Excluding Generated Mocks From Coverage

By Jon Colby

Some projects make rather heavy use of gomock for testing, and I’ve noticed the command that I had been using to run all tests and generate coverage included the mocks in coverage and brought the numbers down.

We can’t allow numbers to go down! Here’s an altered Makefile snippet to generate test coverage.

Command

test:
    $(eval COV_PKGS=$(shell go list ./... | grep -v mock_ | tr '\n' ','))
    go test ./... -race -cover -covermode=atomic -coverprofile=build/cover.out -coverpkg $(COV_PKGS) 
    go tool cover -func build/cover.out | grep total

Explanation

All of the mocks for this project are under sub packages with the pattern mock_${PKG_HERE}. Some important interface in package thingy will have a mock in the package path/to/thingy_pkg/mock_thingy_pkg/thingy.go.

Explanation of the commands:

  1. eval a variable COV_PKGS

    • execute go list ./...
    • Filter all packages that contain mock_ with grep -v
    • Replace the newline in the output with a ,

  2. Tell go to only calculate coverage on the packages in ${COV_PKGS}