patch 8.2.0866: not enough tests for buffer writing

Problem:    Not enough tests for buffer writing.
Solution:   Add more tests. Use CheckRunVimInTerminal in more places.
            (Yegappan Lakshmanan, closes #6167)
diff --git a/src/testdir/test_search.vim b/src/testdir/test_search.vim
index a3b6705..c2ba6c2 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -886,9 +886,7 @@
 endfunc
 
 func Test_incsearch_scrolling()
-  if !CanRunVimInTerminal()
-    throw 'Skipped: cannot make screendumps'
-  endif
+  CheckRunVimInTerminal
   call assert_equal(0, &scrolloff)
   call writefile([
 	\ 'let dots = repeat(".", 120)',