Are u talking about the testing, think so...ok

 After the integration of your module with the other 
modules you can still test.

For that we have a testing technique called "Regression 
Testing" which is mainly for the testing of integrated 
modules. It helps to check whether your module works 
properly as required with other without any problem/defect. 

And in that case you can test using the same testcases, 
which you have used earlier for that module.

When the modules are integrated, then the whole application 
is tested through integration testing.

Regression testing is basically testing the changed code 
against the existing code on the same test data(which was 
used for previous testing) and then executing the processes 
to validate the data.