Failing fast to learn a lot

One of my collegues had an intereseting error report from our test suit today:

Error: “Expected 3 but was 3”

At first glance it might seem that everything is as expected!! actually it’s not but finding where the error is might be a little tricky. There’s not a lot of information to start with.

The problem is a some what shaky implementation of the unit test framework we’re using. The line of code that reports the error looks like
ASSERT_EQ(++errorCount, errorHandler.Errors.Count);

I personally don’t like the ++errorCount argument but would expect it to be fine except ASSERT_EQ is a macro and the argument is used once for comparison and once for outputting and hence incremented twice

Moral: If you’re not 100% sure what a macro does and you need it to work on a value pass a value. Only pass expressions when the macro needs an expression and not a value.