error: items after a test module
  --> $DIR/auxiliary/submodule.rs:2:1
   |
LL | mod tests {}
   | ^^^^^^^^^
LL |
LL | fn in_submodule() {}
   | ^^^^^^^^^^^^^^^^^
   |
   = note: `-D clippy::items-after-test-module` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::items_after_test_module)]`

error: aborting due to previous error