use yarn

.travis.yml

@@ -4,14 +4,12 @@ node_js:
   - "6"
   - "8"
   - "10"
-  - "11"
+  - "10"
 
-script: npm test
-before_install:
-  - npm config set spin false
+cache:
+  yarn: true
 
-install:
-  - node --version
-  - npm --version
-  - git --version
-  - npm install --no-optional
+before_install:
+  - curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version 1.13.0
+  - export PATH="$HOME/.yarn/bin:$PATH"
+  - yarn --version

appveyor.yml

@@ -17,17 +17,18 @@ install:
   - git rev-parse HEAD
   # Get the latest stable version of Node 0.STABLE.latest
   - ps: Install-Product node $env:nodejs_version
-  # Typical npm stuff.
-  - md C:\nc
-  - npm config set cache C:\nc
-  - npm version
-  - npm install
+  - choco install yarn --version=1.13.0
+  - appveyor-retry yarn
+  - appveyor-retry yarn add mocha-appveyor-reporter # must be installed locally.
+
+cache:
+  - '%LOCALAPPDATA%\Yarn'
 
 # Post-install test scripts.
 test_script:
   # Output useful info for debugging.
-  - npm version
-  - cmd: npm test
+  - git rev-parse HEAD
+  - cmd: yarn run test
 
 # Don't actually build.
 build: off