diff --git a/tests/checks/fish_config.fish b/tests/checks/fish_config.fish
index efc08c9ac..6a142f85d 100644
--- a/tests/checks/fish_config.fish
+++ b/tests/checks/fish_config.fish
@@ -52,8 +52,8 @@ grep '\S' $__fish_config_dir/functions/{fish_prompt,fish_right_prompt,fish_mode_
 echo yes | fish_config prompt save nim >/dev/null
 grep -q nim@Hattori $__fish_config_dir/functions/fish_prompt.fish ||
 echo 'failed to save prompt?'
-cat $__fish_config_dir/functions/fish_right_prompt.fish
-# CHECKERR: cat: {{.*}}/functions/fish_right_prompt.fish: No such file or directory
+not path is $__fish_config_dir/functions/fish_right_prompt.fish
+or echo "fish_right_prompt.fish ought to be deleted"
 cat $__fish_config_dir/functions/fish_mode_prompt.fish
 # CHECK: function fish_mode_prompt
 # CHECK: end
diff --git a/tests/checks/fish_delta.fish b/tests/checks/fish_delta.fish
index 0712ba55a..698ef7118 100644
--- a/tests/checks/fish_delta.fish
+++ b/tests/checks/fish_delta.fish
@@ -5,7 +5,8 @@ for path in fish_greeting fish_job_summary
     __fish_data_with_file functions/$path.fish \
         cat >$__fish_config_dir/functions/$path.fish
 end
-sed -i 's/$/ # Modified/' $__fish_config_dir/functions/fish_greeting.fish
+set -l tmp (sed 's/$/ # Modified/' $__fish_config_dir/functions/fish_greeting.fish)
+string join -- \n $tmp >$__fish_config_dir/functions/fish_greeting.fish
 
 fish_delta --no-diff --new |
     string match -r '.*\b(?:delta-test|fish_greeting|fish_job_summary)\b.*'