Update TESTNAME instructions in CONTRIBUTING.md

[rthomas]

When trying to run a specific test, I found the contributing docs a bit confusing and through a bit of googling found out that TESTNAME takes the fully qual'd name of the test.

I'm unsure if this can also take the source file, but I was unable to get that to work.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[alexcrichton]

Actually I think that TESTNAME is basically just a string match against the name of each test. For example all of the run-pass tests are named after the basename of their files, and the libstd tests are named based on modules and such. So for example the test you mentioned below would also be matched with the filters collections, capacity, hash::map, etc.

[rthomas]

Right, thanks Alex - I've been trying to find how this is matched with not much luck. The reason I wanted to make it a little clearer was when I tried with the file path as suggested I couldn't get it to work - e.g. I used TESTNAME=src/libstd/collections/hash/map.rs to try to run the tests there.

I'd like to try to find how this is implemented, so I can update the docs if it is just pattern matching as you say.

[hanna-kruppe]

It's most likely implemented in src/libtest/lib.rs.

[alexcrichton]

Yes this is specifically implemented here

[nagisa]

This uses substring match. You can use TESTNAME=abc to run all the tests with abc in the name.

[rthomas]

Thanks all, I've updated the docs again to specify substring matching.

[alexcrichton]

@bors: r+ df31868 rollup

Thanks!

[dirk]

Should these documentation improvements also be made in make tips? Right now it doesn't really provide the helpful details that are present in CONTRIBUTING.md.

Here are the relevant testing bits currently outputted by make tips:

  * check-$(crate) - Test a crate, e.g. `check-std`
  * check-ref - Run the language reference tests
  * check-docs - Test the documentation examples
  * check-stage$(stage)-$(crate) - Test a crate in a specific stage
  * check-stage$(stage)-{rpass,rfail,cfail,rmake,...} - Run tests in src/test/
  * check-stage1-T-$(target)-H-$(host) - Run cross-compiled-tests

  ...

  // Modifying libstd? Use this command to run unit tests just on your change
  make check-stage1-std NO_REBUILD=1 NO_BENCH=1

  // Added a run-pass test? Use this to test running your test
  make check-stage1-rpass TESTNAME=my-shiny-new-test

  // Having trouble figuring out which test is failing? Turn off parallel tests
  make check-stage1-std RUST_TEST_THREADS=1

I'd be happy to make these updates/edits if you all think they're worth making. 😄