<h1> How to Debug custom functions in QTP ? </h1>

Verify the code works when it is not within a function. If the code does not work when it is not in a function in a QuickTest Professional (QTP) script or within a pure VBS script (while QuickTest Professional is not in use), it will not work when it is placed within a function. The following example shows the step by step process of debugging a simple function.
Example:

Function ex_func(obj, txt)
msgbxo obj.Exist
msgboxx txt
End Function

To debug the above function (which has intentional typos), copy the statements into a QuickTest Professional script:

msgbxo obj.Exist
msgboxx txt

If needed, modify any references to a generic object to an actual object:

msgbxo Browser("Browser").Exist
msgboxx txt

Execute the code; debug as needed:

msgbox Browser("Browser").Exist ' corrected typo: msgbxo -> msgbox
msgbox txt ' corrected typo: msgboxx –> msgbox

Copy the corrected code into the function. Verify it works as expected:

Function ex_func(obj, txt)
msgbox Browser("Browser").Exist
msgbox txt
End Function

If needed, modify references to specific objects back to general references:

Function ex_func(obj, txt)
msgbox obj.Exist
msgbox txt
End Function

Verify the function works as expected.
(Optional) Move the function into a function library.

If function is returning a value, the value should be assigned to the function name. This is a VBScript requirement.
Example:
Function examplefunc
examplefunc = "returned value"
End Function
msgbox examplefunc

If function is saved in an external function library, make sure it associate the function library with the test script.