Use npm + package-lock.json

Author: ivome

.circleci/config.yml

@@ -21,12 +21,12 @@ jobs:
           # fallback to using the latest cache if no exact match is found
           - v1-dependencies-
 
-      - run: yarn install
+      - run: npm install
 
       - save_cache:
           paths:
             - node_modules
           key: v1-dependencies-{{ checksum "package.json" }}
 
       # run tests!
-      - run: yarn test
+      - run: npm test