diff --git a/.github/workflows/code-quality.yml b/.github/workflows/code-quality.yml
new file mode 100644
index 000000000..85c844d05
--- /dev/null
+++ b/.github/workflows/code-quality.yml
@@ -0,0 +1,74 @@
+name: Code Quality Checks
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+
+  lint: #-----------------------------------------------------------------------
+    name: Lint PHP files
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out source code
+        uses: actions/checkout@v2
+
+      - name: Set up PHP envirnoment
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '7.4'
+          tools: cs2pr
+
+      - name: Get Composer cache Directory
+        id: composer-cache
+        run: |
+          echo "::set-output name=dir::$(composer config cache-files-dir)"
+
+      - name: Use Composer cache
+        uses: actions/cache@v1
+        with:
+          path: ${{ steps['composer-cache'].outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-progress --no-suggest
+
+      - name: Run Linter
+        run: vendor/bin/parallel-lint -j 10 . --exclude vendor --checkstyle | cs2pr
+
+  phpcs: #----------------------------------------------------------------------
+    name: PHPCS
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out source code
+        uses: actions/checkout@v2
+
+      - name: Set up PHP envirnoment
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '7.4'
+          tools: cs2pr
+
+      - name: Get Composer cache Directory
+        id: composer-cache
+        run: |
+          echo "::set-output name=dir::$(composer config cache-files-dir)"
+
+      - name: Use Composer cache
+        uses: actions/cache@v1
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-progress --no-suggest
+
+      - name: Run PHPCS
+        run: vendor/bin/phpcs -q --report=checkstyle | cs2pr
diff --git a/.github/workflows/testing.yml b/.github/workflows/testing.yml
new file mode 100644
index 000000000..53b86ff26
--- /dev/null
+++ b/.github/workflows/testing.yml
@@ -0,0 +1,96 @@
+name: Testing
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+
+  unit:
+    name: Unit test /  PHP ${{ matrix.php }}
+    strategy:
+      fail-fast: false
+      matrix:
+        php: ['5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0']
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out source code
+        uses: actions/checkout@v2
+
+      - name: Set up PHP environment
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '${{ matrix.php }}'
+          coverage: none
+          tools: composer,cs2pr
+
+      - name: Get Composer cache Directory
+        id: composer-cache
+        run: |
+          echo "::set-output name=dir::$(composer config cache-files-dir)"
+
+      - name: Use Composer cache
+        uses: actions/cache@master
+        with:
+          path: ${{ steps['composer-cache'].outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-progress --no-suggest
+
+      - name: Setup problem matcher to provide annotations for PHPUnit
+        run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
+
+      - name: Setup Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: '3.8'
+
+      - name: Setup proxy server
+        run: pip3 install mitmproxy
+
+      - name: Start test server
+        run: |
+          PORT=8080 vendor/bin/start.sh
+          echo "REQUESTS_TEST_HOST_HTTP=localhost:8080" >> $GITHUB_ENV
+
+      - name: Start proxy server
+        run: |
+          PORT=9002 tests/utils/proxy/start.sh
+          PORT=9003 AUTH="test:pass" tests/utils/proxy/start.sh
+          echo "REQUESTS_HTTP_PROXY=localhost:9002" >> $GITHUB_ENV
+          echo "REQUESTS_HTTP_PROXY=localhost:9002" >> $GITHUB_ENV
+          echo "REQUESTS_HTTP_PROXY_AUTH=localhost:9003" >> $GITHUB_ENV
+          echo "REQUESTS_HTTP_PROXY_AUTH_USER=test" >> $GITHUB_ENV
+          echo "REQUESTS_HTTP_PROXY_AUTH_PASS=pass" >> $GITHUB_ENV
+
+      - name: Ensure the HTTPS test instance on Heroku is spun up
+        run: curl -s -I http://requests-php-tests.herokuapp.com/ > /dev/null
+
+      - name: Check mitmproxy version
+        run: mitmdump --version
+
+      - name: Ping localhost domain
+        run: ping -c1 localhost
+
+      - name: Access localhost on port 8080
+        run: curl -i http://localhost:8080
+
+      - name: Access localhost on port 9002
+        run: curl -i http://localhost:9002
+
+      - name: Run PHPUnit
+        run: composer test
+
+      - name: Stop proxy server
+        run: |
+          PORT=9002 tests/utils/proxy/stop.sh
+          PORT=9003 tests/utils/proxy/stop.sh
+
+      - name: Stop test server
+        run: vendor/bin/stop.sh
diff --git a/.phpcs.xml.dist b/.phpcs.xml.dist
index 8381fb896..4e95aa118 100644
--- a/.phpcs.xml.dist
+++ b/.phpcs.xml.dist
@@ -40,11 +40,8 @@
 	#############################################################################
 	-->
 
