merged from gramsrv upstream

internal/domain/client_session_test.go

@@ -0,0 +1,21 @@
+package domain
+
+import "testing"
+
+func TestClientSessionMetadataPreferredLanguage(t *testing.T) {
+	for _, test := range []struct {
+		name string
+		in   ClientSessionMetadata
+		want string
+	}{
+		{name: "lang code wins", in: ClientSessionMetadata{LangCode: "RU-ru", SystemLangCode: "en-US"}, want: "ru"},
+		{name: "system fallback", in: ClientSessionMetadata{SystemLangCode: "pt_BR"}, want: "pt"},
+		{name: "empty", in: ClientSessionMetadata{}, want: ""},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			if got := test.in.PreferredLanguage(); got != test.want {
+				t.Fatalf("PreferredLanguage() = %q, want %q", got, test.want)
+			}
+		})
+	}
+}