diff --git a/api/proto_test.go b/api/proto_test.go
new file mode 100644
index 0000000000000..3c9d09ccb5e27
--- /dev/null
+++ b/api/proto_test.go
@@ -0,0 +1,41 @@
+package api
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"testing"
+
+	moby_buildkit_v1_types "github.com/moby/buildkit/api/types"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+var record = flag.Bool("record", false, "record actual values as fixtures")
+
+func TestProto(t *testing.T) {
+	r := &moby_buildkit_v1_types.WorkerRecord{
+		ID: "hello",
+		Labels: map[string]string{
+			"a": "foo",
+			"b": "bar",
+			"c": "baz",
+		},
+	}
+	b, err := r.Marshal()
+	require.NoError(t, err)
+
+	assertProto(t, b, "WorkerRecord")
+}
+
+func assertProto(tb testing.TB, actual []byte, name string) {
+	path := fmt.Sprintf("testdata/%s.bin", name)
+	if *record {
+		err := os.WriteFile(path, actual, 0600)
+		require.NoError(tb, err)
+		return
+	}
+	expected, err := os.ReadFile(path)
+	require.NoError(tb, err)
+	assert.Equal(tb, expected, actual)
+}
diff --git a/api/testdata/WorkerRecord.bin b/api/testdata/WorkerRecord.bin
new file mode 100644
index 0000000000000..f1fa2fbd2a2e5
--- /dev/null
+++ b/api/testdata/WorkerRecord.bin
@@ -0,0 +1,5 @@
+
+hello
+
cbaz
+
bbar
+
afoo
\ No newline at end of file