diff --git a/.travis.yml b/.travis.yml
index 5864afd100865..1e76764065a73 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,5 @@
 language: node_js
-sudo: required  # See http://docs.travis-ci.com/user/trusty-ci-environment/
+sudo: false
 dist: trusty
 node_js:
   - "lts/*"
@@ -14,17 +14,14 @@ notifications:
   webhooks:
     - http://savage.nonblocking.io:8080/savage/travis
 before_install:
-  - export CHROME_BIN=google-chrome-stable
-  - export DISPLAY=:99.0
-  - unset _JAVA_OPTIONS  # JVM heap sizes break closure compiler. #11203.
-  - sh -e /etc/init.d/xvfb start
+  #- export CHROME_BIN=google-chrome-stable
+  #- export DISPLAY=:99.0
+  #- unset _JAVA_OPTIONS  # JVM heap sizes break closure compiler. #11203.
+  #- sh -e /etc/init.d/xvfb start
   - curl -o- -L https://yarnpkg.com/install.sh | bash
   - export PATH="$HOME/.yarn/bin:$HOME/.config/yarn/global/node_modules/.bin:$PATH"
-# before_script:
-#  - pip install --user protobuf
-# script: node build-system/pr-check.js
-# after_script:
-#   - build-system/sauce_connect/stop_sauce_connect.sh
+  - pip install urllib3[secure]
+  - pip install gsutil --user
 branches:
   only:
     - master
@@ -32,53 +29,72 @@ branches:
     - canary
     - /^amp-release-.*$/
     - /^revert-.*$/
-addons:
-  chrome: stable
-  hosts:
-    - ads.localhost
-    - iframe.localhost
-    # Requested by some tests because they need a valid font host,
-    # but should not resolve in tests.
-    - fonts.googleapis.com
-  apt:
-    packages:
-      - protobuf-compiler
-      - python-protobuf
 stages:
   - build
   - test
 jobs:
+  fast_finish: true
+  allowed_failures:
+    - stage: test
+      name: "Remote (Sauce Labs) Tests"
+      script:
+        - node build-system/pr-check/remote-test.js
+      after_script:
+        - build-system/sauce_connect/stop_sauce_connect.sh
   include:
     - stage: build
       name: "Build"
       script:
-        - node build-system/pr-check/build-job.js #TODO(estherkim)
-    # - stage: build
-    #   name: "Checks" 
-    #   script:
-    #     - node build-system/pr-check/checks-job.js #TODO(estherkim)
-    # - stage: build
-    #   name: "Validator"        
-    #   before_script:
-    #     - pip install --user protobuf #required by validator
-    #   script:
-    #     - node build-system/pr-check/validator-job.js #TODO(estherkim)
-    # - stage: test
-    #   name: "Dist, Bundle Size, Single Pass Tests"
-    #   script:
-    #     - node build-system/pr-check/dist-tests-job.js #TODO(estherkim)
-    # - stage: test
-    #   name: "Visual Diff Tests"
-    #   script:
-    #     - node build-system/pr-check/visual-diff-tests-job.js #TODO(estherkim)
-    # - stage: test
-    #   name: "Local Tests"
-    #   script:
-    #     - node build-system/pr-check/local-tests-job.js #TODO(estherkim)
-    # - stage: test
-    #   name: "Remote (Sauce Labs) Tests"
-    #   script:
-    #     - node build-system/pr-check/remote-tests-job.js #TODO(estherkim)
+        - node build-system/pr-check/build.js
+    - stage: build
+      name: "Checks" 
+      script:        
+        - node build-system/pr-check/checks.js
+    - stage: build
+      name: "Validator"        
+      before_script:
+        - pip install --user protobuf #required by validator
+      script:        
+        - node build-system/pr-check/validator.js
+      addons:
+        apt:
+          packages:
+            - protobuf-compiler
+            - python-protobuf
+    - stage: test
+      name: "Dist, Bundle Size, Single Pass Tests"
+      script:
+        - node build-system/pr-check/dist-test.js
+    - stage: test
+      name: "Visual Diff Tests"
+      script:
+        - node build-system/pr-check/visual-diff-test.js
+    - stage: test
+      name: "Local Tests"
+      before_install: 
+        - export CHROME_BIN=google-chrome-stable
+        - export DISPLAY=:99.0
+        # Explicitly add yarn and gsutil install because this section overrides before_install parent section
+        - curl -o- -L https://yarnpkg.com/install.sh | bash
+        - export PATH="$HOME/.yarn/bin:$HOME/.config/yarn/global/node_modules/.bin:$PATH"
+        - pip install urllib3[secure]
+        - pip install gsutil --user
+      addons:
+        chrome: stable
+        hosts:
+          - ads.localhost
+          - iframe.localhost
+          # Requested by some tests because they need a valid font host,
+          # but should not resolve in tests.
+          - fonts.googleapis.com
+      script:
+        - node build-system/pr-check/local-test.js
+    - stage: test
+      name: "Remote (Sauce Labs) Tests"
+      script:
+        - node build-system/pr-check/remote-test.js
+      after_script:
+        - build-system/sauce_connect/stop_sauce_connect.sh
 cache:
   yarn: true
   directories:
diff --git a/build-system/pr-check/build-job.js b/build-system/pr-check/build-job.js
deleted file mode 100644
index 91df21a86ac0f..0000000000000
--- a/build-system/pr-check/build-job.js
+++ /dev/null
@@ -1,204 +0,0 @@
-/**
- * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS-IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-'use strict';
-
-/**
- * @fileoverview This file is executed by Travis (configured via
- * .travis.yml in the root directory) and is the main driver script
- * for running tests.  Execution herein is entirely synchronous, that
- * is, commands are executed on after the other (see the exec
- * function). Should a command fail, this script will then also fail.
