diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a33e503860e122d1a2e58cb4e8a21742bd03af11..6c1c666dcdf80d965ae2b65d25b19c328e8f3b4f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -3,6 +3,10 @@ variables:
   MYSQL_DATABASE: wordpress_tests
   MYSQL_ROOT_PASSWORD: mysql
 
+cache:
+  paths:
+    - $HOME/.composer
+
 before_script:
   # Install dependencies
 
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 4e5b3cc05118e55f846186a2136b7dab1d94a65f..ce4684590410004d383ac4c99a0bfa098387b94d 100755
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -5,27 +5,27 @@
  * @package Camo_Image_Proxy
  */
 
-$_tests_dir = getenv( 'WP_TESTS_DIR' );
+$camo_tests_dir = getenv( 'WP_TESTS_DIR' );
 
-if ( ! $_tests_dir ) {
-	$_tests_dir = rtrim( sys_get_temp_dir(), '/\\' ) . '/wordpress-tests-lib';
+if ( ! $camo_tests_dir ) {
+	$camo_tests_dir = rtrim( sys_get_temp_dir(), '/\\' ) . '/wordpress-tests-lib';
 }
 
-if ( ! file_exists( $_tests_dir . '/includes/functions.php' ) ) {
-	echo "Could not find $_tests_dir/includes/functions.php, have you run bin/install-wp-tests.sh ?" . PHP_EOL;
+if ( ! file_exists( $camo_tests_dir . '/includes/functions.php' ) ) {
+	echo "Could not find $camo_tests_dir/includes/functions.php, have you run bin/install-wp-tests.sh ?" . PHP_EOL; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
 	exit( 1 );
 }
 
 // Give access to tests_add_filter() function.
-require_once $_tests_dir . '/includes/functions.php';
+require_once $camo_tests_dir . '/includes/functions.php';
 
 /**
  * Manually load the plugin being tested.
  */
-function _manually_load_plugin() {
+function camo_manually_load_plugin() {
 	require dirname( dirname( __FILE__ ) ) . '/camo-image-proxy.php';
 }
-tests_add_filter( 'muplugins_loaded', '_manually_load_plugin' );
+tests_add_filter( 'muplugins_loaded', 'camo_manually_load_plugin' );
 
 // Start up the WP testing environment.
-require $_tests_dir . '/includes/bootstrap.php';
+require $camo_tests_dir . '/includes/bootstrap.php';
diff --git a/tests/test-sample.php b/tests/test-sample.php
index f4e62d1791e546d84193345b8003ff3186c9fdb3..9d79786fb8cd3b3224f4828bcaca0f6a52ba23bd 100755
--- a/tests/test-sample.php
+++ b/tests/test-sample.php
@@ -13,7 +13,7 @@ class SampleTest extends WP_UnitTestCase {
 	/**
 	 * A single example test.
 	 */
-	function test_sample() {
+	public function test_sample() {
 		// Replace this with some actual testing code.
 		$this->assertTrue( true );
 	}