test_server and timetraps

Jayson Vantuyl <>
Mon Dec 7 09:53:41 CET 2009

Just to save anybody else the trouble, test_server has some... interesting behavior.

I had tests with timeouts of 5 seconds that would run for 15 and still not be killed.  This seemed odd, so I checked it out.

Apparently, when certain options are turned on, the test_server will scale up your timeouts.  Buried deep within the bowels of test_server, there is a sprinkling of code that determines a "multiplier" for your timetraps.  Apparently, it considers running under code coverage reason to scale your timeout by a factor of 10!  This was definitely a surprise.  Although, I admit that the fact that running on VXworks increases timeouts by another factor 5 was good for a laugh.

I decided to mail the list so that this would be on the webs for people to find.

It turns out that it is documented in test_server, but not in common_test.  Can somebody document this in common_test, so that people don't wonder why their timetraps seemingly never kick in?  The built in testing / debugging / tracing under Erlang is absolutely wonderful, but it's so woefully documented that I'm surprised that anybody uses it.  Let's just say a 12 minute timeout becoming a two hour timeout is not "expected behavior".  :(

Jayson Vantuyl

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