API Tester: Why It Matters, And API Testing Tools To Use


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Before you get to know the API Tester, let’s start to know what is the API and how it works. Further, we will discuss API integration and open API. API stands for Application Programming Interface. API acts as a connection intermediary between a program or our website and other programs that are out of the system. It depends on the user’s needs. For example, the Google Maps API is another Google service that enables us to use Google Maps’ information on our website.

Steps to use API Testing Tools

The following steps demonstrate how we use API Tester:

Unit Testing

To test the source code by the script to determine whether the developed code is working properly, we write a Unit test to check the code in the section called Stored Procedure. This is done to determine for sure whether the query is correct.

Functional Testing

The functional test is the test of the API service that sends and receives responses to determine whether it is the correct information. For example, login service must receive two parameters: Username and Password, primarily from the request, and the system must return a user token to continue using it. For example, if the user fills more than that, you can set that Alerts must return to the API Service.

Load Testing

It is a test to determine how much concurrent can support and how slow the response time is.

Security Testing

The tests in this section are to see how to secure the service we use. We also focus on entering the value of each parameter with some commands that may affect the back end system, such as entering SQL statements or SQL injection by attaching commands to the required input parameter, such as entering the drop database command to password parameter in login service and request service.

What is the role of API Tester?

Nowadays, most technologies often use ANIS to connect to systems such as online sales systems, often with AN API connected to your bank so that users can pay online. Therefore, API testing is of great importance, because sometimes performing UI-specific tests or testing through web pages may not be determined whether the test function is performed.

What value does API bring?

API is being used in various systems these days. Most of these systems are responsible for connecting websites to database systems, whether it’s bringing data from a database on a website or entering (Insert) new information into the database system. We can say for sure that if API testing is done properly, it will make the usage of the system more error-free and efficient, helping us to do our work faster and better.

The benefits of the test are as following:

  1. To provide the system in the Get-send section
  2. Reduce the test time in database testing, such as querying data to determine if the data is recorded correctly
  3. It can help Programmers or developers find root causes of bugs
  4. To make the system more secure

How useful API testing is, depends on how important the API is in the system? If it is a system that uses a large number of Third Party through API Service, you can use third party services. The API test will see more results.

API testing tools

We can divide API testing into two forms: Manual Testing and Automation Testing:


Postman is an API test tool suitable for manual testing and is very popular because of its value. Users can enter values through the screen and press Request to see the results of the API Service. However, there are some limitations, most of which are listed below:

Advantages of Postman:

There exists a free version.

  1. We can record collections in the test.
  2. We can forward values between API Service to reuse.
  3. We can write Groovy Script to Mock Up data for testing.
  4. Postman Restrictions
  5. The value cannot be checked to the Database level.
  6. The Load test API cannot be performed.


SoapUI is an automation API testing tool where users can design API tests based on user needs.

Advantages of SoapUI:

  1. There is a version that is an open-source free of charge.
  2. It can be tested from the API level to compare to Database.
  3. Test Suite and Test Case can be divided and send values to other services under Test Suite or Test Case.
  4. We can use Groovy Script to Mock Up Data and issue a report.
  5. Other features are available in addition to functional testing, Load Test, and Security Test.

Disadvantages of SoapUI:

  1. The program is relatively slow, potentially causing crashes sometimes.
  2. User Interface looks quite difficult to use.
  3. One API test will require multiple set-ups (e.g. create rest service /Create Test Suite/ Test case/Test step).

Finally, the API Test ensures that the data sent from the front-end to back-end through the API service will work more accurately. It also improves the efficiency of the back-end data display from before QA tests the display through the website and compares the data in the database to match. If we have an intermediary API test between these two. It will help to determine whether data we receive and send is more accurate. If you have any further questions about the process, tools, or value of the API tester, please feel free to address them below in the comments section.

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