Put double plan checks into an event watcher

[schwernbot]

From: @schwern Date: Monday Nov 07, 2011 at 22:30 GMT Orig: https://github.com/Test-More/test-more/issues/184

Test::Builder has its own checks for a double plan, both in done_testing and elsewhere. It cannot do this alone, other builders might issue plans without its knowledge. This includes subtests.

• Write an event watcher whose job is it to ensure there is only one plan.
• Test::Builder will add it to the TestState by default.
• Retain Test::Builder's nice error messages.

This will probably require adding more information to the SetPlan event, like "who did it" in order to identify what method the user called to set the plan (if it was done_testing) or whatever.

[schwernbot]

From: @schwern Date: Friday Nov 11, 2011 at 02:48 GMT Orig: https://github.com/Test-More/test-more/issues/184#issuecomment-2704305

This went through some pain to retain the ability to specify both a plan and use done_testing. I'm tempted to drop that, at least the redundant plan tests => 5 and done_testing(5).