Run clippy on tests (#491)

Author: chitoku-k

.github/workflows/ci.yml

@@ -30,7 +30,7 @@ jobs:
         env:
           REVIEWDOG_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
-          cargo clippy --workspace --quiet --message-format=short --color=never 2>&1 |
+          cargo clippy --tests --workspace --quiet --message-format=short --color=never 2>&1 |
             reviewdog -f=clippy -reporter=github-pr-annotations -filter-mode=nofilter -fail-on-error -tee
   build:
     name: Build