cmd/gogio: groundwork for Windows e2e tests on Wine

First, move from debian unstable to testing, since sway was promoted to
testing as of earlier this week.

Second, use the --sync option when using xdotool to move an X11 mouse.
This makes the command block until the mouse has finished moving to the
specified location, removing a potential race with the following
'xdotool click' command.

Third, deduplicate some logic into driverBase: tempDir to create a
temporary directory within a test, and needPrograms to skip a test if
the required programs aren't available.

Lastly, split the code that starts the X11 server into a method, so that
the future Wine e2e driver can reuse it. Since Wine is tightly coupled
with X11, we can reuse a good part of the code, including the X11 server
and the xdotool mechanisms.

We also add a TODO to perhaps improve the handling of the app's output
under each of the e2e test cases.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>

cmd/gogio/x11_test.go

@@ -10,7 +10,6 @@ import (
 	"image"
 	"image/png"
 	"io"
-	"io/ioutil"
 	"math/rand"
 	"os"
 	"os/exec"
@@ -26,43 +25,8 @@ type X11TestDriver struct {
 }
 
 func (d *X11TestDriver) Start(path string, width, height int) {
-	// Pick a random display number between 1 and 100,000. Most machines
-	// will only be using :0, so there's only a 0.001% chance of two
-	// concurrent test runs to run into a conflict.
-	rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
-	d.display = fmt.Sprintf(":%d", rnd.Intn(100000)+1)
-
-	var xprog string
-	xflags := []string{
-		"-wr", // we want a white background; the default is black
-	}
-	if *headless {
-		xprog = "Xvfb" // virtual X server
-		xflags = append(xflags, "-screen", "0", fmt.Sprintf("%dx%dx24", width, height))
-	} else {
-		xprog = "Xephyr" // nested X server as a window
-		xflags = append(xflags, "-screen", fmt.Sprintf("%dx%d", width, height))
-	}
-	xflags = append(xflags, d.display)
-
-	for _, prog := range []string{
-		xprog,     // to run the X server
-		"scrot",   // to take screenshots
-		"xdotool", // to send input
-	} {
-		if _, err := exec.LookPath(prog); err != nil {
-			d.Skipf("%s needed to run", prog)
-		}
-	}
-
 	// First, build the app.
-	dir, err := ioutil.TempDir("", "gio-endtoend-x11")
-	if err != nil {
-		d.Fatal(err)
-	}
-	d.Cleanup(func() { os.RemoveAll(dir) })
-
-	bin := filepath.Join(dir, "red")
+	bin := filepath.Join(d.tempDir("gio-endtoend-x11"), "red")
 	flags := []string{"build", "-tags", "nowayland", "-o=" + bin}
 	if raceEnabled {
 		flags = append(flags, "-race")
@@ -76,43 +40,7 @@ func (d *X11TestDriver) Start(path string, width, height int) {
 	var wg sync.WaitGroup
 	d.Cleanup(wg.Wait)
 
-	// First, start the X server.
-	{
-		ctx, cancel := context.WithCancel(context.Background())
-		cmd := exec.CommandContext(ctx, xprog, xflags...)
-		combined := &bytes.Buffer{}
-		cmd.Stdout = combined
-		cmd.Stderr = combined
-		if err := cmd.Start(); err != nil {
-			d.Fatal(err)
-		}
-		d.Cleanup(cancel)
-		d.Cleanup(func() {
-			// Give it a chance to exit gracefully, cleaning up
-			// after itself. After 10ms, the deferred cancel above
-			// will signal an os.Kill.
-			cmd.Process.Signal(os.Interrupt)
-			time.Sleep(10 * time.Millisecond)
-		})
-
-		// Wait for the X server to be ready. The socket path isn't
-		// terribly portable, but that's okay for now.
-		withRetries(d.T, time.Second, func() error {
-			socket := fmt.Sprintf("/tmp/.X11-unix/X%s", d.display[1:])
-			_, err := os.Stat(socket)
-			return err
-		})
-
-		wg.Add(1)
-		go func() {
-			if err := cmd.Wait(); err != nil && ctx.Err() == nil {
-				// Print all output and error.
-				io.Copy(os.Stdout, combined)
-				d.Error(err)
-			}
-			wg.Done()
-		}()
-	}
+	d.startServer(wg, width, height)
 
 	// Then, start our program on the X server above.
 	{
@@ -155,6 +83,67 @@ func (d *X11TestDriver) Start(path string, width, height int) {
 	d.waitForFrame()
 }
 
+func (d *X11TestDriver) startServer(wg sync.WaitGroup, width, height int) {
+	// Pick a random display number between 1 and 100,000. Most machines
+	// will only be using :0, so there's only a 0.001% chance of two
+	// concurrent test runs to run into a conflict.
+	rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
+	d.display = fmt.Sprintf(":%d", rnd.Intn(100000)+1)
+
+	var xprog string
+	xflags := []string{
+		"-wr", // we want a white background; the default is black
+	}
+	if *headless {
+		xprog = "Xvfb" // virtual X server
+		xflags = append(xflags, "-screen", "0", fmt.Sprintf("%dx%dx24", width, height))
+	} else {
+		xprog = "Xephyr" // nested X server as a window
+		xflags = append(xflags, "-screen", fmt.Sprintf("%dx%d", width, height))
+	}
+	xflags = append(xflags, d.display)
+
+	d.needPrograms(
+		xprog,     // to run the X server
+		"scrot",   // to take screenshots
+		"xdotool", // to send input
+	)
+	ctx, cancel := context.WithCancel(context.Background())
+	cmd := exec.CommandContext(ctx, xprog, xflags...)
+	combined := &bytes.Buffer{}
+	cmd.Stdout = combined
+	cmd.Stderr = combined
+	if err := cmd.Start(); err != nil {
+		d.Fatal(err)
+	}
+	d.Cleanup(cancel)
+	d.Cleanup(func() {
+		// Give it a chance to exit gracefully, cleaning up
+		// after itself. After 10ms, the deferred cancel above
+		// will signal an os.Kill.
+		cmd.Process.Signal(os.Interrupt)
+		time.Sleep(10 * time.Millisecond)
+	})
+
+	// Wait for the X server to be ready. The socket path isn't
+	// terribly portable, but that's okay for now.
+	withRetries(d.T, time.Second, func() error {
+		socket := fmt.Sprintf("/tmp/.X11-unix/X%s", d.display[1:])
+		_, err := os.Stat(socket)
+		return err
+	})
+
+	wg.Add(1)
+	go func() {
+		if err := cmd.Wait(); err != nil && ctx.Err() == nil {
+			// Print all output and error.
+			io.Copy(os.Stdout, combined)
+			d.Error(err)
+		}
+		wg.Done()
+	}()
+}
+
 func (d *X11TestDriver) Screenshot() image.Image {
 	cmd := exec.Command("scrot", "--silent", "--overwrite", "/dev/stdout")
 	cmd.Env = []string{"DISPLAY=" + d.display}
@@ -184,7 +173,7 @@ func (d *X11TestDriver) xdotool(args ...interface{}) {
 }
 
 func (d *X11TestDriver) Click(x, y int) {
-	d.xdotool("mousemove", x, y)
+	d.xdotool("mousemove", "--sync", x, y)
 	d.xdotool("click", "1")
 
 	// Wait for the gio app to render after this click.