Which methodology i should use to test func main() in golang?

Question

I have a function main() in main.go that does the job and all other functions are below it (I did not include them here). So, when I write tests for all funcs that are included in main, I can test them. But the code coverage is low because it shows that I did not cover code from my main func.

I know that there is a TestMain func in the testing library that should do the job, but I just cannot get how to get it to work so that the tests cover func main().

Below is my main() func which is not covered by tests...

func main() {
c, err := getConfig()
if err != nil {
    log.Fatal(err)
}
slideshows, err := getSlideshows(c)
if err != nil {
    log.Fatal(err)
}

displaySlideshows(slideshows)

}

Also, I did not find much about it on the internet, so, if this is a stupid question, please, explain to me why this is such a dum problem and where I should search for solutions!

I will appreciate any help!

And if you have real functionality in main(), move it elsewhere to be easier to test, then have main call it. — Flimzy, Jul 11 '18 at 05:59

score 2 · Accepted Answer · answered Jul 11 '18 at 04:31

You can check out "Go coverage with external tests", by Filippo Valsorda:

We create a dummy test that executes main(), we put it behind a build tag, compile a binary with go test -c -cover and then run only that test instead of running the regular binary.

Here's what the rrdns_test.go file looks like:

Note the empty line between the build tag and package:

// +build testrunmain

package main

import "testing"

func TestRunMain(t *testing.T) {
    main()
}
We compile the binary like this:
$ go test -coverpkg="rrdns/..." -c -tags testrunmain rrdns
And then when we want to collect coverage information, we execute this instead of ./rrdns (and run our test battery as usual):
$ ./rrdns.test -test.run "^TestRunMain$" -test.coverprofile=system.out
You must return from main() cleanly for the profile to be written to disk; in RRDNS we do that by catching SIGINT. You can still use command line arguments and standard input normally, just note that you will get two lines of extra output from the test framework.

This is similar to this answer which proposes:

func main() {
    os.Exit(doFunc());
}

Which methodology i should use to test func main() in golang?

1 Answers1