Issue 5116/2: Add regtest

diff --git a/input/regression/nullvoice-change.ly b/input/regression/nullvoice-change.ly
new file mode 100644 (file)
index 0000000..c2835c7
--- /dev/null
+++ b/input/regression/nullvoice-change.ly
@@ -0,0 +1,29 @@
+\version "2.19.59"
+
+\header {
+  texidoc = "@samp{NullVoice} responds to @code{\\change Staff} as a
+@samp{Voice} would.  In consequence, in the first shown system
+it keeps a single treble-clef staff alive.  In the second
+system, it is in a single bass-clef staff."
+}
+
+\layout { ragged-right = ##t }
+
+music = \fixed c' {
+  c1
+  \break
+  \change Staff = "After"
+  c
+}
+
+\markup
+\score-lines {
+  \new StaffGroup \with \RemoveAllEmptyStaves
+  <<
+    \new Staff = "Before" \new NullVoice \music
+    \new Staff = "After" {
+      \clef bass
+      $(skip-of-length music)
+    }
+  >>
+}