- * This script attempts to introduce some granularity for our
- * presubmit checking, via the determineBuildTargets method.
- */
-const colors = require('ansi-colors');
-const command = require('./command');
-const {
-  determineBuildTargets,
-  isFlagConfig,
-} = require('./build-target');
-const {
-  gitBranchName,
-  gitDiffColor,
-  gitDiffCommitLog,
-  gitDiffNameOnlyMaster,
-  gitDiffStatMaster,
-  gitMergeBaseMaster,
-  gitTravisMasterBaseline,
-  shortSha,
-} = require('../git');
-const {
-  isTravisBuild,
-  isTravisPullRequestBuild,
-  isTravisPushBuild,
-  travisPullRequestSha,
-} = require('../travis');
-
-const {getStderr} = require('../exec');
-
-const fileLogPrefix = colors.bold(colors.yellow(fileName));
-const fileName = 'build-job.js';
-/**
- * Starts a timer to measure the execution time of the given function.
- * @param {string} functionName
- * @return {DOMHighResTimeStamp}
- */
-function startTimer(functionName) {
-  const startTime = Date.now();
-  console.log(
-      '\n' + fileLogPrefix, 'Running', colors.cyan(functionName) + '...');
-  return startTime;
-}
-
-/**
- * Stops the timer for the given function and prints the execution time.
- * @param {string} functionName
- * @param {DOMHighResTimeStamp} startTime
- * @return {number}
- */
-function stopTimer(functionName, startTime) {
-  const endTime = Date.now();
-  const executionTime = new Date(endTime - startTime);
-  const mins = executionTime.getMinutes();
-  const secs = executionTime.getSeconds();
-  console.log(
-      fileLogPrefix, 'Done running', colors.cyan(functionName),
-      'Total time:', colors.green(mins + 'm ' + secs + 's'));
-}
-
-/**
- * Prints a summary of files changed by, and commits included in the PR.
- */
-function printChangeSummary() {
-  if (isTravisBuild()) {
-    console.log(fileLogPrefix, colors.cyan('origin/master'),
-        'is currently at commit',
-        colors.cyan(shortSha(gitTravisMasterBaseline())));
-    console.log(fileLogPrefix,
-        'Testing the following changes at commit',
-        colors.cyan(shortSha(travisPullRequestSha())));
-  }
-
-  const filesChanged = gitDiffStatMaster();
-  console.log(filesChanged);
-
-  const branchPoint = gitMergeBaseMaster();
-  console.log(fileLogPrefix, 'Commit log since branch',
-      colors.cyan(gitBranchName()), 'was forked from',
-      colors.cyan('master'), 'at', colors.cyan(shortSha(branchPoint)) + ':');
-  console.log(gitDiffCommitLog() + '\n');
-}
-
-/**
- * Makes sure package.json and yarn.lock are in sync.
- */
-function runYarnIntegrityCheck() {
-  const yarnIntegrityCheck = getStderr('yarn check --integrity').trim();
-  if (yarnIntegrityCheck.includes('error')) {
-    console.error(fileLogPrefix, colors.red('ERROR:'),
-        'Found the following', colors.cyan('yarn'), 'errors:\n' +
-        colors.cyan(yarnIntegrityCheck));
-    console.error(fileLogPrefix, colors.red('ERROR:'),
-        'Updates to', colors.cyan('package.json'),
-        'must be accompanied by a corresponding update to',
-        colors.cyan('yarn.lock'));
-    console.error(fileLogPrefix, colors.yellow('NOTE:'),
-        'To update', colors.cyan('yarn.lock'), 'after changing',
-        colors.cyan('package.json') + ',', 'run',
-        '"' + colors.cyan('yarn install') + '"',
-        'and include the updated', colors.cyan('yarn.lock'),
-        'in your PR.');
-    process.exit(1);
-  }
-}
-
-/**
- * Makes sure that yarn.lock was properly updated.
- */
-function runYarnLockfileCheck() {
-  const localChanges = gitDiffColor();
-  if (localChanges.includes('yarn.lock')) {
-    console.error(fileLogPrefix, colors.red('ERROR:'),
-        'This PR did not properly update', colors.cyan('yarn.lock') + '.');
-    console.error(fileLogPrefix, colors.yellow('NOTE:'),
-        'To fix this, sync your branch to', colors.cyan('upstream/master') +
-        ', run', colors.cyan('gulp update-packages') +
-        ', and push a new commit containing the changes.');
-    console.error(fileLogPrefix, 'Expected changes:');
-    console.log(localChanges);
-    process.exit(1);
-  }
-}
-
-/**
- * The main method for the script execution which much like a C main function
- * receives the command line arguments and returns an exit status.
- * @return {number}
- */
-function main() {
-  const startTime = startTimer(fileName);
-
-  // Make sure package.json and yarn.lock are in sync and up-to-date.
-  runYarnIntegrityCheck();
-  runYarnLockfileCheck();
-
-  console.log(
-      fileLogPrefix, 'Running build shard',
-      colors.cyan(process.env.BUILD_SHARD),
-      '\n');
-
-  printChangeSummary();
-  const files = gitDiffNameOnlyMaster();
-  const buildTargets = determineBuildTargets(files);
-
-  // Exit early if flag-config files are mixed with runtime files.
