patch 8.2.0174: various commands not completely tested

Problem:    Various commands not completely tested.
Solution:   Add more test cases. (Yegappan Lakshmanan, closes #5551)
diff --git a/src/testdir/test_global.vim b/src/testdir/test_global.vim
index bdeaf8e..044839f 100644
--- a/src/testdir/test_global.vim
+++ b/src/testdir/test_global.vim
@@ -18,3 +18,11 @@
   call assert_equal(['nothing', '++found', 'found bad', 'bad'], getline(1, 4))
   bwipe!
 endfunc
+
+func Test_global_error()
+  call assert_fails('g\\a', 'E10:')
+  call assert_fails('g', 'E148:')
+  call assert_fails('g/\(/y', 'E476:')
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab