Some small refactorings

tests/mock_genre_repo.go

@@ -0,0 +1,38 @@
+package tests
+
+import (
+	"github.com/navidrome/navidrome/model"
+)
+
+type MockedGenreRepo struct {
+	Error error
+	data  map[string]model.Genre
+}
+
+func (r *MockedGenreRepo) init() {
+	if r.data == nil {
+		r.data = make(map[string]model.Genre)
+	}
+}
+
+func (r *MockedGenreRepo) GetAll(...model.QueryOptions) (model.Genres, error) {
+	if r.Error != nil {
+		return nil, r.Error
+	}
+	r.init()
+
+	var all model.Genres
+	for _, g := range r.data {
+		all = append(all, g)
+	}
+	return all, nil
+}
+
+func (r *MockedGenreRepo) Put(g *model.Genre) error {
+	if r.Error != nil {
+		return r.Error
+	}
+	r.init()
+	r.data[g.ID] = *g
+	return nil
+}