test: add basic integration tests

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/github.com/moby/buildkit/util/testutil/integration/registry.go

@@ -0,0 +1,109 @@
+package integration
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+func NewRegistry(dir string) (url string, cl func() error, err error) {
+	if err := lookupBinary("registry"); err != nil {
+		return "", nil, err
+	}
+
+	deferF := &multiCloser{}
+	cl = deferF.F()
+
+	defer func() {
+		if err != nil {
+			deferF.F()()
+			cl = nil
+		}
+	}()
+
+	if dir == "" {
+		tmpdir, err := os.MkdirTemp("", "test-registry")
+		if err != nil {
+			return "", nil, err
+		}
+		deferF.append(func() error { return os.RemoveAll(tmpdir) })
+		dir = tmpdir
+	}
+
+	if _, err := os.Stat(filepath.Join(dir, "config.yaml")); err != nil {
+		if !errors.Is(err, os.ErrNotExist) {
+			return "", nil, err
+		}
+		template := fmt.Sprintf(`version: 0.1
+loglevel: debug
+storage:
+    filesystem:
+        rootdirectory: %s
+http:
+    addr: 127.0.0.1:0
+`, filepath.Join(dir, "data"))
+
+		if err := os.WriteFile(filepath.Join(dir, "config.yaml"), []byte(template), 0600); err != nil {
+			return "", nil, err
+		}
+	}
+
+	cmd := exec.Command("registry", "serve", filepath.Join(dir, "config.yaml")) //nolint:gosec // test utility
+	rc, err := cmd.StderrPipe()
+	if err != nil {
+		return "", nil, err
+	}
+	stop, err := startCmd(cmd, nil)
+	if err != nil {
+		return "", nil, err
+	}
+	deferF.append(stop)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	url, err = detectPort(ctx, rc)
+	if err != nil {
+		return "", nil, err
+	}
+
+	return
+}
+
+func detectPort(ctx context.Context, rc io.ReadCloser) (string, error) {
+	r := regexp.MustCompile(`listening on 127\.0\.0\.1:(\d+)`)
+	s := bufio.NewScanner(rc)
+	found := make(chan struct{})
+	defer func() {
+		close(found)
+		go io.Copy(io.Discard, rc)
+	}()
+
+	go func() {
+		select {
+		case <-ctx.Done():
+			select {
+			case <-found:
+				return
+			default:
+				rc.Close()
+			}
+		case <-found:
+		}
+	}()
+
+	for s.Scan() {
+		res := r.FindSubmatch(s.Bytes())
+		if len(res) > 1 {
+			return "localhost:" + string(res[1]), nil
+		}
+	}
+	return "", errors.Errorf("no listening address found")
+}