Algernon instances used in tests aren't properly disposed

[gwauge]

User story

As an Algernon dev, I would like to run tests without breaking my working version of Algernon, in order to speed up development time.

Issue

when one runs Algernons test suite (or selected UI tests), these tests apparently open up new Algernon instances to perform their assertions. However it seems they do not properly dispose of the Algernon instance. This results in mutiple Algernon windows being overlayed on top of each other which can only be closed by pressing the close key (i.e. esc) dozens of times or holding it for an extende period of time.
This isn't an issue for CI runs, since the CI image gets deleted. It is however very annoying in the development process.

Reproduction

• run some or all test cases, that include UI assertions
• open Algernon as usual
• observer the background being opaque white, instead of partially transparent
• try closing Algernon

Proposed fix

• global teardown (if possible) that closes all the instance
• shouldn't close the actual instance on the system

Temporary workaround

• run ALGCore allInstances do: [:item | item delete] in your workspace to close all instances
• open up Preferences >> Algernon and re-enable it
• back to normal!