With a slight refactoring, you may easily achieve 100% coverage.
foo/bar.go
:
package foo
import (
"fmt"
"os"
)
var osExit = os.Exit
func Crasher() {
fmt.Println("Going down in flames!")
osExit(1)
}
And the testing code: foo/bar_test.go
:
package foo
import "testing"
func TestCrasher(t *testing.T) {
// Save current function and restore at the end:
oldOsExit := osExit
defer func() { osExit = oldOsExit }()
var got int
myExit := func(code int) {
got = code
}
osExit = myExit
Crasher()
if exp := 1; got != exp {
t.Errorf("Expected exit code: %d, got: %d", exp, got)
}
}
Running go test -cover
:
Going down in flames!
PASS
coverage: 100.0% of statements
ok foo 0.002s
Yes, you might say this works if os.Exit()
is called explicitly, but what if os.Exit()
is called by someone else, e.g. log.Fatalf()
?
The same technique works there too, you just have to switch log.Fatalf()
instead of os.Exit()
, e.g.:
Relevant part of foo/bar.go
:
var logFatalf = log.Fatalf
func Crasher() {
fmt.Println("Going down in flames!")
logFatalf("Exiting with code: %d", 1)
}
And the testing code: TestCrasher()
in foo/bar_test.go
:
func TestCrasher(t *testing.T) {
// Save current function and restore at the end:
oldLogFatalf := logFatalf
defer func() { logFatalf = oldLogFatalf }()
var gotFormat string
var gotV []interface{}
myFatalf := func(format string, v ...interface{}) {
gotFormat, gotV = format, v
}
logFatalf = myFatalf
Crasher()
expFormat, expV := "Exiting with code: %d", []interface{}{1}
if gotFormat != expFormat || !reflect.DeepEqual(gotV, expV) {
t.Error("Something went wrong")
}
}
Running go test -cover
:
Going down in flames!
PASS
coverage: 100.0% of statements
ok foo 0.002s