[ci] Run Jest tests in parallel

Signed-off-by: Tyler Smalley <tyler.smalley@elastic.co>

.buildkite/pipelines/hourly.yml

@@ -135,8 +135,9 @@ steps:
 
   - command: .buildkite/scripts/steps/test/jest.sh
     label: 'Jest Tests'
+    parallelism: 5
     agents:
-      queue: c2-16
+      queue: n2-4
     timeout_in_minutes: 120
     key: jest
 

.buildkite/pipelines/pull_request/base.yml

@@ -133,8 +133,9 @@ steps:
 
   - command: .buildkite/scripts/steps/test/jest.sh
     label: 'Jest Tests'
+    parallelism: 5
     agents:
-      queue: c2-16
+      queue: n2-4
     timeout_in_minutes: 120
     key: jest
 

.buildkite/scripts/steps/test/jest.sh

@@ -9,5 +9,5 @@ is_test_execution_step
 .buildkite/scripts/bootstrap.sh
 
 echo '--- Jest'
-checks-reporter-with-killswitch "Jest Unit Tests" \
-  node scripts/jest --ci --verbose --maxWorkers=10
+checks-reporter-with-killswitch "Jest Unit Tests $((BUILDKITE_PARALLEL_JOB+1))" \
+  .buildkite/scripts/steps/test/jest_parallel.sh

.buildkite/scripts/steps/test/jest_parallel.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+set -euo pipefail
+
+JOB=$BUILDKITE_PARALLEL_JOB
+JOB_COUNT=$BUILDKITE_PARALLEL_JOB_COUNT
+
+i=0
+find src x-pack packages -name jest.config.js | sort | while read config; do
+  if [ "$(($i % $JOB_COUNT))" -eq $JOB ]; then
+    echo "--- $ node scripts/jest --config $config"
+    node scripts/jest --config $config --runInBand
+  fi
+
+  ((i=i+1))
+done