What are different testing mechanisms used to test the sofware?

After deciding the inputs and outputs for the test cases, another issue that comes into picture is writing the code that actually tests the software. Following mechanisms can be used to write codes:

- TEST DRIVERS
The lower level modules can be tested by using a test driver program. Approach that is used is to write a program that passes input data to the unit under test and comparing the output to truth. Input is selected from uniform testing, Monte Carlo testing, selected input conditions or from manufactured data. Output is compared against trusted results using an inverse function or a file containing correct data.

- WHITE BOX TESTING
Test drivers can also be used to test several modules at once to save time if you are doing white box testing. White box testing taken advantage of the internal working of the module under test. This approach saves time but disadvantages include while testing several things together, you may get a right answer indicating that everything is right but if you do not get the right answer then you are not sure what went wrong.

- BLACK BOX TESTING
This testing does not depend on the internal working of the module unde test. It only depends on the inputs and outputs of the system.

- TEST STUBS
Test Drivers are high level routines that call lower level subprograms, test stubs can be used to test higher levels of program. Stub is a simple routine that takes the place of real routine. It may be a null procedure or it may have a simple message. There is no need for test stubs to be limited to fixed data or user supplied data. Stubs need not be just input stimulators. Stubs also display or record data sent to them.

- TEST AND DEMO PROGRAMS
A test program usually does not involve much operator intervention. A demo program is a quick confidence check.