Backend: Add unit tests for internal/workers

internal/workers/sync_test.go

@@ -1,6 +1,7 @@
 package workers
 
 import (
+	"github.com/photoprism/photoprism/internal/mutex"
 	"testing"
 
 	"github.com/photoprism/photoprism/internal/config"
@@ -14,3 +15,29 @@ func TestNewSync(t *testing.T) {
 
 	assert.IsType(t, &Sync{}, worker)
 }
+
+func TestSync_Start(t *testing.T) {
+	conf := config.TestConfig()
+
+	worker := NewSync(conf)
+
+	assert.IsType(t, &Sync{}, worker)
+
+	if err := mutex.SyncWorker.Start(); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := worker.Start(); err == nil {
+		t.Fatal("error expected")
+	}
+
+	mutex.SyncWorker.Stop()
+
+	if err := worker.Start(); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := worker.Start(); err != nil {
+		t.Fatal(err)
+	}
+}