diff --git a/.gitattributes b/.gitattributes
index 0925d33..1c2642c 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -2,5 +2,6 @@
 /.gitignore export-ignore
 /.travis.yml export-ignore
 /examples/ export-ignore
-/phpunit.xml.dist export-ignore
+/phpunit.xml export-ignore
+/phpunit-legacy.xml export-ignore
 /tests/ export-ignore
diff --git a/.travis.yml b/.travis.yml
index d0dc010..b905be4 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,7 @@ language: php
 # lock distro so new future defaults will not break the build
 dist: trusty
 
-matrix:
+jobs:
   include:
     - php: 5.3
       dist: precise
@@ -16,15 +16,12 @@ matrix:
     - php: 7.3
     - php: 7.4
     - php: hhvm-3.18
-      install:
-        - composer require phpunit/phpunit:^5 --dev --no-interaction # requires legacy phpunit
   allow_failures:
     - php: hhvm-3.18
 
-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-legacy.xml; fi
diff --git a/composer.json b/composer.json
index 877eb02..051be5f 100644
--- a/composer.json
+++ b/composer.json
@@ -25,6 +25,6 @@
     "require-dev": {
         "clue/buzz-react": "^2.4",
         "clue/ndjson-react": "^1.0",
-        "phpunit/phpunit": "^7.0 || ^6.4 || ^5.7 || ^4.8.35"
+        "phpunit/phpunit": "^9.3 || ^5.7 || ^4.8.35"
     }
 }
diff --git a/phpunit.xml.dist b/phpunit-legacy.xml
similarity index 51%
rename from phpunit.xml.dist
rename to phpunit-legacy.xml
index 59cfa84..6b429dd 100644
--- a/phpunit.xml.dist
+++ b/phpunit-legacy.xml
@@ -1,6 +1,10 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<phpunit bootstrap="vendor/autoload.php" colors="true">
+<!-- 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="Flux test suite">
             <directory>./tests/</directory>
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..fe1143b
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!-- 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="Flux test suite">
+            <directory>./tests/</directory>
+        </testsuite>
+    </testsuites>
+    <coverage>
+        <include>
+            <directory>./src/</directory>
+        </include>
+    </coverage>
+</phpunit>
diff --git a/tests/TestCase.php b/tests/TestCase.php
new file mode 100644
index 0000000..d595a51
--- /dev/null
+++ b/tests/TestCase.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace Clue\Tests\React\Flux;
+
+use PHPUnit\Framework\TestCase as BaseTestCase;
+
+class TestCase extends BaseTestCase
+{
+    protected function expectCallableOnce()
+    {
+        $mock = $this->createCallableMock();
+        $mock->expects($this->once())->method('__invoke');
+
+        return $mock;
+    }
+
+    protected function expectCallableOnceWith($param)
+    {
+        $mock = $this->createCallableMock();
+        $mock->expects($this->once()) ->method('__invoke')->with($param);
+
+        return $mock;
+    }
+
+    protected function expectCallableNever()
+    {
+        $mock = $this->createCallableMock();
+        $mock->expects($this->never())->method('__invoke');
+
+        return $mock;
+    }
+
+    protected function createCallableMock()
+    {
+        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 $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
+        }
+    }
+
+    public function setExpectedException($exception, $exceptionMessage = '', $exceptionCode = null)
+    {
+        if (method_exists($this, 'expectException')) {
+            // PHPUnit 6+
+            $this->expectException($exception);
+            if ($exceptionMessage !== '') {
+                $this->expectExceptionMessage($exceptionMessage);
+            }
+            if ($exceptionCode !== null) {
+                $this->expectExceptionCode($exceptionCode);
+            }
+        } else {
+            // legacy PHPUnit 4 - PHPUnit 5
+            parent::setExpectedException($exception, $exceptionMessage, $exceptionCode);
+        }
+    }
+}
diff --git a/tests/TransformerAllTest.php b/tests/TransformerAllTest.php
index c09a388..6bba8cc 100644
--- a/tests/TransformerAllTest.php
+++ b/tests/TransformerAllTest.php
@@ -3,7 +3,6 @@
 namespace Clue\Tests\React\Flux;
 
 use Clue\React\Flux\Transformer;
-use PHPUnit\Framework\TestCase;
 use React\Promise\Deferred;
 use React\Promise\Promise;
 use React\Stream\ThroughStream;
@@ -203,42 +202,4 @@ public function testPendingOperationWillBeCancelledIfOneOperationRejects()
 
