Add examples/tests for "pkg/execpipe" (100% coverage!)

pkg/execpipe/execpipe_example_test.go

@@ -0,0 +1,26 @@
+package execpipe_test
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/docker-library/go-dockerlibrary/pkg/execpipe"
+)
+
+func Example() {
+	pipe, err := execpipe.RunCommand("go", "version")
+	if err != nil {
+		panic(err)
+	}
+	defer pipe.Close()
+
+	var buf bytes.Buffer
+	io.Copy(&buf, pipe)
+
+	fmt.Println(strings.SplitN(buf.String(), " version ", 2)[0])
+
+	// Output:
+	// go
+}

pkg/execpipe/execpipe_test.go

@@ -0,0 +1,31 @@
+package execpipe_test
+
+import (
+	"os"
+	"os/exec"
+	"testing"
+
+	"github.com/docker-library/go-dockerlibrary/pkg/execpipe"
+)
+
+func TestStdoutPipeError(t *testing.T) {
+	cmd := exec.Command("nothing", "really", "matters", "in", "the", "end")
+
+	// set "Stdout" so that "cmd.StdoutPipe" fails
+	// https://golang.org/src/os/exec/exec.go?s=16834:16883#L587
+	cmd.Stdout = os.Stdout
+
+	_, err := execpipe.Run(cmd)
+	if err == nil {
+		t.Errorf("Expected execpipe.Run to fail -- it did not")
+	}
+}
+
+func TestStartError(t *testing.T) {
+	// craft a definitely-invalid command so that "cmd.Start" fails
+	// https://golang.org/src/os/exec/exec.go?s=8739:8766#L303
+	_, err := execpipe.RunCommand("nothing-really-matters-in-the-end--bogus-command")
+	if err == nil {
+		t.Errorf("Expected execpipe.RunCommand to fail -- it did not")
+	}
+}