test: improve tests for refute_stderr and refute_stderr_line

Author: mh182

test/refute_stderr.bats

@@ -159,7 +159,7 @@ ERR_MSG
 
 # Options
 @test 'refute_stderr() -e <regexp>: enables regular expression matching' {
-  run --separate-stderr echo_err 'abc'
+  run --separate-stderr echo_err 'abc^d'
   run refute_stderr -e '^d'
   assert_test_pass
 }

test/refute_stderr_line.bats

@@ -291,7 +291,7 @@ ERR_MSG
 # Options
 @test 'refute_stderr_line() --index <idx> -e <regexp>: enables regular expression matching' {
   run --separate-stderr printf_err 'a\nb\nc'
-  run refute_stderr_line --index 1 -e '^.b'
+  run refute_stderr_line --index 1 -e '[^.b]'
   assert_test_pass
 }