Fix TestAttachExitCode

Signed-off-by: Daniel Nephin <dnephin@docker.com>

Author: dnephin

e2e/container/attach_test.go

@@ -1,17 +1,29 @@
 package container
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/gotestyourself/gotestyourself/icmd"
 )
 
 func TestAttachExitCode(t *testing.T) {
-	cName := "test-attach-exit-code"
-	icmd.RunCommand("docker", "run", "-d", "--rm", "--name", cName,
-		alpineImage, "sh", "-c", "sleep 5 ; exit 21").Assert(t, icmd.Success)
-	cmd := icmd.Command("docker", "wait", cName)
-	res := icmd.StartCmd(cmd)
-	icmd.RunCommand("docker", "attach", cName).Assert(t, icmd.Expected{ExitCode: 21})
-	icmd.WaitOnCmd(8, res).Assert(t, icmd.Expected{ExitCode: 0, Out: "21"})
+	containerID := runBackgroundContainsWithExitCode(t, 21)
+
+	result := icmd.RunCmd(
+		icmd.Command("docker", "attach", containerID),
+		withStdinNewline)
+
+	result.Assert(t, icmd.Expected{ExitCode: 21})
+}
+
+func runBackgroundContainsWithExitCode(t *testing.T, exitcode int) string {
+	result := icmd.RunCmd(shell(t,
+		"docker run -d -i --rm %s sh -c 'read; exit %d'", alpineImage, exitcode))
+	result.Assert(t, icmd.Success)
+	return strings.TrimSpace(result.Stdout())
+}
+
+func withStdinNewline(cmd *icmd.Cmd) {
+	cmd.Stdin = strings.NewReader("\n")
 }