Merge pull request #376 from heroku/yarn-ci

run tests with yarn if available

bin/test

 #!/usr/bin/env bash
 
-cd "$1" && npm test
+BUILD_DIR=${1:-}
+if yarn --version > /dev/null 2>&1; then
+  cd "$BUILD_DIR" && yarn test
+else
+  cd "$BUILD_DIR" && npm test
+fi

test/run

@@ -398,7 +398,7 @@ testDangerousRangeStar() {
   compile "dangerous-range-star"
   assertCaptured "Dangerous semver range"
   assertCaptured "Resolving node version * via semver.io"
-  assertCaptured "Downloading and installing node 6."
+  assertCaptured "Downloading and installing node 7."
   assertCapturedError
 }
 
@@ -406,14 +406,14 @@ testDangerousRangeGreaterThan() {
   compile "dangerous-range-greater-than"
   assertCaptured "Dangerous semver range"
   assertCaptured "Resolving node version >0.4 via semver.io"
-  assertCaptured "Downloading and installing node 6."
+  assertCaptured "Downloading and installing node 7."
   assertCapturedError
 }
 
 testRangeWithSpace() {
   compile "range-with-space"
   assertCaptured "Resolving node version >= 0.8.x via semver.io"
-  assertCaptured "Downloading and installing node 6."
+  assertCaptured "Downloading and installing node 7."
   assertCapturedSuccess
 }