Add test cases for highlight Preference click behavior

On large screen Activity embedding devices, Settings homepage
shows a highlighted Preference which is mapped to current
right pane.

For better UX, when users click again on a highlighted Preference,
it should not launch SubSettings.

Fix: 236275503
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.dashboard.DashboardFeatureProviderImplTest
Change-Id: I222c9b015fb090f359c3c9f4187823477920715b

src/com/android/settings/homepage/TopLevelSettings.java

@@ -30,6 +30,7 @@ import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.ViewGroup;
 
+import androidx.annotation.VisibleForTesting;
 import androidx.fragment.app.Fragment;
 import androidx.preference.Preference;
 import androidx.preference.PreferenceFragmentCompat;
@@ -72,6 +73,13 @@ public class TopLevelSettings extends DashboardFragment implements SplitLayoutLi
         setArguments(args);
     }
 
+    /** Dependency injection ctor only for testing. */
+    @VisibleForTesting
+    public TopLevelSettings(TopLevelHighlightMixin highlightMixin) {
+        this();
+        mHighlightMixin = highlightMixin;
+    }
+
     @Override
     protected int getPreferenceScreenResId() {
         return R.xml.top_level_settings;