use the same ref as ess-helm if it exists

.github/workflows/tests.yml

@@ -818,8 +818,27 @@ jobs:
       - name: Checkout
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
+      - name: Get current branch name
+        id: current-branch
+        run: echo "branch=${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}" >> $GITHUB_OUTPUT
+
+      - name: Check if branch exists in element-hq/ess-helm
+        id: check-branch
+        env:
+          BRANCH_NAME: ${{ steps.current-branch.outputs.branch }}
+        run: |
+          API_URL="https://api.github.com/repos/element-hq/ess-helm/branches/$BRANCH_NAME"
+          RESPONSE=$(curl -s -o /dev/null -w "%{http_code}" -H "Authorization: token ${{ secrets.GITHUB_TOKEN }}" $API_URL)
+          if [ "$RESPONSE" = "200" ]; then
+            echo "ref=$BRANCH_NAME" | tee -a $GITHUB_OUTPUT
+          else
+            echo "ref=main" | tee -a $GITHUB_OUTPUT
+          fi
+
       - name: Install ESS test dependencies
         uses: element-hq/setup-ess-cluster-action@release/v2
+        with:
+          ess-helm-ref: ${{ steps.check-branch.outputs.ref }}
 
       - name: Build Synapse docker image to local registry
         run: |