, Parameter Selection, and Call Sequencing
are the three main issues in Web API testing.
Parameter Combination, Parameter Selection, and Call Sequencing
are the three main issues in Web API testing.
There is no graphical user interface (GUI) to test the program, making
it impossible to provide input data.
There is no graphical user interface (GUI) to test the program, making
it impossible to provide input data.
It's a bit tough for testers to validate and verify the results on a
separate system.
It's a bit tough for testers to validate and verify the results on a
separate system.
The testers must be aware of parameter selection and classification.
The testers must be aware of parameter selection and classification.
It is necessary to test the exception handling method.
It is necessary to test the exception handling method.
For testers, coding expertise is required.
For testers, coding expertise is required.
The business logic layer is represented by a collection of classes,
functions, and methods in the API. If an API is not well tested, it may create
issues in both the API application and the caller application. In software
engineering, it's a must-do test.