-  if (buildTargets.has('FLAG_CONFIG') && buildTargets.has('RUNTIME')) {
-    console.log(fileLogPrefix, colors.red('ERROR:'),
-        'Looks like your PR contains',
-        colors.cyan('{prod|canary}-config.json'),
-        'in addition to some other files.  Config and code are not kept in',
-        'sync, and config needs to be backwards compatible with code for at',
-        'least two weeks.  See #8188');
-    const nonFlagConfigFiles = files.filter(file => !isFlagConfig(file));
-    console.log(fileLogPrefix, colors.red('ERROR:'),
-        'Please move these files to a separate PR:',
-        colors.cyan(nonFlagConfigFiles.join(', ')));
-    stopTimer(fileName, startTime);
-    process.exit(1);
-  }
-
-  console.log(
-      fileLogPrefix, 'Detected build targets:',
-      colors.cyan(Array.from(buildTargets).sort().join(', ')));
-
-  if (isTravisPullRequestBuild()) {
-    command.updatePackages();
-    if (buildTargets.has('BUILD_SYSTEM') ||
-        buildTargets.has('RUNTIME')) {
-      command.testBuildSystem();
-    }
-  } else if (isTravisPushBuild()) {
-    command.updatePackages();
-    command.testBuildSystem();
-    command.cleanBuild();
-    command.buildRuntime();
-  }
-
-  stopTimer(fileName, startTime);
-  return 0;
-}
-
-process.exit(main());
diff --git a/build-system/pr-check/build-target.js b/build-system/pr-check/build-target.js
index 102782cf59bd0..45806e2111302 100644
--- a/build-system/pr-check/build-target.js
+++ b/build-system/pr-check/build-target.js
@@ -24,9 +24,10 @@
  * This script attempts to introduce some granularity for our
  * presubmit checking, via the determineBuildTargets method.
  */
-const config = require('./config');
+const config = require('../config');
 const minimatch = require('minimatch');
 const path = require('path');
+const {gitDiffNameOnlyMaster} = require('../git');
 
 /**
  * Determines whether the given file belongs to the Validator webui,
@@ -186,10 +187,11 @@ function isFlagConfig(filePath) {
 /**
  * Determines the targets that will be executed by the main method of
  * this script. The order within this function matters.
- * @param {!Array<string>} filePaths
  * @return {!Set<string>}
  */
-function determineBuildTargets(filePaths) {
+function determineBuildTargets() {
+  const filePaths = gitDiffNameOnlyMaster();
+
   if (filePaths.length == 0) {
     return new Set([
       'BUILD_SYSTEM',
diff --git a/build-system/pr-check/build.js b/build-system/pr-check/build.js
new file mode 100644
index 0000000000000..b39150d2f798e
--- /dev/null
+++ b/build-system/pr-check/build.js
@@ -0,0 +1,141 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+/**
+ * @fileoverview
+ * This script builds the AMP runtime.
+ * This is run during the CI stage = build; job = build.
+ */
+
+//TODO(estherkim): move to util file
+const colors = require('ansi-colors');
+const {
+  gitBranchName,
+  gitDiffColor,
+  gitDiffCommitLog,
+  gitDiffStatMaster,
+  gitMergeBaseMaster,
+  gitTravisMasterBaseline,
+  shortSha,
+} = require('../git');
+const {
+  isTravisBuild,
+  travisPullRequestSha,
+} = require('../travis');
+const {determineBuildTargets} = require('./build-target');
+const {getStderr} = require('../exec');
+const {startTimer, stopTimer, timedExecOrDie, zipBuildOutput} = require('./utils');
+
+const FILENAME = 'build.js';
+const FILELOGPREFIX = colors.bold(colors.yellow(`${FILENAME}:`));
+
+/**
+ * Prints a summary of files changed by, and commits included in the PR.
+ */
+function printChangeSummary_() {
+  if (isTravisBuild()) {
+    console.log(FILELOGPREFIX, colors.cyan('origin/master'),
+        'is currently at commit',
+        colors.cyan(shortSha(gitTravisMasterBaseline())));
+    console.log(FILELOGPREFIX,
+        'Testing the following changes at commit',
+        colors.cyan(shortSha(travisPullRequestSha())));
+  }
+
+  const filesChanged = gitDiffStatMaster();
+  console.log(filesChanged);
+
+  const branchPoint = gitMergeBaseMaster();
+  console.log(FILELOGPREFIX, 'Commit log since branch',
+      colors.cyan(gitBranchName()), 'was forked from',
+      colors.cyan('master'), 'at', colors.cyan(shortSha(branchPoint)) + ':');
+  console.log(gitDiffCommitLog() + '\n');
+}
+
+/**
+ * Makes sure package.json and yarn.lock are in sync.
+ * @private
+ */
+function runYarnIntegrityCheck_() {
+  const yarnIntegrityCheck = getStderr('yarn check --integrity').trim();
+  if (yarnIntegrityCheck.includes('error')) {
+    console.error(FILELOGPREFIX, colors.red('ERROR:'),
+        'Found the following', colors.cyan('yarn'), 'errors:\n' +
+        colors.cyan(yarnIntegrityCheck));
+    console.error(FILELOGPREFIX, colors.red('ERROR:'),
+        'Updates to', colors.cyan('package.json'),
+        'must be accompanied by a corresponding update to',
+        colors.cyan('yarn.lock'));
+    console.error(FILELOGPREFIX, colors.yellow('NOTE:'),
+        'To update', colors.cyan('yarn.lock'), 'after changing',
+        colors.cyan('package.json') + ',', 'run',
+        '"' + colors.cyan('yarn install') + '"',
+        'and include the updated', colors.cyan('yarn.lock'),
+        'in your PR.');
+    process.exit(1);
+  }
+}
+
+/**
+ * Makes sure that yarn.lock was properly updated.
