In vim tests check for printed messages

tests/test_local_overrides.vim

@@ -3,6 +3,9 @@ set encoding=utf-8
 let g:powerline_config_path = expand('<sfile>:p:h:h') . '/powerline/config_files'
 let g:powerline_config_overrides = {'common': {'default_top_theme': 'ascii'}}
 let g:powerline_theme_overrides__default = {'segment_data': {'line_current_symbol': {'contents': 'LN '}, 'branch': {'before': 'B '}}}
+
+redir => g:messages
+
 try
 	python import powerline.vim
 	let pycmd = 'python'
@@ -36,4 +39,10 @@ if result isnot# '%#Pl_22_24320_148_11523840_bold# NORMAL %#Pl_148_11523840_236_
 	cquit
 endif
 
+redir END
+if g:messages =~ '\S'
+	call writefile(['Non-empty messages:', g:messages], 'message.fail')
+	cquit
+endif
+
 qall!

tests/test_tabline.vim

@@ -6,6 +6,8 @@ edit abc
 tabedit def
 tabedit ghi
 
+redir => g:messages
+
 try
 	let &columns = 80
 	let result = eval(&tabline[2:])
@@ -45,4 +47,10 @@ if result isnot# '%#Pl_240_5789784_235_2500134_NONE# 1 %#Pl_240_5789784_235_25
 	cquit
 endif
 
+redir END
+if g:messages =~ '\S'
+	call writefile(['Non-empty messages:', g:messages], 'message.fail')
+	cquit
+endif
+
 qall!