patch 8.2.0448: various functions not properly tested

Problem:    Various functions not properly tested.
Solution:   Add more tests, especially for failures. (Yegappan Lakshmanan,
            closes #5843)
diff --git a/src/testdir/test_search.vim b/src/testdir/test_search.vim
index c607a14..d57dbd7 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -1385,6 +1385,15 @@
   close!
 endfunc
 
+" Test for error cases with the search() function
+func Test_search_errors()
+  call assert_fails("call search('pat', [])", 'E730:')
+  call assert_fails("call search('pat', 'b', {})", 'E728:')
+  call assert_fails("call search('pat', 'b', 1, [])", 'E745:')
+  call assert_fails("call search('pat', 'ns')", 'E475:')
+  call assert_fails("call search('pat', 'mr')", 'E475:')
+endfunc
+
 func Test_search_display_pattern()
   new
   call setline(1, ['foo', 'bar', 'foobar'])