After doing your modifications make sure all tests pass, and add tests to ensure code coverage of your new modifications.
To run the integration tests, you need to have a local fake email server running. The easiest way to do that is with Docker:
$ docker pull ghcr.io/deltachat/mail-server-tester:release
$ docker run -it --rm -p 3025:25 -p 3110:110 -p 3143:143 -p 3465:465 -p 3993:993 ghcr.io/deltachat/mail-server-tester
Leave the fake email server running, open a new shell and run:
$ ./scripts/run_tests.sh
The run_tests.sh script will install deltachat-rpc-server (if needed) and run all tests.
To run all Account tests:
go test -v ./... -run TestAccount
To run a single test, for example TestChat_SetName:
go test -v ./... -run TestChat_SetName