go test coverage rate not work for exec.Command

[suchen-sci]

To test os.Exit(), one way is to use exec.Command and check exit status. But in this case, since exec.Command open a new process to call exit func, the coverage rate for main test is still zero.

For example, example by Andrew Gerrand

package main

import (
    "fmt"
    "os"
)

func Crasher() {
    fmt.Println("Going down in flames!")
    os.Exit(1)
}

package main

import (
    "os"
    "os/exec"
    "testing"
)

func TestCrasher(t *testing.T) {
    if os.Getenv("BE_CRASHER") == "1" {
        Crasher()
        return
    }
    cmd := exec.Command(os.Args[0], "-test.run=TestCrasher")
    cmd.Env = append(os.Environ(), "BE_CRASHER=1")
    err := cmd.Run()
    if e, ok := err.(*exec.ExitError); ok && !e.Success() {
        return
    }
    t.Fatalf("process ran with err %v, want exit status 1", err)
}

In this case, the coverage rate for Exit is still zero although we have a test for it.

I think this is a problem for all similar cases, if test start new processes to test the function

[seankhliao]

Related #30219
Duplicate of #31007