Develop new testing strategy about contracts-ui HOT 3 CLOSED

investigating also camouflage and mock-socket

from contracts-ui.

after going through all the possibilities, looks like the best way is to use simple stubs

this was handled in 59b0024

other strategies are extremely unperformant / hard to maintain

from contracts-ui.

there are some performance considerations to keep in mind:

• running jest in node --experimentalVmModules is slow and leaks memory by itself
• jsdom is slower, but we need it
• running a simple test that renders a component without any @PolkaDot dependencies has aprox 200mb heap in our setup, so that's the starting point
• the code that generates the mock data we use for testing has too many computations, increasing the complexity each time it's called (a lot)
• the app is too tightly coupled with the db (app throws errors if db not connected), not possible to delete db after some tests
• tests mount components, no shallow testing, making everything slow. maybe some snapshot testing could be used here and there
• there might be memory leaks in the app itself, possibly from uncleared subscriptions (subscribeNewHeads)
• another test runner could be tried instead of jest

the memory leaks and heap size were reduced a lot in this PR, but not entirely fixed #90

from contracts-ui.