update dockerfile to support test stage

Dockerfile

@@ -1,11 +1,22 @@
-FROM node:alpine as Build
-ENV NODE_ENV=production
+FROM node:alpine as files 
 WORKDIR /app
 
 COPY [ "package-lock.json", "package.json", "index.ts", "tsconfig.json", "./" ]
 COPY server ./server
 
+FROM files as proddependencies
+ENV NODE_ENV=production
 RUN npm ci --omit=dev
 
+FROM proddependencies as compile 
 RUN npm run build
 CMD ["npm","run","start"]
+
+FROM files as dependencies
+RUN npm ci
+
+FROM dependencies as test
+COPY jest.config.js .
+COPY tests ./tests
+
+RUN npm run test