         $promise->then(null, $this->expectCallableOnce());
     }
-
-    protected function expectCallableOnce()
-    {
-        $mock = $this->createCallableMock();
-
-        $mock
-            ->expects($this->once())
-            ->method('__invoke');
-
-        return $mock;
-    }
-
-    protected function expectCallableOnceWith($param)
-    {
-        $mock = $this->createCallableMock();
-
-        $mock
-            ->expects($this->once())
-            ->method('__invoke')
-            ->with($param);
-
-        return $mock;
-    }
-
-    protected function expectCallableNever()
-    {
-        $mock = $this->createCallableMock();
-        $mock
-            ->expects($this->never())
-            ->method('__invoke');
-
-        return $mock;
-    }
-
-    protected function createCallableMock()
-    {
-        return $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
-    }
 }
diff --git a/tests/TransformerAnyTest.php b/tests/TransformerAnyTest.php
index 0ef5483..2a95f1d 100644
--- a/tests/TransformerAnyTest.php
+++ b/tests/TransformerAnyTest.php
@@ -3,7 +3,6 @@
 namespace Clue\Tests\React\Flux;
 
 use Clue\React\Flux\Transformer;
-use PHPUnit\Framework\TestCase;
 use React\Promise\Deferred;
 use React\Promise\Promise;
 use React\Stream\ThroughStream;
@@ -211,42 +210,4 @@ public function testPendingOperationWillBeCancelledIfOneOperationResolves()
 
         $promise->then($this->expectCallableOnceWith('hello'));
     }
-
-    protected function expectCallableOnce()
-    {
-        $mock = $this->createCallableMock();
-
-        $mock
-            ->expects($this->once())
-            ->method('__invoke');
-
-        return $mock;
-    }
-
-    protected function expectCallableOnceWith($param)
-    {
-        $mock = $this->createCallableMock();
-
-        $mock
-            ->expects($this->once())
-            ->method('__invoke')
-            ->with($param);
-
-        return $mock;
-    }
-
-    protected function expectCallableNever()
-    {
-        $mock = $this->createCallableMock();
-        $mock
-            ->expects($this->never())
-            ->method('__invoke');
-
-        return $mock;
-    }
-
-    protected function createCallableMock()
-    {
-        return $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
-    }
 }
diff --git a/tests/TransformerTest.php b/tests/TransformerTest.php
index 8bf8272..50a6836 100644
--- a/tests/TransformerTest.php
+++ b/tests/TransformerTest.php
@@ -3,25 +3,20 @@
 namespace Clue\Tests\React\Flux;
 
 use Clue\React\Flux\Transformer;
-use PHPUnit\Framework\TestCase;
 use React\Promise;
 use React\Promise\Deferred;
 
 class TransformerTest extends TestCase
 {
-    /**
-     * @expectedException InvalidArgumentException
-     */
     public function testConstructorThrowsIfConcurrencyIsBelowOne()
     {
+        $this->setExpectedException('InvalidArgumentException');
         new Transformer(0, function () { });
     }
 
-    /**
-     * @expectedException InvalidArgumentException
-     */
     public function testConstructorThrowsIfHandlerIsNotCallable()
     {
+        $this->setExpectedException('InvalidArgumentException');
         new Transformer(1, 'foo');
     }
 
@@ -404,42 +399,4 @@ public function testPipeReturnsDestinationStream()
 
         $this->assertSame($ret, $dest);
     }
-
-    protected function expectCallableOnce()
-    {
-        $mock = $this->createCallableMock();
-
-        $mock
-            ->expects($this->once())
-            ->method('__invoke');
-
-        return $mock;
-    }
-
-    protected function expectCallableOnceWith($param)
-    {
-        $mock = $this->createCallableMock();
-
-        $mock
-            ->expects($this->once())
-            ->method('__invoke')
-            ->with($param);
-
-        return $mock;
-    }
-
-    protected function expectCallableNever()
-    {
-        $mock = $this->createCallableMock();
-        $mock
-            ->expects($this->never())
-            ->method('__invoke');
-
-        return $mock;
-    }
-
-    protected function createCallableMock()
-    {
-        return $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
-    }
 }