`R3TestBed` allows consumers to configure a "testing module", declare components, override various metadata, etc. To do this, it implements its own JIT compilation, where components/directives/modules have Ivy definition fields generated based on testing metadata. It results in tests interfering with each other. One test might override something in a component that another test tries to use normally, causing failures.
In order to resolve this problem, we store current components/directives/modules defs before applying overrides and re-compiling. Once the test is complete, we restore initial defs, so the next tests interact with "clean" components.
PR Close#27786
Andrew Kushnir
Kara Erickson
Pawel Kozlowski
Miško Hevery
Victor Berchet