External behavior and integration testing
As seen, the creation of unit tests and benchmark tests within Go is very simple and intuitive. The built in go test command allows various coverage capabilities. A little known capability of the go test tool is the ability to specify which packages you wish to generate coverage information about with the -coverpkg flag. Armed with this information, we can formulate a go test command that will be able to run against the main package in our program but collect coverage information about our handlers package:
go test -coverprofile=cov.txt -coverpkg ./handlers -run TestRunMain ./cmd/service/
The preceding command is saying run tests against the main package but collect the coverage information from handlers that in turn will use the cover tool to instrument the handlers code to keep track of coverage numbers in the handlers package. If we take this concept to the next logical step, what happens if we have one test in cmd/service/main_test.go that merely...
