The pytest-xdist plugin extends py.test with some unique test execution modes:
* test run parallelization: if you have multiple CPUs or hosts you can use
  those for a combined test run. This allows to speed up development or to use
  special resources of remote machines.
* --boxed: (not available on Windows) run each test in a boxed subprocess to
  survive SEGFAULTS or otherwise dying processes
* --looponfail: run your tests repeatedly in a subprocess. After each run
  py.test waits until a file in your project changes and then re-runs the
  previously failing tests. This is repeated until all tests pass after which
  again a full run is performed.
* Multi-Platform coverage: you can specify different Python interpreters or
  different platforms and run tests in parallel on all of them.

(adam)