diff --git a/src/testdir/test_assert.vim b/src/testdir/test_assert.vim
index fb31478..298a6db 100644
--- a/src/testdir/test_assert.vim
+++ b/src/testdir/test_assert.vim
@@ -31,6 +31,10 @@
   call assert_equal(1, assert_equal('bar', s))
   call assert_match("Expected 'bar' but got 'foo'", v:errors[0])
   call remove(v:errors, 0)
+
+  call assert_equal('XxxxxxxxxxxxxxxxxxxxxxX', 'XyyyyyyyyyyyyyyyyyyyyyyyyyX')
+  call assert_match("Expected 'X\\\\\\[x occurs 21 times]X' but got 'X\\\\\\[y occurs 25 times]X'", v:errors[0])
+  call remove(v:errors, 0)
 endfunc
 
 func Test_assert_equalfile()