Unit test execution speed (how many tests per second?)

Question

What kind of execution rate do you aim for with your unit tests (# test per second)? How long is too long for an individual unit test?

I\'d be interested in knowing if

Answer 1

How long is too long for an individual unit test?

I'd say it depends on the compile speed. One usually executes the tests at every compile. The objective of unit testing is not to slow down, but to bring a message "nothing broken, go on" (or "something broke, STOP").

I do not bother about test execution speed until this is something that starts to get annoying.

The danger is to stop running the tests because they're too slow.

Finally, when you do decide the tests need to run faster, what techniques do you use to speed up your tests?

First thing to do is to manage to find out why they are too slow, and wether the issue is in the unit tests or in the code under test ?

I'd try to break the test suite into several logical parts, running only the part that is supposedly affected by the code I changed at every compile. I'd run the other suites less often, perhaps once a day, or when in doubt I could have broken something, and at least before integrating.