On requiring test cases for all bug fixes

[orangemocha]

All Pull Requests that either fix bugs or introduce new functionality require at least one test case demonstrating the defect or validating the intended functionality. For bug fixes, the test should fail before the change, and pass after the change.

In some cases, this might be a difficult task / the test case might be too large to fit into a unit test. We should leave some flexibility in this policy and clarify when a bug fix can be taken without a test case.

[srl295]

@orangemocha glad I hit reload before filing a dup. 👍
Perhaps something such as:

In exceptional cases, such as environments or failure modes difficult to reproduce, a detailed testing
description may be accepted in lieu of a specific test.

[Fishrock123]

Here's an example, for posterity: nodejs/node@c9207f7

[orangemocha]

Memory leaks are another good example.