diff --git a/.gitattributes b/.gitattributes
index 0925d33..eccc763 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -3,4 +3,5 @@
 /.travis.yml export-ignore
 /examples/ export-ignore
 /phpunit.xml.dist export-ignore
+/phpunit.xml.legacy export-ignore
 /tests/ export-ignore
diff --git a/.travis.yml b/.travis.yml
index 845ce05..9511e94 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,7 @@ language: php
 # lock distro so future defaults will not break the build
 dist: trusty
 
-matrix:
+jobs:
   include:
     - php: 5.3
       dist: precise
@@ -16,10 +16,9 @@ matrix:
     - php: 7.3
     - php: 7.4
 
-sudo: false
-
 install:
-  - composer install --no-interaction
+  - composer install
 
 script:
-  - vendor/bin/phpunit --coverage-text
+  - if [[ "$TRAVIS_PHP_VERSION" > "7.2" ]]; then vendor/bin/phpunit --coverage-text; fi
+  - if [[ "$TRAVIS_PHP_VERSION" < "7.3" ]]; then vendor/bin/phpunit --coverage-text -c phpunit.xml.legacy; fi
diff --git a/composer.json b/composer.json
index a5cbbb0..dff6470 100644
--- a/composer.json
+++ b/composer.json
@@ -24,6 +24,6 @@
         "react/promise": "^2.0 || ^1.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.0 || ^6.0 || ^5.0 || ^4.8.35"
+        "phpunit/phpunit": "^9.3 || ^5.7 || ^4.8.35"
     }
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 471539b..8ef3e91 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,14 +1,19 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<phpunit bootstrap="vendor/autoload.php" colors="true">
+<!-- PHPUnit configuration file with new format for PHPUnit 9.3+ -->
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+         cacheResult="false">
     <testsuites>
         <testsuite name="Shell React Test Suite">
             <directory>./tests/</directory>
         </testsuite>
     </testsuites>
-    <filter>
-        <whitelist>
+    <coverage>
+        <include>
             <directory>./src/</directory>
-        </whitelist>
-    </filter>
-</phpunit>
\ No newline at end of file
+        </include>
+    </coverage>
+</phpunit>
diff --git a/phpunit.xml.legacy b/phpunit.xml.legacy
new file mode 100644
index 0000000..dc15861
--- /dev/null
+++ b/phpunit.xml.legacy
@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!-- PHPUnit configuration file with old format for PHPUnit 9.2 or older -->
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/4.8/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true">
+    <testsuites>
+        <testsuite name="Shell React Test Suite">
+            <directory>./tests/</directory>
+        </testsuite>
+    </testsuites>
+    <filter>
+        <whitelist>
+            <directory>./src/</directory>
+        </whitelist>
+    </filter>
+</phpunit>
diff --git a/tests/DeferredShellTest.php b/tests/DeferredShellTest.php
index 2dabfb7..5825b33 100644
--- a/tests/DeferredShellTest.php
+++ b/tests/DeferredShellTest.php
@@ -8,7 +8,10 @@ class DeferredShellTest extends TestCase
 {
     private $stream;
 
-    public function setUp()
+    /**
+     * @before
+     */
+    public function setUpStream()
     {
         $this->stream = $this->getMockBuilder('React\Stream\DuplexStreamInterface')->getMock();
     }
diff --git a/tests/FunctionalTest.php b/tests/FunctionalTest.php
index 456724d..1434549 100644
--- a/tests/FunctionalTest.php
+++ b/tests/FunctionalTest.php
@@ -10,7 +10,10 @@ class FunctionalTest extends TestCase
     private $loop;
     private $launcher;
 
-    public function setUp()
+    /**
+     * @before
+     */
+    public function setUpLauncher()
     {
         $this->loop = Factory::create();
         $this->launcher = new ProcessLauncher($this->loop);
diff --git a/tests/ProcessLauncherTest.php b/tests/ProcessLauncherTest.php
index 884e03d..3e4a68a 100644
--- a/tests/ProcessLauncherTest.php
+++ b/tests/ProcessLauncherTest.php
@@ -9,7 +9,10 @@ class ProcessLauncherTest extends TestCase
     private $loop;
     private $processLauncher;
 
-    public function setUp()
+    /**
+     * @before
+     */
+    public function setUpProcessLauncher()
     {
         $this->loop = $this->getMockBuilder('React\EventLoop\LoopInterface')->getMock();
         $this->processLauncher = new ProcessLauncher($this->loop);
diff --git a/tests/TestCase.php b/tests/TestCase.php
index b6fe2bd..052104a 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -54,7 +54,13 @@ protected function expectCallableOnceParameter($type)
 
     protected function createCallableMock()
     {
-        return $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
+        if (method_exists('PHPUnit\Framework\MockObject\MockBuilder', 'addMethods')) {
+            // PHPUnit 9+
+            return $this->getMockBuilder('stdClass')->addMethods(array('__invoke'))->getMock();
+        } else {
+            // legacy PHPUnit 4 - PHPUnit 8
+            return $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
+        }
     }
 
     protected function expectPromiseResolve($promise)