+ * @private
+ */
+function runYarnLockfileCheck_() {
+  const localChanges = gitDiffColor();
+  if (localChanges.includes('yarn.lock')) {
+    console.error(FILELOGPREFIX, colors.red('ERROR:'),
+        'This PR did not properly update', colors.cyan('yarn.lock') + '.');
+    console.error(FILELOGPREFIX, colors.yellow('NOTE:'),
+        'To fix this, sync your branch to', colors.cyan('upstream/master') +
+        ', run', colors.cyan('gulp update-packages') +
+        ', and push a new commit containing the changes.');
+    console.error(FILELOGPREFIX, 'Expected changes:');
+    console.log(localChanges);
+    process.exit(1);
+  }
+}
+
+function main() {
+  const startTime = startTimer(FILENAME);
+
+  // Make sure package.json and yarn.lock are in sync and up-to-date.
+  runYarnIntegrityCheck_();
+  runYarnLockfileCheck_();
+  printChangeSummary_();
+  const buildTargets = determineBuildTargets();
+
+  if (buildTargets.has('RUNTIME') ||
+        buildTargets.has('UNIT_TEST') ||
+        buildTargets.has('INTEGRATION_TEST') ||
+        buildTargets.has('BUILD_SYSTEM')) {
+
+    timedExecOrDie('gulp update-packages');
+    timedExecOrDie('gulp css');
+    timedExecOrDie('gulp build --fortesting');
+
+    zipBuildOutput();
+  } else {
+    console.log('Skipping build job because this commit does ' +
+     'not affect the runtime, build system, or test files');
+  }
+
+  stopTimer(FILENAME, startTime);
+  return 0;
+}
+
+process.exit(main());
+
diff --git a/build-system/pr-check/checks.js b/build-system/pr-check/checks.js
new file mode 100644
index 0000000000000..1c93faf1b66d7
--- /dev/null
+++ b/build-system/pr-check/checks.js
@@ -0,0 +1,73 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+/**
+ * @fileoverview
+ * This script performs quick checks on the source code
+ * prior to running unit and integration tests.
+ * This is run during the CI stage = build; job = checks.
+ */
+
+const {determineBuildTargets} = require('./build-target');
+const {isTravisPushBuild} = require('../travis');
+const {startTimer, stopTimer, timedExecOrDie} = require('./utils');
+
+const FILENAME = 'checks.js';
+
+function main() {
+  const startTime = startTimer(FILENAME);
+  const buildTargets = determineBuildTargets();
+
+  timedExecOrDie('gulp update-packages');
+  timedExecOrDie('gulp presubmit');
+  timedExecOrDie('gulp lint');
+
+  if (isTravisPushBuild()) {
+    timedExecOrDie('gulp ava');
+    timedExecOrDie('node node_modules/jest/bin/jest.js');
+    timedExecOrDie('gulp check-types');
+    timedExecOrDie('gulp caches-json');
+    timedExecOrDie('gulp json-syntax');
+    timedExecOrDie('gulp dep-check');
+  }
+  else {
+    if (buildTargets.has('RUNTIME') ||
+    buildTargets.has('BUILD_SYSTEM')) {
+      timedExecOrDie('gulp ava');
+      timedExecOrDie('node node_modules/jest/bin/jest.js');
+    }
+
+    if (buildTargets.has('RUNTIME') ||
+    buildTargets.has('BUILD_SYSTEM') ||
+    buildTargets.has('UNIT_TEST') ||
+    buildTargets.has('INTEGRATION_TEST')) {
+      timedExecOrDie('gulp check-types');
+      timedExecOrDie('gulp caches-json');
+      timedExecOrDie('gulp json-syntax');
+      timedExecOrDie('gulp dep-check');
+    }
+
+    if (buildTargets.has('DOCS')) {
+      timedExecOrDie('gulp check-links');
+    }
+  }
+
+  stopTimer(FILENAME, startTime);
+  return 0;
+}
+
+process.exit(main());
diff --git a/build-system/pr-check/command.js b/build-system/pr-check/command.js
deleted file mode 100644
index 4d4cd71fc85ca..0000000000000
--- a/build-system/pr-check/command.js
+++ /dev/null
@@ -1,212 +0,0 @@
-/**
- * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS-IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-'use strict';
-
-/**
- * @fileoverview This file is executed by Travis (configured via
- * .travis.yml in the root directory) and is the main driver script
- * for running tests.  Execution herein is entirely synchronous, that
- * is, commands are executed on after the other (see the exec
- * function). Should a command fail, this script will then also fail.
- * This script attempts to introduce some granularity for our
- * presubmit checking, via the determineBuildTargets method.
- */
-const argv = require('minimist')(process.argv.slice(2));
-const atob = require('atob');
-const colors = require('ansi-colors');
-const {execOrDie, exec, getStdout} = require('./exec');
-const fileLogPrefix = colors.bold(colors.yellow(fileName));
-const fileName = 'command.js';
-function startTimer(functionName) {
-  const startTime = Date.now();
-  console.log(
-      '\n' + fileLogPrefix, 'Running', colors.cyan(functionName) + '...');
-  return startTime;
-}
-
-/**
- * Stops the timer for the given function and prints the execution time.
- * @param {string} functionName
- * @param {DOMHighResTimeStamp} startTime
- * @return {number}
- */
-function stopTimer(functionName, startTime) {
-  const endTime = Date.now();
-  const executionTime = new Date(endTime - startTime);
-  const mins = executionTime.getMinutes();
-  const secs = executionTime.getSeconds();
-  console.log(
-      fileLogPrefix, 'Done running', colors.cyan(functionName),
-      'Total time:', colors.green(mins + 'm ' + secs + 's'));
-}
-
-/**
- * Executes the provided command and times it. Errors, if any, are printed.
- * @param {string} cmd
- * @return {<Object>} Process info.
- */
-function timedExec(cmd) {
-  const startTime = startTimer(cmd);
-  const p = exec(cmd);
-  stopTimer(cmd, startTime);
-  return p;
-}
-
-/**
- * Executes the provided command and times it. The program terminates in case of
- * failure.
