Improve test coverage for watch-processor.ts

[samayer12]

Describe what should be investigated or refactored

watch-processor.ts has some gaps in test quality. We should review the test cases in watch-processors.test.ts and improve quality of the unit tests for the watch processor. This was noticed while working on #1757.

Links to any relevant code

Additional context

Here's example output from running npm run test:unit

-----------------------------|---------|----------|---------|---------|-------------------------------------
File                         | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s                   
-----------------------------|---------|----------|---------|---------|-------------------------------------
[...]
  watch-processor.ts         |   75.51 |    61.53 |      60 |   82.02 | 109-110,113,119,125-140,151-152,168