gh workflow: modify test.yml to have a conditional & only extract doc…

…ker tag if flag exists

.github/workflows/test.yml

@@ -73,11 +73,17 @@ jobs:
         with:
           node-version: 'lts/*'
           cache: npm
-      - name: Extract backend docker tags from PR body
+      - name: Extract Aerie backend docker tag from PR body
         # look in the PR body for eg. the string ___REQUIRES_AERIE_PR___=9999, extract the number & save to env var
         # if backend PR is labeled correctly, it will publish a docker tag called 'pr-9999' to use in tests
+        if: ${{ contains($PR_BODY, '___REQUIRES_AERIE_PR___=') }}
         run: |
           echo "AERIE_IMAGE_TAG=pr-$(echo $PR_BODY | sed -n 's/.*___REQUIRES_AERIE_PR___=\"\([0-9]\+\)\".*/\1/p')" >> $GITHUB_ENV
+      - name: Extract Aerie gateway docker tag from PR body
+        # look in the PR body for eg. the string ___REQUIRES_AERIE_PR___=9999, extract the number & save to env var
+        # if backend PR is labeled correctly, it will publish a docker tag called 'pr-9999' to use in tests
+        if: ${{ contains($PR_BODY, '___REQUIRES_GATEWAY_PR___=') }}
+        run: |
           echo "GATEWAY_IMAGE_TAG=pr-$(echo $PR_BODY | sed -n 's/.*___REQUIRES_GATEWAY_PR___=\"\([0-9]\+\)\".*/\1/p')" >> $GITHUB_ENV
       - name: Start Services (Aerie)
         run: |