`BasedOn="{StaticResource SegmentToggle}"` resolves while the dictionary is being built, so a
forward reference fails at load with "Cannot find resource named 'SegmentToggle'". The style now
sits after SegmentToggle and SegmentLabel, where its base already exists.
Guard: ThemeResourceTests gains the ordering rule — within one dictionary, no StaticResource may
point at a key defined later in the same file. The existence check alone passed this, which is
exactly why the app died on launch while the tests were green.
Root cause of the unreliable test results this session: a stale `testhost` held ytLive.dll locked,
so builds silently kept the previous assembly (MSB3027 on copy). Killed it; the suite now rebuilds
and the two new facts actually run.
gramps
568586c541