What are different kind of application programming interface testing tools?

There are many testing tools available. Depending on the level of testing required, different tools could be used. Some of the API testing tools available are:

- JVerify: This is from Man Machine Systems. JVerify is a java class/API testing tool that supports a unique invasive testing model. The invasive model allows access to the internals of any Java object from within a test script. The ability to invade class internals facilitates more effective testing at class level, since controllability and observability are enhanced. This can be very valuable when a class has not been designed for testability.

- JavaSpec: JavaSpec is a SunTest's API testing tool. It can be used to test java applications and libraries through their API. JavaSpec guides the users through the entire test creation process and lets them focus on the most critical aspects of testing. Once the user has entered the test data and assertions, JavaSpec automatically generates self-checking tests, HTML, test documentation, and detailed test reports.

To automate API testing, the assumptions are as follows:
- Test engineer is supposed to test some API.
- The APIs are available in form of library(.lib).
- Test engineer has the API document.

There are mainly two things to test in API testing:
Black box testing of the APIs :
In this, we have to test the API for outputs. When we give a known input then we also know the ideal output. So, we have to check for the actual output against the idle output.
A simple program in C can be written as:
- Take the parameters from text file.
- Call the API with these parameters.
- Match the actual and idle output and also check the parameters for good values that are passed with reference.
- Log the result.

Interaction/ integration testing of the APIs.
Suppose there are teo APIs say
Handle h = handle createcontext(void);
When the handle to the device is to be closed then the corresponding function
Bool bishandledeleted = bool deletecontext(handle &h);

Here, we have to call the two APIs and check if they are handled by the created createcontext() and are deleted by the deletecontext().
This will ensure that these two APIs are working fine.For this we can write a simple C program that will do the following:
- Call the two APIs in the same order.
- Pass the output parameter of the first as the input of the second.
- Check for the output parameter of the second API.
- Log the result.