Add ability to specify number of tests to the quickcheck macro

[Wilfred]

I have a quickcheck test using Vec<EnumWithManyVariants> and my tests rarely fail. It would be nice if I could set an environment variable to make quickcheck try more possible inputs.

[BurntSushi]

@Wilfred To clarify, have you seen the tests method? http://burntsushi.net/rustdoc/quickcheck/struct.QuickCheck.html#method.tests Or are you specifically asking for this to be settable via an environment variable?

[astahfrom]

It would be nice to be able to control this when using the #[quickcheck] attribute also.

[Wilfred]

I think my use case is probably the same as Andreas: I have a load of tests using the #[quickcheck] attribute and I can't change the number of tests run. It would probably make more sense if it could be controlled per-test, so I could increase the number for tests which I've observed to find failures occasionally.

[remexre]

I think this is already implemented: https://github.com/remexre/quickcheck/blame/master/src/tester.rs#L20

Close as fixed?

[Wilfred]

That's certainly helpful, because users can explicitly re-run a single test and set QUICKCHECK_TESTS to explore more test cases if they wish.

However, it doesn't meet the following usecases:

• If I have a test that runs slowly, I might want to lower the number of test cases attempted
• If I have a fast test and a large test case space (so my tests occasionally fail when doing TDD), I might want to increase the number of test cases attempted

In both of these cases, I want to change the number of test cases per test, and make a permanent change.

That's my usecase at least. If you think the current functionality is sufficient for quickcheck's goals, I understand.

[remexre]

It'd be "probably not too hard" to change the quickcheck! macro to allow a per-test #[quickcheck_tests = 1234] attribute as well; if you want to try that, feel free, otherwise I might play around with it if I have a free weekend.