3 files changed, 8 insertions, 4 deletions
diff --git a/test/old/testdir/test_expr.vim b/test/old/testdir/test_expr.vim
index d771234983..4cb8da8c74 100644
--- a/test/old/testdir/test_expr.vim
+++ b/test/old/testdir/test_expr.vim
@@ -155,7 +155,8 @@ func Test_strcharpart()
   END
   call CheckLegacyAndVim9Success(lines)
 
-  call assert_fails('echo strcharpart("", 0, 0, {})', ['E728:', 'E728:'])
+  call assert_fails('call strcharpart("", 0, 0, {})', ['E728:', 'E728:'])
+  call assert_fails('call strcharpart("", 0, 0, -1)', ['E1023:', 'E1023:'])
 endfunc
 
 func Test_getreg_empty_list()
diff --git a/test/old/testdir/test_functions.vim b/test/old/testdir/test_functions.vim
index 6ff21bc859..41a8610893 100644
--- a/test/old/testdir/test_functions.vim
+++ b/test/old/testdir/test_functions.vim
@@ -1097,6 +1097,7 @@ func Test_byteidx()
   call assert_fails("call byteidx([], 0)", 'E730:')
   call assert_fails("call byteidx('abc', [])", 'E745:')
   call assert_fails("call byteidx('abc', 0, {})", ['E728:', 'E728:'])
+  call assert_fails("call byteidx('abc', 0, -1)", ['E1023:', 'E1023:'])
 endfunc
 
 " Test for byteidxcomp() using a character index
@@ -1137,6 +1138,7 @@ func Test_byteidxcomp()
   call assert_fails("call byteidxcomp([], 0)", 'E730:')
   call assert_fails("call byteidxcomp('abc', [])", 'E745:')
   call assert_fails("call byteidxcomp('abc', 0, {})", ['E728:', 'E728:'])
+  call assert_fails("call byteidxcomp('abc', 0, -1)", ['E1023:', 'E1023:'])
 endfunc
 
 " Test for byteidx() using a UTF-16 index
@@ -1497,7 +1499,6 @@ func Test_utf16idx_from_charidx()
   " error cases
   call assert_equal(-1, utf16idx(v:_null_string, 0, v:true, v:true))
   call assert_fails('let l = utf16idx("ab", 0, v:false, [])', 'E1212:')
-  call assert_fails('echo strchars("", {})', ['E728:', 'E728:'])
 endfunc
 
 " Test for strutf16len()
diff --git a/test/old/testdir/test_utf8.vim b/test/old/testdir/test_utf8.vim
index e5f6d68720..00b060a9e2 100644
--- a/test/old/testdir/test_utf8.vim
+++ b/test/old/testdir/test_utf8.vim
@@ -29,8 +29,10 @@ func Test_strchars()
     call assert_equal(exp[i], strcharlen(inp[i]))
   endfor
 
-  call assert_fails("let v=strchars('abc', [])", 'E745:')
-  call assert_fails("let v=strchars('abc', 2)", 'E1023:')
+  call assert_fails("call strchars('abc', 2)", ['E1023:', 'E1023:'])
+  call assert_fails("call strchars('abc', -1)", ['E1023:', 'E1023:'])
+  call assert_fails("call strchars('abc', {})", ['E728:', 'E728:'])
+  call assert_fails("call strchars('abc', [])", ['E745:', 'E745:'])
 endfunc
 
 " Test for customlist completion