ensure stderr contains error reports (#29)

Signed-off-by: Alex Goodman <[email protected]>

application.go

@@ -270,7 +270,8 @@ func (a *application) Run() {
 	}()
 
 	if err := a.root.Execute(); err != nil {
-		color.Red.Println(strings.TrimSpace(err.Error()))
+		msg := color.Red.Render(strings.TrimSpace(err.Error()))
+		fmt.Fprintln(os.Stderr, msg)
 		exitCode = 1
 	}
 }

application_test.go

@@ -374,9 +374,17 @@ func Test_RunExitError(t *testing.T) {
 
 	cmd := exec.Command(os.Args[0], "-test.run=Test_RunExitError")
 	cmd.Env = append(os.Environ(), "CLIO_RUN_EXIT_ERROR=YES")
+
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
 	err := cmd.Run()
 	var e *exec.ExitError
 	if errors.As(err, &e) && !e.Success() {
+		// ensure that errors are reported to stderr, not stdout
+		assert.Contains(t, stderr.String(), "an error occurred")
+		assert.NotContains(t, stdout.String(), "an error occurred")
 		return
 	}
 	t.Fatalf("process ran with err %v, want exit status 1", err)