-	<config name="testVersion" value="5.2-"/>
-	<rule ref="PHPCompatibility">
-		<!-- The example code may contain code samples targetted at PHP > 5.2. -->
-		<exclude-pattern>/examples/*\.php$</exclude-pattern>
-	</rule>
+	<config name="testVersion" value="5.5-"/>
+	<rule ref="PHPCompatibility"></rule>
 
 
 	<!--
diff --git a/composer.json b/composer.json
index 6d78734fe..5107e5a55 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,8 @@
 		"phpcompatibility/php-compatibility": "^9.0",
 		"wp-coding-standards/wpcs": "^2.0",
 		"dealerdirect/phpcodesniffer-composer-installer": "^0.7",
-		"yoast/phpunit-polyfills": "^0.2.0"
+		"yoast/phpunit-polyfills": "^0.2.0",
+		"php-parallel-lint/php-parallel-lint": "^1.2"
 	},
 	"type": "library",
 	"autoload": {
diff --git a/tests/Proxy/HTTP.php b/tests/Proxy/HTTP.php
index a06b1a682..45e290b5c 100644
--- a/tests/Proxy/HTTP.php
+++ b/tests/Proxy/HTTP.php
@@ -118,7 +118,7 @@ public function testConnectWithAuth($transport) {
 	public function testConnectWithInvalidAuth($transport) {
 		$this->checkProxyAvailable('auth');
 
-		$options  = array(
+		$options = array(
 			'proxy'     => array(
 				REQUESTS_HTTP_PROXY_AUTH,
 				REQUESTS_HTTP_PROXY_AUTH_USER . '!',
@@ -126,6 +126,13 @@ public function testConnectWithInvalidAuth($transport) {
 			),
 			'transport' => $transport,
 		);
+
+		if ($transport === 'Requests_Transport_fsockopen') {
+			// @TODO fsockopen connection times out on invalid auth instead of returning 407.
+			$this->expectException('Requests_Exception');
+			$this->expectExceptionMessage('fsocket timed out');
+		}
+
 		$response = Requests::get(httpbin('/get'), array(), $options);
 		$this->assertSame(407, $response->status_code);
 	}
diff --git a/tests/TestCase.php b/tests/TestCase.php
new file mode 100644
index 000000000..c005b9928
--- /dev/null
+++ b/tests/TestCase.php
@@ -0,0 +1,5 @@
+<?php
+
+class RequestsTest_TestCase extends \Yoast\PHPUnitPolyfills\TestCases\TestCase {
+
+}
diff --git a/tests/utils/proxy/start.sh b/tests/utils/proxy/start.sh
index 4e7edeca6..14ac2fdd8 100755
--- a/tests/utils/proxy/start.sh
+++ b/tests/utils/proxy/start.sh
@@ -1,11 +1,19 @@
+#!/usr/bin/env bash
+
 PROXYDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 PORT=${PORT:-9000}
 
 PROXYBIN=${PROXYBIN:-"$(which mitmdump)"}
 ARGS="-s '$PROXYDIR/proxy.py' -p $PORT"
 if [[ ! -z "$AUTH" ]]; then
-	ARGS="$ARGS --singleuser=$AUTH"
+	ARGS="$ARGS --proxyauth $AUTH"
 fi
-PIDFILE="$PROXYDIR/proxy.pid"
+PIDFILE="$PROXYDIR/proxy-$PORT.pid"
+
+set -x
+
+start-stop-daemon --verbose --start --background --pidfile $PIDFILE --make-pidfile --exec $PROXYBIN -- $ARGS
 
-start-stop-daemon --start --background --pidfile $PIDFILE --make-pidfile --exec $PROXYBIN -- $ARGS
+ps -p $(cat $PIDFILE) -u
+sleep 2
+ps -p $(cat $PIDFILE) -u
diff --git a/tests/utils/proxy/stop.sh b/tests/utils/proxy/stop.sh
index 9854d04f5..8cb0eb92f 100755
--- a/tests/utils/proxy/stop.sh
+++ b/tests/utils/proxy/stop.sh
@@ -1,5 +1,10 @@
+#!/usr/bin/env bash
+
 PROXYDIR="$PWD/$(dirname $0)"
+PORT=${PORT:-9000}
+
+PIDFILE="$PROXYDIR/proxy-$PORT.pid"
 
-PIDFILE="$PROXYDIR/proxy.pid"
+set -x
 
-start-stop-daemon --stop --pidfile $PIDFILE --make-pidfile && rm $PROXYDIR/proxy.pid
+start-stop-daemon --verbose --stop --pidfile $PIDFILE --remove-pidfile