The BootstrapTrait and Unit Tests
I added a test that installs Vanilla with the SiteTestTrait and found that a bunch of our other tests broke. After some digging I found that they were relying on a fresh bootstrap and container. To fix this I create a BootstrapTrait for tests to use if they want to test with the container.
If you write a test that uses the container (which includes anything that calls t()) then you will need to use this trait. The SiteTestTrait already uses the bootstrap so you don't need it there.
The relevant changes are in this commit. You can scroll down to see how the test classes use it.
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