Add to DarkModeViewModelTest

Make sure to test newly exposed variable in ag/30305049.

Flag: com.android.systemui.shared.new_customization_picker_ui
Test: unit test passes
Bug: 288312530
Change-Id: I5cfa9725f04d26afa4bad7c4b72971052657bb7c
diff --git a/tests/robotests/src/com/android/customization/picker/mode/ui/viewmodel/DarkModeViewModelTest.kt b/tests/robotests/src/com/android/customization/picker/mode/ui/viewmodel/DarkModeViewModelTest.kt
index 4078803..fbd56bc 100644
--- a/tests/robotests/src/com/android/customization/picker/mode/ui/viewmodel/DarkModeViewModelTest.kt
+++ b/tests/robotests/src/com/android/customization/picker/mode/ui/viewmodel/DarkModeViewModelTest.kt
@@ -91,16 +91,19 @@
         testScope.runTest {
             uiModeManager.setNightModeActivated(false)
             darkModeRepository.refreshIsDarkModeActivated()
+            val getOverridingIsDarkMode = collectLastValue(darkModeViewModel.overridingIsDarkMode)
             val getPreviewingIsDarkMode = collectLastValue(darkModeViewModel.previewingIsDarkMode)
             val getToggleDarkMode = collectLastValue(darkModeViewModel.toggleDarkMode)
             assertThat(getPreviewingIsDarkMode()).isFalse()
 
             getToggleDarkMode()?.invoke()
 
+            assertThat(getOverridingIsDarkMode()).isTrue()
             assertThat(getPreviewingIsDarkMode()).isTrue()
 
             getToggleDarkMode()?.invoke()
 
+            assertThat(getOverridingIsDarkMode()).isNull()
             assertThat(getPreviewingIsDarkMode()).isFalse()
         }
     }