diff --git a/.travis.yml b/.travis.yml
index e880f6d636..9b6b1fac25 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,8 @@ cache:
   apt: true
   directories:
     - node_modules
+    - vendor
+    - $HOME/.composer/cache
 env:
   global:
     - WP_TRAVISCI=travis:phpunit
@@ -21,19 +23,8 @@ matrix:
   - php: 5.4
   - php: 5.3
   - php: 5.2
-  - php: hhvm
-    sudo: required
-    dist: trusty
-    group: edge
-    addons:
-      apt:
-        packages:
-        - mysql-server-5.6
-        - mysql-client-core-5.6
-        - mysql-client-5.6
   - php: nightly
   allow_failures:
-  - php: hhvm
   - php: nightly
 before_install:
 - |
@@ -52,7 +43,7 @@ before_install:
   fi
 before_script:
 - |
-  # Remove Xdebug for a huge performance increase, but not from nightly or hhvm:
+  # Remove Xdebug for a huge performance increase, but not from nightly:
   stable='^[0-9\.]+$'
   if [[ "$TRAVIS_PHP_VERSION" =~ $stable ]]; then
     phpenv config-rm xdebug.ini
@@ -67,9 +58,9 @@ before_script:
   # Install the specified version of PHPUnit depending on the PHP version:
   if [[ "$WP_TRAVISCI" == "travis:phpunit" ]]; then
     case "$TRAVIS_PHP_VERSION" in
-      7.1|7.0|hhvm|nightly)
-        echo "Using PHPUnit 5.7"
-        composer global require "phpunit/phpunit=5.7.*"
+      7.1|7.0|nightly)
+        echo "Using PHPUnit 6.1"
+        composer global require "phpunit/phpunit=6.1.*"
         ;;
       5.6|5.5|5.4|5.3)
         echo "Using PHPUnit 4.8"
@@ -94,11 +85,7 @@ before_script:
 - mysql --version
 - phpenv versions
 - php --version
-- |
-  # Debug PHP extensions, but not on HHVM because the command hangs indefinitely:
-  if [[ "$TRAVIS_PHP_VERSION" != 'hhvm' ]]; then
-    php -m
-  fi
+- php -m
 - npm --version
 - node --version
 - which phpunit
diff --git a/tests/phpunit/includes/bootstrap.php b/tests/phpunit/includes/bootstrap.php
index b462e7039b..1450736fd1 100644
--- a/tests/phpunit/includes/bootstrap.php
+++ b/tests/phpunit/includes/bootstrap.php
@@ -3,6 +3,12 @@
  * Installs WordPress for running the tests and loads WordPress and the test libraries
  */
 
+/**
+ * Compatibility with PHPUnit 6+
+ */
+if ( class_exists( 'PHPUnit\Runner\Version' ) ) {
+	require_once dirname( __FILE__ ) . '/phpunit6-compat.php';
+}
 
 $config_file_path = dirname( dirname( __FILE__ ) );
 if ( ! file_exists( $config_file_path . '/wp-tests-config.php' ) ) {
diff --git a/tests/phpunit/includes/phpunit6-compat.php b/tests/phpunit/includes/phpunit6-compat.php
new file mode 100644
index 0000000000..a5b0a9f5a8
--- /dev/null
+++ b/tests/phpunit/includes/phpunit6-compat.php
@@ -0,0 +1,37 @@
+<?php
+
+if ( class_exists( 'PHPUnit\Runner\Version' ) && version_compare( PHPUnit\Runner\Version::id(), '6.0', '>=' ) ) {
+
+	class_alias( 'PHPUnit\Framework\TestCase',                   'PHPUnit_Framework_TestCase' );
+	class_alias( 'PHPUnit\Framework\Exception',                  'PHPUnit_Framework_Exception' );
+	class_alias( 'PHPUnit\Framework\ExpectationFailedException', 'PHPUnit_Framework_ExpectationFailedException' );
+	class_alias( 'PHPUnit\Framework\Error\Notice',               'PHPUnit_Framework_Error_Notice' );
+	class_alias( 'PHPUnit\Framework\Test',                       'PHPUnit_Framework_Test' );
+	class_alias( 'PHPUnit\Framework\Warning',                    'PHPUnit_Framework_Warning' );
+	class_alias( 'PHPUnit\Framework\AssertionFailedError',       'PHPUnit_Framework_AssertionFailedError' );
+	class_alias( 'PHPUnit\Framework\TestSuite',                  'PHPUnit_Framework_TestSuite' );
+	class_alias( 'PHPUnit\Framework\TestListener',               'PHPUnit_Framework_TestListener' );
+	class_alias( 'PHPUnit\Util\GlobalState',                     'PHPUnit_Util_GlobalState' );
+	class_alias( 'PHPUnit\Util\Getopt',                          'PHPUnit_Util_Getopt' );
+
+	class PHPUnit_Util_Test extends PHPUnit\Util\Test {
+
+		public static function getTickets( $className, $methodName ) {
+			$annotations = self::parseTestMethodAnnotations( $className, $methodName );
+
+			$tickets = array();
+
+			if ( isset( $annotations['class']['ticket'] ) ) {
+				$tickets = $annotations['class']['ticket'];
+			}
+
+			if ( isset( $annotations['method']['ticket'] ) ) {
+				$tickets = array_merge( $tickets, $annotations['method']['ticket'] );
+			}
+
+			return array_unique( $tickets );
+		}
+
+	}
+
+}
diff --git a/tests/phpunit/includes/testcase-ajax.php b/tests/phpunit/includes/testcase-ajax.php
index 787e6bf5fd..19a87b2a74 100644
--- a/tests/phpunit/includes/testcase-ajax.php
+++ b/tests/phpunit/includes/testcase-ajax.php
@@ -200,4 +200,25 @@ abstract class WP_Ajax_UnitTestCase extends WP_UnitTestCase {
 		if ( !empty( $buffer ) )
 			$this->_last_response = $buffer;
 	}
+
+	/**
+	 * PHPUnit 6+ compatibility shim.
+	 *
+	 * @param mixed      $exception
+	 * @param string     $message
+	 * @param int|string $code
+	 */
+	public function setExpectedException( $exception, $message = '', $code = null ) {
+		if ( is_callable( 'parent::setExpectedException' ) ) {
+			parent::setExpectedException( $exception, $message, $code );
+		} else {
+			$this->expectException( $exception );
+			if ( '' !== $message ) {
+				$this->expectExceptionMessage( $message );
+			}
+			if ( null !== $code ) {
+				$this->expectExceptionCode( $code );
+			}
+		}
+	}
 }