Calypsoify: Add test to fail under 9.2

[kraftbj]

See #17939

Adds an unit test to call the mock_masterbar_activation function to ensure it doesn't error.

As it stands, this PR will fail. Coupled with 17939, it should pass.

Changes proposed in this Pull Request:

• Adds unit test.

Jetpack product discussion

n/a

Does this pull request change what data or activity we track or use?

No

Testing instructions:

• Unit tests should fail. You can test directly under yarn docker:phpunit --testsuite=calyposify
• Merged into 17939 or into master after that's merged, it should pass.

Proposed changelog entry for your changes:

• n/a

[kraftbj]

This branch by itself:

This branch merged into 17939:

[kraftbj]

I'll follow up with some minor production code changes to make this easier to test with confidence. This test would probably still pass in a situation where there masterbar is loaded elsewhere in the test run since it only makes sure the class exists.

The production code probably can be tweaked to return an instance of the masterbar class, but I didn't want to touch production code for the sake of the test as part of something intended for a point release.

[jetpackbot]

	Warnings
⚠️	The PR is missing at least one [Status] label. Suggestions: [Status] In Progress, [Status] Needs Review

This is an automated check which relies on PULL_REQUEST_TEMPLATE. We encourage you to follow that template as it helps Jetpack maintainers do their job. If you think 'Testing instructions' or 'Proposed changelog entry' are not needed for your PR - please explain why you think so. Thanks for cooperation 🤖

Generated by 🚫 dangerJS against b4412c2