Object Oriented ABAP

Introduction:
Understanding "ABAP Unit"
It is a best practice to modularize our programs as much as we can for better
programming. If we want to check one particular module like subroutines, function modules
or classes for bugs then we can do it using ABAP Unit. ABAP Unit is a tool for unit testing of
ABAP programs.
How to write these tests:
ABAP unit is based on ABAP objects. The global class CL_AUNIT_ASSERT contains methods
which can be used for testing .Tests are implemented in local classes. Inside the local class
the necessary method from the global class can be called for testing. These test classes can
be written inside the program for which the test is to be done. It will not affect our
production code in anyways.
Difference between Ordinary class and Test class:
Both the test class and test method should have FOR TESTING addition.
Ex:
CLASS mytest DEFINITION FOR TESTING.
PRIVATE SECTION.
METHODS mytest FOR TESTING.
ENDCLASS.
Methods in CL_AUNIT_ASSERT for Testing:
ASSERT_EQUALS
ASSERT_DIFFERS
ASSERT_BOUND
ASSERT_NOT_BOUND
ASSERT_INITIAL
ASSERT_NOT_INITIAL
ASSERT_CHAR_CP
ASSERT_CHAR_NP
ASSERT_EQUALS_F
FAIL
ABORT
ASSERT_EQUALS - Checks the equality of two data objects.
ASSERT_DIFFERS - Checks for the difference of two data objects.