Increase unit-test coverage

[andresmgot]

What happened:

We want at least a 40% coverage for all our plugins (both frontend and backend). At the moment, the coverage for frontend code is 35.25%:

▶ yarn run jest --coverage
--------------------|---------|----------|---------|---------|-------------------------
File                | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s       
--------------------|---------|----------|---------|---------|-------------------------
All files           |   35.25 |    27.44 |   50.67 |   33.72 |                         

Note: the backend coverage is 64.4% so that is fine enough.