Excluding files from code coverage in GO

Talal Yousif — Tue, 17 May 2022 09:47:11 +0000

It's not uncommon to find yourself in a situation where you would like to make an exception for some code from being included in code coverage; perhaps it's auto-generated code or perhaps it's a wrapper of a third party API. Unfortunately, unlike many other languages, there is no built-in way to do this in Go (Hopefully not for too long). In this article, we go over a simple workaround to achieve this goal.

First things first, a quick recap. Code coverage can be generated using the go cover tool. From the docs, usage of the tool is described as:

Usage of 'go tool cover':
Given a coverage profile produced by 'go test':
go test -coverprofile=c.out
Open a web browser displaying annotated source code:
go tool cover -html=c.out

As such, we first run our tests using:



go test ./... -coverprofile=coverage.out

Subsequently, we generate code coverage using:



go tool cover -html=coverage.out

I like to run the commands one after the other in one call, like so:



go test ./... -coverprofile=coverage.out && go tool cover -html=coverage.out

The workaround

It's simple. Code coverage is generated based on the coverprofile which is no more than a plain text file annotating which lines of each code file are covered and which are not. Remove all lines about a file from the coverprofile and it won't be included in the code coverage report. As simple as that.

Here is what a coverprofile looks like

It wouldn't be ideal if we have to manually manipulate the coverprofile every time we want to generate code coverage. A better way would be to automate this process. For that, We need to do 2 things. The first is a file that holds paths to files to be excluded from code coverage. File paths in this file should include the full package name. I created a file named "exclude-from-code-coverage.txt". Here is a snippet of what it looks like

The second is a script that removes files in exclude-from-code-coverage.txt from the coverprofile. This simple script (named exclude-from-code-coverage.sh) does just that:



#!/bin/sh
while read p || [ -n "$p" ] 
do  
sed -i '' "/${p//\//\\/}/d" ./coverage.out 
done < ./exclude-from-code-coverage.txt

And finally, tying it all together:



go test ./... -coverprofile=coverage.out && ./exclude-from-code-coverage.sh && go tool cover -html=coverage.out

Let's break it down:

The first command, go test ./... -coverprofile=coverage.out runs the tests and generates the coverprofile.
The second command, ./exclude-from-code-coverage.sh, removes files we want to exclude from code coverage from the coverprofile.
The third command, go tool cover -html=coverage.out, generated the code coverage report.

DEV Community: Talal Yousif

Excluding files from code coverage in GO

The workaround