
FUN – use function module
You can call function modules which get values from various application areas for further processing in the test case using the FUN <function module name> function, (see also
Using function modules).Enter constants, parameters or values or variables in the fields.
Enter variables and parameters which are to be assigned values by the function module.
If the occurrence of an exception during the run should cause termination, enter "X" in the Value field.
Import
You can only specify one record from this table (not a complete table).
Export
You can only export the header record of this table.
You can check for expected exceptions in the function modules with SY-SUBRC.

You will find the function module interface documentation with the function module (transaction SE37).
Maintaining a function in a remote system
You can specify a parameter for remote maintenance after recording with this function, as described under Create a remote call in
REF – Refer to test case.If a parameter with the remote access target is defined, this function is performed remote when the procedure is called. The destination is the current contents of the parameters.