How to mock exec.Command for multiple unit tests in Go lang? -
i learnt unit testing functions uses exec.command() i.e., mocking exec.command(). went ahead added more unit cases, running issues of not able mock output different scenarios.
here sample code hello.go i'm trying test...
package main import ( "fmt" "os/exec" ) var execcommand = exec.command func printdate() ([]byte, error) { cmd := execcommand("date") out, err := cmd.combinedoutput() return out, err } func main() { fmt.printf("hello, world\n") fmt.println(printdate()) } below test code hello_test.go...
package main import ( "fmt" "os" "os/exec" "testing" ) var mockedexitstatus = 1 var mockeddate = "sun aug 20" var expdate = "sun aug 20" func fakeexeccommand(command string, args ...string) *exec.cmd { cs := []string{"-test.run=testhelperprocess", "--", command} cs = append(cs, args...) cmd := exec.command(os.args[0], cs...) cmd.env = []string{"go_want_helper_process=1"} return cmd } func testhelperprocess(t *testing.t) { if os.getenv("go_want_helper_process") != "1" { return } // println("mocked data:", mockeddate) fmt.fprintf(os.stdout, mockeddate) os.exit(mockedexitstatus) } func testprintdate(t *testing.t) { execcommand = fakeexeccommand defer func() { execcommand = exec.command }() out, err := printdate() print("std out: ", string(out)) if err != nil { t.errorf("expected nil error, got %#v", err) } if string(out) != expdate { t.errorf("expected %q, got %q", expdate, string(out)) } } func testprintdateunabletorunerror(t *testing.t) { execcommand = fakeexeccommand defer func() { execcommand = exec.command }() mockedexitstatus = 1 mockeddate = "unable run date command" expdate = "unable run date command" out, err := printdate() print("std out: ", string(out)) if err != nil { t.errorf("expected nil error, got %#v", err) } if string(out) != expdate { t.errorf("expected %q, got %q", expdate, string(out)) } } go test fails second test testprintdateunabletorunerror...
$ go test hello std out: sun aug 20std out: sun aug 20--- fail: testprintdatetomorrow (0.01s) hello_test.go:62: expected "unable run date command", got "sun aug 20" fail fail hello 0.017s even though i'm trying set global mockeddate value inside test case, it's still getting global value initialized with. is global value not getting set? or changes global var not getting updated in testhelperprocess?
based on code you've posted, mockeddate variable doesn't anything. neither test, nor call printdate() utilizing it, testprintdateunabletorunerror() test performs tests before it.
if add functionality printdate() function return string of "unable run date command" (when case), condition on line 62 pass. said, such checks should unnecessary, when have error in return values printdate(). if returned error non-nil, returned output string should expected invalid (or empty, "").
i can't tell how want printdate() fail, stands, there's no way return values you're expecting in testprintdateunabletorunerror().
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