try to retry 3 times after unit test went wrong

Dockerfile

@@ -59,8 +59,7 @@ RUN npm install \
   && sudo rm -fr /tmp/* ~/.npm
 
 COPY . .
-RUN npm run test \
-  && npm run dist
+RUN ./script/safe-test.sh && npm run dist
 
 # Loading from node_modules Folders: https://nodejs.org/api/modules.html
 # If it is not found there, then it moves to the parent directory, and so on, until the root of the file system is reached.

script/safe-test.sh

+#!/usr/bin/env bash
+MAX_RETRY_NUM=3
+
+n=0
+npm test
+while ((n < MAX_RETRY_NUM && $? > 0))
+do
+  ((n++))
+  npm test
+done