Add linting steps and improve testing steps

scripts/ci.bash

@@ -3,6 +3,7 @@
 
 set -euo pipefail
 
+# This script assumes that yarn has already ran.
 function main() {
   cd "$(dirname "${0}")/.."
 
@@ -21,10 +22,6 @@ function main() {
     export PACKAGE="true"
   fi
 
-  if [[ -z ${SKIP_YARN:-} ]] ; then
-    yarn
-  fi
-
   yarn build
   yarn binary
   if [[ -n ${PACKAGE:-} ]] ; then