- * @param {string} cmd
- */
-function timedExecOrDie(cmd) {
-  const startTime = startTimer(cmd);
-  execOrDie(cmd);
-  stopTimer(cmd, startTime);
-}
-
-function startSauceConnect() {
-  process.env['SAUCE_USERNAME'] = 'amphtml';
-  process.env['SAUCE_ACCESS_KEY'] = getStdout('curl --silent ' +
-      'https://amphtml-sauce-token-dealer.appspot.com/getJwtToken').trim();
-  const startScCmd = 'build-system/sauce_connect/start_sauce_connect.sh';
-  console.log('\n' + fileLogPrefix,
-      'Starting Sauce Connect Proxy:', colors.cyan(startScCmd));
-  execOrDie(startScCmd);
-}
-
-function stopSauceConnect() {
-  const stopScCmd = 'build-system/sauce_connect/stop_sauce_connect.sh';
-  console.log('\n' + fileLogPrefix,
-      'Stopping Sauce Connect Proxy:', colors.cyan(stopScCmd));
-  execOrDie(stopScCmd);
-}
-
-const command = {
-  testBuildSystem: function() {
-    timedExecOrDie('gulp ava');
-    timedExecOrDie('node node_modules/jest/bin/jest.js');
-  },
-  testDocumentLinks: function() {
-    timedExecOrDie('gulp check-links');
-  },
-  cleanBuild: function() {
-    timedExecOrDie('gulp clean');
-  },
-  runLintCheck: function() {
-    timedExecOrDie('gulp lint');
-  },
-  runJsonCheck: function() {
-    timedExecOrDie('gulp caches-json');
-    timedExecOrDie('gulp json-syntax');
-  },
-  buildCss: function() {
-    timedExecOrDie('gulp css');
-  },
-  buildRuntime: function() {
-    timedExecOrDie('gulp build --fortesting');
-  },
-  buildRuntimeMinified: function(extensions) {
-    let cmd = 'gulp dist --fortesting';
-    if (!extensions) {
-      cmd = cmd + ' --noextensions';
-    }
-    timedExecOrDie(cmd);
-  },
-  runBundleSizeCheck: function(action) {
-    timedExecOrDie(`gulp bundle-size --on_${action}_build`);
-  },
-  runDepAndTypeChecks: function() {
-    timedExecOrDie('gulp dep-check');
-    timedExecOrDie('gulp check-types');
-  },
-  runUnitTests: function() {
-    let cmd = 'gulp test --unit --nobuild';
-    if (argv.files) {
-      cmd = cmd + ' --files ' + argv.files;
-    }
-    // Unit tests with Travis' default chromium in coverage mode.
-    timedExecOrDie(cmd + ' --headless --coverage');
-
-    cmd = cmd + ' --saucelabs_lite';
-    startSauceConnect();
-    timedExecOrDie(cmd);
-    stopSauceConnect();
-  },
-  runUnitTestsOnLocalChanges: function() {
-    timedExecOrDie('gulp test --nobuild --headless --local-changes');
-  },
-  runDevDashboardTests: function() {
-    timedExecOrDie('gulp test --dev_dashboard --nobuild');
-  },
-  runIntegrationTests: function(compiled, coverage) {
-    // Integration tests on chrome, or on all saucelabs browsers if set up
-    let cmd = 'gulp test --integration --nobuild';
-    if (argv.files) {
-      cmd = cmd + ' --files ' + argv.files;
-    }
-    if (compiled) {
-      cmd += ' --compiled';
-    }
-
-    if (coverage) {
-      // TODO(choumx, #19658): --headless disabled for integration tests on
-      // Travis until Chrome 72.
-      timedExecOrDie(cmd + ' --coverage');
-    } else {
-      startSauceConnect();
-      timedExecOrDie(cmd + ' --saucelabs');
-      stopSauceConnect();
-    }
-  },
-  runSinglePassCompiledIntegrationTests: function() {
-    timedExecOrDie('rm -R dist');
-    timedExecOrDie('gulp dist --fortesting --single_pass --pseudo_names');
-    // TODO(choumx, #19658): --headless disabled for integration tests on
-    // Travis until Chrome 72.
-    timedExecOrDie('gulp test --integration --nobuild '
-        + '--compiled --single_pass');
-    timedExecOrDie('rm -R dist');
-  },
-  runVisualDiffTests: function(opt_mode) {
-    process.env['PERCY_TOKEN'] = atob(process.env.PERCY_TOKEN_ENCODED);
-    let cmd = 'gulp visual-diff --nobuild';
-    if (opt_mode === 'empty') {
-      cmd += ' --empty';
-    } else if (opt_mode === 'master') {
-      cmd += ' --master';
-    }
-    const {status} = timedExec(cmd);
-    if (status != 0) {
-      console.error(fileLogPrefix, colors.red('ERROR:'),
-          'Found errors while running', colors.cyan(cmd));
-    }
-  },
-  runPresubmitTests: function() {
-    timedExecOrDie('gulp presubmit');
-  },
-  buildValidatorWebUI: function() {
-    timedExecOrDie('gulp validator-webui');
-  },
-  buildValidator: function() {
-    timedExecOrDie('gulp validator');
-  },
-  updatePackages: function() {
-    timedExecOrDie('gulp update-packages');
-  },
-};
-
-module.exports = {
-  command,
-};
diff --git a/build-system/pr-check/dist-test.js b/build-system/pr-check/dist-test.js
new file mode 100644
index 0000000000000..08c95e4b3afc9
--- /dev/null
+++ b/build-system/pr-check/dist-test.js
@@ -0,0 +1,72 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+/**
+ * @fileoverview
+ * This script runs the bundle size check and single pass test.
+ * This is run during the CI stage = test; job = dist tests.
