exec: enable tests on windows

Fixes #1104.

R=golang-dev, mattn, r
CC=Joe Poirier, golang-dev
https://golang.org/cl/3051041

src/pkg/Makefile

@@ -197,7 +197,6 @@ endif
 
 # Disable tests that windows cannot run yet.
 ifeq ($(GOOS),windows)
-NOTEST+=exec         # no pipe
 NOTEST+=os/signal    # no signals
 NOTEST+=path         # tree walking does not work
 NOTEST+=syslog       # no network

src/pkg/exec/exec_test.go

@@ -9,15 +9,23 @@ import (
 	"io/ioutil"
 	"testing"
 	"os"
+	"runtime"
 )
 
-func TestRunCat(t *testing.T) {
-	cat, err := LookPath("cat")
+func run(argv []string, stdin, stdout, stderr int) (p *Cmd, err os.Error) {
+	if runtime.GOOS == "windows" {
+		argv = append([]string{"cmd", "/c"}, argv...)
+	}
+	exe, err := LookPath(argv[0])
 	if err != nil {
-		t.Fatal("cat: ", err)
+		return nil, err
 	}
-	cmd, err := Run(cat, []string{"cat"}, nil, "",
-		Pipe, Pipe, DevNull)
+	p, err = Run(exe, argv, nil, "", stdin, stdout, stderr)
+	return p, err
+}
+
+func TestRunCat(t *testing.T) {
+	cmd, err := run([]string{"cat"}, Pipe, Pipe, DevNull)
 	if err != nil {
 		t.Fatal("run:", err)
 	}
@@ -36,11 +44,7 @@ func TestRunCat(t *testing.T) {
 }
 
 func TestRunEcho(t *testing.T) {
-	echo, err := LookPath("echo")
-	if err != nil {
-		t.Fatal("echo: ", err)
-	}
-	cmd, err := Run(echo, []string{"echo", "hello", "world"}, nil, "",
+	cmd, err := run([]string{"sh", "-c", "echo hello world"},
 		DevNull, Pipe, DevNull)
 	if err != nil {
 		t.Fatal("run:", err)
@@ -58,11 +62,7 @@ func TestRunEcho(t *testing.T) {
 }
 
 func TestStderr(t *testing.T) {
-	sh, err := LookPath("sh")
-	if err != nil {
-		t.Fatal("sh: ", err)
-	}
-	cmd, err := Run(sh, []string{"sh", "-c", "echo hello world 1>&2"}, nil, "",
+	cmd, err := run([]string{"sh", "-c", "echo hello world 1>&2"},
 		DevNull, DevNull, Pipe)
 	if err != nil {
 		t.Fatal("run:", err)
@@ -80,11 +80,7 @@ func TestStderr(t *testing.T) {
 }
 
 func TestMergeWithStdout(t *testing.T) {
-	sh, err := LookPath("sh")
-	if err != nil {
-		t.Fatal("sh: ", err)
-	}
-	cmd, err := Run(sh, []string{"sh", "-c", "echo hello world 1>&2"}, nil, "",
+	cmd, err := run([]string{"sh", "-c", "echo hello world 1>&2"},
 		DevNull, Pipe, MergeWithStdout)
 	if err != nil {
 		t.Fatal("run:", err)
@@ -106,11 +102,7 @@ func TestAddEnvVar(t *testing.T) {
 	if err != nil {
 		t.Fatal("setenv:", err)
 	}
-	sh, err := LookPath("sh")
-	if err != nil {
-		t.Fatal("sh: ", err)
-	}
-	cmd, err := Run(sh, []string{"sh", "-c", "echo $NEWVAR"}, nil, "",
+	cmd, err := run([]string{"sh", "-c", "echo $NEWVAR"},
 		DevNull, Pipe, DevNull)
 	if err != nil {
 		t.Fatal("run:", err)