tests: add issue #9120 reproduction steps for run over ssh

tests/unit/run_2.bats

@@ -30,6 +30,26 @@ teardown() {
   assert_failure
 }
 
+@test "(run) run over ssh preserves echo-like arguments" {
+  run deploy_app
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "ssh dokku@$DOKKU_DOMAIN run $TEST_APP /bin/echo --version 2>/dev/null"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "--version"
+
+  # bats strips trailing newlines from $output, so count bytes to verify -n was honored
+  run /bin/bash -c "ssh dokku@$DOKKU_DOMAIN run $TEST_APP /bin/echo -n hello 2>/dev/null | wc -c"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "5"
+}
+
 @test "(run) run:detached" {
   run deploy_app
   echo "output: $output"