The point of Test suite is that it proves that it will work. If the test is not working a with a particular value( for example). Then you write a test to prove your point and then they will have to fix it. Once you have a test, you will always keep the test because that will be validation that any code changes that they implement will work.

They way you are doing things, without a test suite, you only have two things which say your code works. Your co-worker says that it works and that your program does not crash. How do you know that it works correctly? Suppose your program puts a NULL value into database instead of ''? Your program may not crash but that does not mean it is doing the right thing.

Think of it another way, if CPAN did not have any tests, do you think that Perl would be anywhere near where it is today? There would be no way of verifying if there was a bug with a particular version of Perl, or Linux, or a module. Your program would keep crashing and you would have no easy way to determine where you have a bug.