+ */
+
+const {determineBuildTargets} = require('./build-target');
+const {isTravisPushBuild} = require('../travis');
+const {startTimer, stopTimer, timedExecOrDie, unzipBuildOutput} = require('./utils');
+
+const FILENAME = 'dist-test.js';
+
+function runSinglePassTest_() {
+  timedExecOrDie('rm -R dist');
+  timedExecOrDie('gulp dist --fortesting --single_pass --psuedonames');
+  timedExecOrDie('gulp test --integration' +
+   '--nobuild --compiled --single_pass');
+  timedExecOrDie('rm -R dist');
+}
+
+function main() {
+  const startTime = startTimer(FILENAME);
+  const buildTargets = determineBuildTargets();
+
+  if (isTravisPushBuild()) {
+    timedExecOrDie('gulp dist --fortesting --noextensions');
+    timedExecOrDie('gulp bundle-size --on-push-build');
+    runSinglePassTest_();
+  }
+  else {
+    let runTests = buildTargets.has('RUNTIME');
+
+    unzipBuildOutput(); //TODO(estherkim): does this belong here?
+    timedExecOrDie('gulp dist --fortesting --noextensions');
+    timedExecOrDie('gulp bundle-size ' +
+    `${buildTargets.has('RUNTIME') ? '--on_pr_build' : '--on_skipped_build'}`);
+
+    if (buildTargets.has('RUNTIME') ||
+    buildTargets.has('BUILD_SYSTEM') ||
+    buildTargets.has('INTEGRATION_TEST')) {
+      runSinglePassTest_();
+      runTests = true;
+    }
+
+    if (!runTests) {
+      console.log('Skipping dist tests because this commit does ' +
+      'not affect the runtime, build system, or integration test files.');
+    }
+  }
+
+  stopTimer(FILENAME, startTime);
+  return 0;
+}
+
+process.exit(main());
diff --git a/build-system/pr-check/local-test.js b/build-system/pr-check/local-test.js
new file mode 100644
index 0000000000000..28124c83a28cd
--- /dev/null
+++ b/build-system/pr-check/local-test.js
@@ -0,0 +1,82 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+/**
+ * @fileoverview
+ *This script runs the unit and integration tests on a local Travis VM.
+ * This is run during the CI stage = test; job = local tests.
+ */
+
+const {determineBuildTargets} = require('./build-target');
+const {isTravisPushBuild} = require('../travis');
+const {startTimer, stopTimer, timedExecOrDie, unzipBuildOutput} = require('./utils');
+
+const FILENAME = 'local-test.js';
+
+function main() {
+  const startTime = startTimer(FILENAME);
+  const buildTargets = determineBuildTargets();
+  unzipBuildOutput();
+  if (isTravisPushBuild()) {
+    timedExecOrDie('gulp test --integration --nobuild --coverage');
+    timedExecOrDie('gulp test --unit --nobuild --headless --coverage');
+    timedExecOrDie('gulp test --dev_dashboard --nobuild');
+    //TODO(estherkim): turn on when stabilized :)
+    //timedExecOrDie('gulp e2e --nobuild');
+  }
+  else {
+    let runTests = false;
+
+    if (buildTargets.has('RUNTIME') ||
+    buildTargets.has('BUILD_SYSTEM') ||
+    buildTargets.has('UNIT_TEST')) {
+      timedExecOrDie('gulp test --nobuild --headless --local-changes');
+      runTests = true;
+    }
+
+    if (buildTargets.has('RUNTIME') ||
+    buildTargets.has('BUILD_SYSTEM') ||
+    buildTargets.has('INTEGRATION_TEST')) {
+      timedExecOrDie('gulp test --integraton --nobuild --headless --coverage');
+      runTests = true;
+    }
+
+    if (buildTargets.has('RUNTIME') ||
+    buildTargets.has('BUILD_SYSTEM')) {
+      timedExecOrDie('gulp test --unit --nobuild --headless --coverage');
+      //TODO(estherkim): turn on when stabilized :)
+      //timedExecOrDie('gulp e2e --nobuild');
+      runTests = true;
+    }
+
+    if (buildTargets.has('DEV_DASHBOARD')) {
+      timedExecOrDie('gulp test --dev_dashboard --nobuild');
+      runTests = true;
+    }
+
+    if (!runTests) {
+      console.log('Skipping unit and integration tests because ' +
+      'this commit not affect the runtime, build system, ' +
+      'unit test files, integration test files, or the dev dashboard.');
+    }
+  }
+
+  stopTimer(FILENAME, startTime);
+  return 0;
+}
+
+process.exit(main());
diff --git a/build-system/pr-check/remote-test.js b/build-system/pr-check/remote-test.js
new file mode 100644
index 0000000000000..fe9f669fda88a
--- /dev/null
+++ b/build-system/pr-check/remote-test.js
@@ -0,0 +1,73 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+/**
+ * @fileoverview
+ * This script kicks off the unit and integration tests on Sauce Labs.
+ * This is run during the CI stage = test; job = remote tests.
