[graphics/digikam] core/tests/widgets: Add ThemeManager unit test

Git commit ddb444176203c321542d87e867a184b468bca150 by Andreas Winther.
Committed on 18/07/2026 at 21:28.
Pushed by cgilles into branch 'master'.

Add ThemeManager unit test

Cover the public API contract that every method must be safe to call
before a theme menu has been registered with setThemeMenuAction().
Without the guard from the previous commit, updateThemeMenu() in that
state crashes with a null dereference of themeMenuActionGroup inside
updateCurrentDesktopDefaultThemePreview(), which this test catches as
a SIGSEGV. Also cover the default-theme fallback once a menu is
registered.

M  +1    -0    core/tests/widgets/CMakeLists.txt
A  +63   -0    core/tests/widgets/thememanager_utest.cpp     [License: GPL(v2.0+)]
A  +36   -0    core/tests/widgets/thememanager_utest.h     [License: GPL(v2.0+)]

https://invent.kde.org/graphics/digikam/-/commit/ddb444176203c321542d87e867a184b468bca150

diff --git a/core/tests/widgets/CMakeLists.txt b/core/tests/widgets/CMakeLists.txt
index 249f9c97c4..a4f7a9a68f 100644
--- a/core/tests/widgets/CMakeLists.txt
+++ b/core/tests/widgets/CMakeLists.txt
@@ -13,6 +13,7 @@ include_directories(
 ##################################################################
 
 ecm_add_tests(${CMAKE_CURRENT_SOURCE_DIR}/searchtextbar_utest.cpp
+              ${CMAKE_CURRENT_SOURCE_DIR}/thememanager_utest.cpp
 
               NAME_PREFIX
 
diff --git a/core/tests/widgets/thememanager_utest.cpp b/core/tests/widgets/thememanager_utest.cpp
new file mode 100644
index 0000000000..7741cf6950
--- /dev/null
+++ b/core/tests/widgets/thememanager_utest.cpp
@@ -0,0 +1,63 @@
+/* ============================================================
+ *
+ * This file is a part of digiKam project
+ * https://www.digikam.org
+ *
+ * Date        : 2026-07-18
+ * Description : a test for the theme manager
+ *
+ * SPDX-FileCopyrightText: 2026 by Andreas Winther <git dot tumble747 at simplelogin dot com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * ============================================================ */
+
+#include "thememanager_utest.h"
+
+// Qt includes
+
+#include <QMenu>
+#include <QTest>
+
+// Local includes
+
+#include "thememanager.h"
+
+using namespace Digikam;
+
+QTEST_MAIN(ThemeManagerTest)
+
+ThemeManagerTest::ThemeManagerTest(QObject* const parent)
+    : QObject(parent)
+{
+}
+
+void ThemeManagerTest::testCallsBeforeMenuRegistration()
+{
+    ThemeManager* const tm = ThemeManager::instance();
+
+    // Every public method must be safe to call before a theme menu
+    // has been registered with setThemeMenuAction().
+
+    QCOMPARE(tm->currentThemeName(), tm->defaultThemeName());
+
+    tm->setCurrentTheme(QLatin1String("Does Not Exist"));
+    QCOMPARE(tm->currentThemeName(), tm->defaultThemeName());
+
+    tm->updateThemeMenu();
+    QCOMPARE(tm->currentThemeName(), tm->defaultThemeName());
+}
+
+void ThemeManagerTest::testAfterMenuRegistration()
+{
+    ThemeManager* const tm = ThemeManager::instance();
+    QMenu menu;
+
+    tm->setThemeMenuAction(&menu);
+
+    QCOMPARE(tm->currentThemeName(), tm->defaultThemeName());
+    QVERIFY(!menu.actions().isEmpty());
+
+    tm->updateThemeMenu();
+    QCOMPARE(tm->currentThemeName(), tm->defaultThemeName());
+}
diff --git a/core/tests/widgets/thememanager_utest.h b/core/tests/widgets/thememanager_utest.h
new file mode 100644
index 0000000000..8d75487b30
--- /dev/null
+++ b/core/tests/widgets/thememanager_utest.h
@@ -0,0 +1,36 @@
+/* ============================================================
+ *
+ * This file is a part of digiKam project
+ * https://www.digikam.org
+ *
+ * Date        : 2026-07-18
+ * Description : a test for the theme manager
+ *
+ * SPDX-FileCopyrightText: 2026 by Andreas Winther <git dot tumble747 at simplelogin dot com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * ============================================================ */
+
+#ifndef DIGIKAM_THEME_MANAGER_UTEST_H
+#define DIGIKAM_THEME_MANAGER_UTEST_H
+
+// Qt includes
+
+#include <QObject>
+
+class ThemeManagerTest : public QObject
+{
+    Q_OBJECT
+
+public:
+
+    explicit ThemeManagerTest(QObject* const parent = nullptr);
+
+private Q_SLOTS:
+
+    void testCallsBeforeMenuRegistration();
+    void testAfterMenuRegistration();
+};
+
+#endif // DIGIKAM_THEME_MANAGER_UTEST_H