this is a good article that define how to do network calls from front . IF you check each implementation it mention browser support
I might be late to answer.
If you are looking specifically for coverage while using Cypress for E2E, you can check this doc: https://docs.cypress.io/guides/tooling/code-coverage.html#Introduction
Here it is shown that we can measure code coverage using additional plugins though this coverage is just an indicator of what all lines of code are not at all ...