+ */
+
+const {determineBuildTargets} = require('./build-target');
+const {isTravisPushBuild} = require('../travis');
+const {startTimer,
+  stopTimer,
+  startSauceConnect,
+  stopSauceConnect,
+  timedExecOrDie,
+  unzipBuildOutput} = require('./utils');
+
+const FILENAME = 'remote-test.js';
+
+function main() {
+  const startTime = startTimer(FILENAME);
+  const buildTargets = determineBuildTargets();
+  unzipBuildOutput();
+  startSauceConnect(FILENAME);
+
+  if (isTravisPushBuild()) {
+    timedExecOrDie('gulp test --unit --nobuild --saucelabs_lite');
+    timedExecOrDie('gulp test --integration --nobuild --compiled --saucelabs');
+  }
+  else {
+    let runTests = false;
+
+    if (buildTargets.has('RUNTIME') ||
+    buildTargets.has('BUILD_SYSTEM')) {
+      timedExecOrDie('gulp test --unit --nobuild --saucelabs_lite');
+      runTests = true;
+    }
+
+    if (buildTargets.has('RUNTIME') ||
+    buildTargets.has('BUILD_SYSTEM') ||
+    buildTargets.has('INTEGRATION_TEST')) {
+      timedExecOrDie('gulp test --integration --nobuild --saucelabs');
+      runTests = true;
+    }
+
+    if (!runTests) {
+      console.log('Skipping Sauce Labs unit and integration tests because ' +
+      'this commit not affect the runtime, build system, ' +
+      'or integration test files.');
+    }
+  }
+
+  stopSauceConnect(FILENAME);
+  stopTimer(FILENAME, startTime);
+  return 0;
+}
+
+process.exit(main());
diff --git a/build-system/pr-check/utils.js b/build-system/pr-check/utils.js
new file mode 100644
index 0000000000000..35aa7bd7b78ec
--- /dev/null
+++ b/build-system/pr-check/utils.js
@@ -0,0 +1,140 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+const colors = require('ansi-colors');
+const {execOrDie, exec, getStdout} = require('../exec');
+const {travisBuildNumber} = require('../travis');
+const BUILD_OUTPUT_FILE = `amp_build_${travisBuildNumber()}.zip`;
+const BUILD_OUTPUT_DIRS = 'build/ dist/ dist.3p/';
+const BUILD_OUTPUT_STORAGE_LOCATION = 'gs://amp-travis-builds';
+
+/**
+ * Starts connection to Sauce Labs after getting account credentials
+ * @param {string} functionName
+ */
+function startSauceConnect(functionName) {
+  process.env['SAUCE_USERNAME'] = 'amphtml';
+  process.env['SAUCE_ACCESS_KEY'] = getStdout('curl --silent ' +
+      'https://amphtml-sauce-token-dealer.appspot.com/getJwtToken').trim();
+  const startScCmd = 'build-system/sauce_connect/start_sauce_connect.sh';
+  const fileLogPrefix = colors.bold(colors.yellow(`${functionName}:`));
+  console.log('\n' + fileLogPrefix,
+      'Starting Sauce Connect Proxy:', colors.cyan(startScCmd));
+  execOrDie(startScCmd);
+}
+
+/**
+ * Stops connection to Sauce Labs
+ * @param {string} functionName
+ */
+function stopSauceConnect(functionName) {
+  const stopScCmd = 'build-system/sauce_connect/stop_sauce_connect.sh';
+  const fileLogPrefix = colors.bold(colors.yellow(`${functionName}:`));
+  console.log('\n' + fileLogPrefix,
+      'Stopping Sauce Connect Proxy:', colors.cyan(stopScCmd));
+  execOrDie(stopScCmd);
+}
+
+/**
+ * Starts a timer to measure the execution time of the given function.
+ * @param {string} functionName
+ * @return {DOMHighResTimeStamp}
+ */
+function startTimer(functionName) {
+  const startTime = Date.now();
+  const fileLogPrefix = colors.bold(colors.yellow(`${functionName}:`));
+  console.log(
+      '\n' + fileLogPrefix, 'Running', colors.cyan(functionName) + '...');
+  return startTime;
+}
+
+/**
+ * Stops the timer for the given function and prints the execution time.
+ * @param {string} functionName
+ * @param {DOMHighResTimeStamp} startTime
+ * @return {number}
+ */
+function stopTimer(functionName, startTime) {
+  const endTime = Date.now();
+  const executionTime = new Date(endTime - startTime);
+  const mins = executionTime.getMinutes();
+  const secs = executionTime.getSeconds();
+  const fileLogPrefix = colors.bold(colors.yellow(`${functionName}:`));
+  console.log(
+      fileLogPrefix, 'Done running', colors.cyan(functionName),
+      'Total time:', colors.green(mins + 'm ' + secs + 's'));
+}
+
+/**
+ * Executes the provided command and times it. Errors, if any, are printed.
+ * @param {string} cmd
+ * @return {<Object>} Process info.
+ */
+function timedExec(cmd) {
+  const startTime = startTimer(cmd);
+  const p = exec(cmd);
+  stopTimer(cmd, startTime);
+  return p;
+}
+
+/**
+ * Executes the provided command and times it. The program terminates in case of
+ * failure.
+ * @param {string} cmd
+ */
+function timedExecOrDie(cmd) {
+  const startTime = startTimer(cmd);
+  execOrDie(cmd);
+  stopTimer(cmd, startTime);
+}
+
+
+function unzipBuildOutput() {
+  timedExecOrDie('gsutil cp ' +
+      `${BUILD_OUTPUT_STORAGE_LOCATION}/${BUILD_OUTPUT_FILE} ` +
+      `${BUILD_OUTPUT_FILE}`);
+  timedExecOrDie(`ls ${BUILD_OUTPUT_FILE}`);
+  timedExecOrDie(
+      `log="$(unzip -o ${BUILD_OUTPUT_FILE})" && ` +
+      'echo travis_fold:start:unzip_results && echo ${log} && ' +
+      'echo travis_fold:end:unzip_results');
+  timedExecOrDie(
+      `log="$(ls -la ${BUILD_OUTPUT_DIRS})" && ` +
+      'echo travis_fold:start:verify_unzip_results && echo ${log} && ' +
+      'echo travis_fold:end:verify_unzip_results');
+}
+
+function zipBuildOutput() {
+  timedExecOrDie(
+      `log="$(zip -r ${BUILD_OUTPUT_FILE} ${BUILD_OUTPUT_DIRS})" && ` +
+      'echo travis_fold:start:zip_results && echo ${log} && ' +
+      'echo travis_fold:end:zip_results');
+  timedExecOrDie(`gsutil -m cp -r ${BUILD_OUTPUT_FILE} `
+    + `${BUILD_OUTPUT_STORAGE_LOCATION}`);
+}
+
+
+module.exports = {
+  startTimer,
+  stopTimer,
+  startSauceConnect,
+  stopSauceConnect,
+  timedExec,
+  timedExecOrDie,
+  unzipBuildOutput,
+  zipBuildOutput,
+};
diff --git a/build-system/pr-check/validator.js b/build-system/pr-check/validator.js
new file mode 100644
index 0000000000000..a6f8699c8121d
--- /dev/null
+++ b/build-system/pr-check/validator.js
@@ -0,0 +1,53 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+/**
+ * @fileoverview
+ * This script runs validator tests.
