ways o testing API's code example

Example 1: have you done api testing

I have worked on API testing in my project and I used
POSTMAN for manually testing and REST ASSURED
java LIBRARY for automation.
I used JDBC and it is a Java-based data access technology
used for Java database connectivity. It provides classes and
interfaces to connect or communicate Java application with
database.
JDBC API is a Java API that can access any kind of data
stored in a Relational Database. It enables Java programs to
execute SQL statements.

Example 2: api testing approach

Write suitable test cases for the APIs and use testing techniques 
like exploratory testing, boundary value analysis, positive and negative 
testing for understanding the functionality.

 Verify the calls with combination of two or more value added parameters.
 Define the scope and basic functionality of the API program.
 Define the accurate input parameters.
 Test case execution and comparison of the results with expected results.
 Determining API behavior under conditions like the connection with files,
etc.

- There are different types of output observed of an API also:

The main consideration is returning correct results under any type of 
conditions. Mainly, the output or results observed of an API are divided 
into three sections as follows:Returning the result status values as ‘Pass’ or ‘Fail’.
 Result as data or any specific information.
 An event where the call to any API function will initiate the call to 
another API function