cmd/jiri/test_runcmd.go

// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

// This file contains helper functions related to running shell commands in tests.

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

// runCmd handles the boilerplate associated with running an exec.Cmd object.
// In particular, it handles wiring up the std{out,err} pipes, reading from them,
// and checking errors.  runCmd doesn't return error because errors are reported
// on the testing object.  runCmd returns the stdout and stderr as strings.
func runCmd(t *testing.T, cmd *exec.Cmd, failureExpected bool) (string, string) {
	// Make sure go is in the path.
	_, err := exec.LookPath(cmd.Path)
	if err != nil {
		t.Fatal(err)
	}

	// Wire up output pipes.
	stderr, err := cmd.StderrPipe()
	if err != nil {
		t.Fatal(err)
	}
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		t.Fatal(err)
	}

	// Using .Start() is required when fetching output from pipes.
	if err = cmd.Start(); err != nil {
		t.Fatal(err)
	}

	// Reading from pipes is required before calling .Wait().
	outBytes, err := io.ReadAll(stdout)
	if err != nil {
		t.Fatal(err)
	}
	errBytes, err := io.ReadAll(stderr)
	if err != nil {
		t.Fatal(err)
	}
	if len(outBytes) > 0 || len(errBytes) > 0 {
		t.Logf("Command (%s) has output\nFull command: %v\n", cmd.Path, cmd.Args)
	}
	if len(outBytes) > 0 {
		t.Logf("Stdout:\n%s\n", string(outBytes))
	}
	if len(errBytes) > 0 {
		t.Logf("Stderr:\n%s\n", string(errBytes))
	}

	// Wait for it...
	if err = cmd.Wait(); err != nil {
		if !failureExpected {
			t.Fatal(err)
		}
	}

	return string(outBytes), string(errBytes)
}

func runfunc(f func()) (string, string, error) {
	oldout, olderr := os.Stdout, os.Stderr
	defer func() {
		os.Stdout, os.Stderr = oldout, olderr
	}()

	reader, writer, err := os.Pipe()
	if err != nil {
		return "", "", err
	}
	errReader, errWriter, err := os.Pipe()
	if err != nil {
		return "", "", err
	}
	os.Stdout, os.Stderr = writer, errWriter

	f()

	writer.Close()
	errWriter.Close()

	var outbuf, errbuf bytes.Buffer
	io.Copy(&outbuf, reader)
	io.Copy(&errbuf, errReader)

	return outbuf.String(), errbuf.String(), nil
}