+ * This is run during the CI stage = build; job = validator.
+ */
+
+const {determineBuildTargets} = require('./build-target');
+const {isTravisPushBuild} = require('../travis');
+const {startTimer, stopTimer, timedExecOrDie} = require('./utils');
+
+const FILENAME = 'validator.js';
+
+function main() {
+  const startTime = startTimer(FILENAME);
+  const buildTargets = determineBuildTargets();
+
+  if (isTravisPushBuild()) {
+    timedExecOrDie('gulp validator');
+    timedExecOrDie('gulp validator-webui');
+  }
+  else if (buildTargets.has('VALIDATOR')) {
+    timedExecOrDie('gulp validator');
+  }
+  else if (buildTargets.has('VALIDATOR_WEBUI')) {
+    timedExecOrDie('gulp validator-webui');
+  }
+  else {
+    console.log('Skipping validator job because this commit does ' +
+    'not affect the validator or validator web UI.');
+  }
+
+  stopTimer(FILENAME, startTime);
+  return 0;
+}
+
+process.exit(main());
diff --git a/build-system/pr-check/visual-diff-test.js b/build-system/pr-check/visual-diff-test.js
new file mode 100644
index 0000000000000..6dc57ddea4f0b
--- /dev/null
+++ b/build-system/pr-check/visual-diff-test.js
@@ -0,0 +1,62 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+/**
+ * @fileoverview
+ * This script runs the visual diff tests.
+ * This is run during the CI stage = test; job = visual diff tests.
+ */
+
+const atob = require('atob');
+const {determineBuildTargets} = require('./build-target');
+const {isTravisPushBuild} = require('../travis');
+const {startTimer, stopTimer, timedExecOrDie, unzipBuildOutput} = require('./utils');
+
+const FILENAME = 'visual-diff-test.js';
+
+function main() {
+  const startTime = startTimer(FILENAME);
+  const buildTargets = determineBuildTargets();
+
+  if (isTravisPushBuild()) {
+    unzipBuildOutput();
+    process.env['PERCY_TOKEN'] = atob(process.env.PERCY_TOKEN_ENCODED);
+    timedExecOrDie('gulp visual-diff --nobuild --master');
+  }
+  else {
+    if (buildTargets.has('RUNTIME') ||
+    buildTargets.has('BUILD_SYSTEM') ||
+    buildTargets.has('INTEGRATION_TEST') ||
+    buildTargets.has('VISUAL_DIFF') ||
+    buildTargets.has('FLAG_CONFIG')) {
+      unzipBuildOutput();
+      process.env['PERCY_TOKEN'] = atob(process.env.PERCY_TOKEN_ENCODED);
+      timedExecOrDie('gulp visual-diff --nobuild');
+    }
+    else {
+      timedExecOrDie('gulp visual-diff --nobuild --empty');
+      console.log('Skipping visual diff tests because this commit does ' +
+      'not affect the runtime, build system, integration test files, ' +
+      'visual diff test files, or flag config files.');
+    }
+  }
+
+  stopTimer(FILENAME, startTime);
+  return 0;
+}
+
+process.exit(main());
diff --git a/build-system/tasks/presubmit-checks.js b/build-system/tasks/presubmit-checks.js
index 384a9a0e1fd6d..a467fa462ed85 100644
--- a/build-system/tasks/presubmit-checks.js
+++ b/build-system/tasks/presubmit-checks.js
@@ -104,6 +104,14 @@ const forbiddenTerms = {
       'build-system/app.js',
       'build-system/amp4test.js',
       'build-system/check-package-manager.js',
+      'build-system/pr-check/build.js',
+      'build-system/pr-check/checks.js',
+      'build-system/pr-check/dist-test.js',
+      'build-system/pr-check/local-test.js',
+      'build-system/pr-check/remote-test.js',
+      'build-system/pr-check/utils.js',
+      'build-system/pr-check/validator.js',
+      'build-system/pr-check/visual-diff-test.js',
       'validator/nodejs/index.js', // NodeJs only.
       'validator/engine/parse-css.js',
       'validator/engine/validator-in-browser.js',
diff --git a/build-system/travis.js b/build-system/travis.js
index 5519d6caacac5..b8d023338440e 100644
--- a/build-system/travis.js
+++ b/build-system/travis.js
@@ -50,6 +50,18 @@ exports.isTravisPushBuild = function() {
       process.env.TRAVIS_EVENT_TYPE === 'push';
 };
 
+/**
+ * Returns the build number of the ongoing Travis build.
+ * @return {string}
+ */
+exports.travisBuildNumber = function() {
+  if (!exports.isTravisBuild()) {
+    log(red('ERROR:'), 'This is not a Travis build. Cannot get',
+        cyan('process.env.TRAVIS_BUILD_NUMBER') + '.');
+  }
+  return process.env.TRAVIS_BUILD_NUMBER;
+};
+
 /**
  * Returns the job number of the ongoing Travis build.
  * @return {string}