improve mocking framework for tests

[panentheos]

Summary of changes

This makes several improvements related to mocking and test infrastructure.

• Stores mockable module references in the application environment rather than process state. This reduces the amount of per-process state, and simplifies several code paths.
• Inlines callback specs in the relevant engine modules, rather than maintaining separate behavior modules.
• Defines proper mocks for bus-related engines.
• Enables the capture_log option, eliminating log spam when running tests (logs will still be printed if a test fails).

[digitalcora]

I like it! 🧹

[digitalcora]

What do these removals relate to? Not sure how they tie into the mocking changes.

[panentheos]

Oh, this leaked through from another change I was testing, but backed out. I was seeing if we could disable the application entirely in test mode to further reduce log spam. There were a handful of tests that failed because they access the actual application processes.

Even though it's unrelated, this still seems worth keeping, because this style of test is unnecessarily brittle for what it's doing. The two deleted cases were duplicated by other tests later in the file, and the third one is rewritten to use the more isolated approach.

[digitalcora]

Gotcha. I'd agree this seems brittle, and if the behavior is already covered by other tests, no problem with removing these.

[digitalcora]

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