diff --git a/npm/npm-test/action.yaml b/npm/npm-test/action.yaml
index 7eba525..47edd30 100644
--- a/npm/npm-test/action.yaml
+++ b/npm/npm-test/action.yaml
@@ -9,6 +9,14 @@ inputs:
     description: "Node.js version to use."
     required: false
     default: "20"
+  registries:
+    description: "Newline-separated list of registry URLs that require authentication."
+    required: false
+    default: "${{ github.server_url }}/api/packages/${{ github.repository_owner }}/npm/index.json"
+  apiKeys:
+    description: "Newline-separated list of API keys corresponding to registries."
+    required: false
+    default: "${{ github.token }}"
   testCommand:
     description: "Command to run tests. Default: npm test"
     required: false
@@ -50,6 +58,12 @@ runs:
       node-version: ${{ inputs.nodeVersion }}
       cache: npm
       cache-dependency-path: ${{ inputs.workingDirectory }}/package-lock.json
+  - name: "Configure npm authentication"
+    if: ${{ inputs.registries != '' && inputs.apiKeys != '' }}
+    run: |
+      bash "${{ github.action_path }}/configure-auth.sh" add "${{ inputs.registries }}" "${{ inputs.apiKeys }}"
+    working-directory: ${{ inputs.workingDirectory }}
+    shell: bash
   - name: "Install dependencies"
     run: npm ci
     working-directory: ${{ inputs.workingDirectory }}
@@ -74,3 +88,9 @@ runs:
       path: ${{ inputs.workingDirectory }}/${{ inputs.coverageDirectory }}
       if-no-files-found: warn
       retention-days: ${{ inputs.retention-days }}
+  - name: "Clean up npm authentication"
+    if: always()
+    run: |
+      bash "${{ github.action_path }}/configure-auth.sh" remove
+    working-directory: ${{ inputs.workingDirectory }}
+    shell: bash
diff --git a/npm/npm-test/configure-auth.sh b/npm/npm-test/configure-auth.sh
new file mode 100644
index 0000000..6926642
--- /dev/null
+++ b/npm/npm-test/configure-auth.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+set -e
+
+ACTION="$1"
+AUTH_URLS="$2"
+API_KEYS="$3"
+
+if [ "$ACTION" == "add" ]; then
+    # Parse newline-separated URLs and tokens into arrays
+    IFS=$'\n' read -rd '' -a URLS <<< "$AUTH_URLS" || true
+    IFS=$'\n' read -rd '' -a KEYS <<< "$API_KEYS" || true
+
+    # Verify arrays have matching lengths
+    if [ ${#URLS[@]} -ne ${#KEYS[@]} ]; then
+        echo "Error: Number of authUrls (${#URLS[@]}) does not match number of apiKeys (${#KEYS[@]})"
+        exit 1
+    fi
+
+    # Configure authentication for each registry
+    for i in "${!URLS[@]}"; do
+        URL="${URLS[$i]}"
+        KEY="${KEYS[$i]}"
+
+        # Skip empty entries
+        if [ -z "$URL" ] || [ -z "$KEY" ]; then
+            continue
+        fi
+
+        # Remove protocol from URL for npm config
+        REGISTRY_PATH=$(echo "$URL" | sed -E 's|https?://||')
+
+        echo "Configuring authentication for: $URL"
+        npm config set --location=project "//${REGISTRY_PATH}:_authToken" "$KEY"
+    done
+elif [ "$ACTION" == "remove" ]; then
+    # Clean up project .npmrc
+    rm -f .npmrc
+    echo "Removed npm authentication configuration"
+else
+    echo "Error: Invalid action '$ACTION'. Use 'add' or 'remove'"
+    exit 1
+fi