diff --git a/composer.json b/composer.json
index aa590bd..06333f4 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,7 @@
         "react/promise": "^3 || ^2.7"
     },
     "require-dev": {
-        "phpstan/phpstan": "1.8.10 || 1.4.10",
+        "phpstan/phpstan": "1.9.2 || 1.4.10",
         "phpunit/phpunit": "^9.5 || ^7.5",
         "psr/container": "^2 || ^1"
     },
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 6112643..c4587eb 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -13,5 +13,3 @@ parameters:
         # ignore unknown `Fiber` class (PHP 8.1+)
         - '/^Instantiated class Fiber not found\.$/'
         - '/^Call to method (start|isTerminated|getReturn)\(\) on an unknown class Fiber\.$/'
-        # ignore incomplete type information for mocks in legacy PHPUnit 7.5
-        - '/^Parameter #\d+ .+ of .+ expects .+, PHPUnit\\Framework\\MockObject\\MockObject given\.$/'
diff --git a/tests/AppTest.php b/tests/AppTest.php
index 9433d03..7a2218e 100644
--- a/tests/AppTest.php
+++ b/tests/AppTest.php
@@ -74,6 +74,7 @@ public function testConstructWithContainerAssignsDefaultHandlersAndContainerForR
         $container->expects($this->once())->method('getAccessLogHandler')->willReturn($accessLogHandler);
         $container->expects($this->once())->method('getErrorHandler')->willReturn($errorHandler);
 
+        assert($container instanceof Container);
         $app = new App($container);
 
         $ref = new ReflectionProperty($app, 'handler');
@@ -109,6 +110,7 @@ public function testConstructWithContainerAndMiddlewareClassNameAssignsCallableF
         $container = $this->createMock(Container::class);
         $container->expects($this->once())->method('callable')->with('stdClass')->willReturn($middleware);
 
+        assert($container instanceof Container);
         $app = new App($container, \stdClass::class);
 
         $ref = new ReflectionProperty($app, 'handler');
@@ -224,6 +226,7 @@ public function testConstructWithContainerAndErrorHandlerClassAssignsErrorHandle
         $container = $this->createMock(Container::class);
         $container->expects($this->once())->method('getErrorHandler')->willReturn($errorHandler);
 
+        assert($container instanceof Container);
         $app = new App($container, ErrorHandler::class);
 
         $ref = new ReflectionProperty($app, 'handler');
@@ -257,6 +260,8 @@ public function testConstructWithMultipleContainersAndErrorHandlerClassAssignsEr
         $container = $this->createMock(Container::class);
         $container->expects($this->once())->method('getErrorHandler')->willReturn($errorHandler);
 
+        assert($unused instanceof Container);
+        assert($container instanceof Container);
         $app = new App($unused, $container, ErrorHandler::class, $unused);
 
         $ref = new ReflectionProperty($app, 'handler');
@@ -291,6 +296,8 @@ public function testConstructWithMultipleContainersAndMiddlewareAssignsErrorHand
         $container = $this->createMock(Container::class);
         $container->expects($this->once())->method('getErrorHandler')->willReturn($errorHandler);
 
+        assert($unused instanceof Container);
+        assert($container instanceof Container);
         $app = new App($unused, $container, $middleware, $unused);
 
         $ref = new ReflectionProperty($app, 'handler');
@@ -361,6 +368,9 @@ public function testConstructWithMultipleContainersAndMiddlewareAndErrorHandlerC
         $container2 = $this->createMock(Container::class);
         $container2->expects($this->once())->method('getErrorHandler')->willReturn($errorHandler2);
 
+        assert($unused instanceof Container);
+        assert($container1 instanceof Container);
+        assert($container2 instanceof Container);
         $app = new App($unused, $container1, $middleware, $container2, ErrorHandler::class, $unused);
 
         $ref = new ReflectionProperty($app, 'handler');
@@ -448,6 +458,7 @@ public function testConstructWithContainerAndAccessLogHandlerClassAndErrorHandle
         $container->expects($this->once())->method('getAccessLogHandler')->willReturn($accessLogHandler);
         $container->expects($this->once())->method('getErrorHandler')->willReturn($errorHandler);
 
+        assert($container instanceof Container);
         $app = new App($container, AccessLogHandler::class, ErrorHandler::class);
 
         $ref = new ReflectionProperty($app, 'handler');
@@ -515,6 +526,8 @@ public function testConstructWithMultipleContainersAndAccessLogHandlerClassAndEr
         $container->expects($this->once())->method('getAccessLogHandler')->willReturn($accessLogHandler);
         $container->expects($this->once())->method('getErrorHandler')->willReturn($errorHandler);
 
+        assert($unused instanceof Container);
+        assert($container instanceof Container);
         $app = new App($unused, $container, AccessLogHandler::class, ErrorHandler::class, $unused);
 
         $ref = new ReflectionProperty($app, 'handler');
@@ -554,6 +567,8 @@ public function testConstructWithMultipleContainersAndMiddlewareAssignsDefaultHa
         $container->expects($this->once())->method('getAccessLogHandler')->willReturn($accessLogHandler);
         $container->expects($this->once())->method('getErrorHandler')->willReturn($errorHandler);
 
+        assert($unused instanceof Container);
+        assert($container instanceof Container);
         $app = new App($unused, $container, $middleware, $unused);
 
         $ref = new ReflectionProperty($app, 'handler');
diff --git a/tests/ContainerTest.php b/tests/ContainerTest.php
index d33d722..26423a4 100644
--- a/tests/ContainerTest.php
+++ b/tests/ContainerTest.php
@@ -1982,6 +1982,7 @@ public function __invoke(ServerRequestInterface $request): Response
         $psr->expects($this->never())->method('has');
         $psr->expects($this->once())->method('get')->with(get_class($controller))->willReturn($controller);
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $callable = $container->callable(get_class($controller));
@@ -2002,6 +2003,7 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReturnsInvalidCl
         $psr->expects($this->never())->method('has');
         $psr->expects($this->once())->method('get')->with('FooBar')->willThrowException($exception);
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $callable = $container->callable('FooBar'); // @phpstan-ignore-line
@@ -2054,6 +2056,7 @@ public function testGetEnvReturnsStringFromPsrContainer(): void
         $psr->expects($this->once())->method('has')->with('X_FOO')->willReturn(true);
         $psr->expects($this->once())->method('get')->with('X_FOO')->willReturn('bar');
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $this->assertEquals('bar', $container->getEnv('X_FOO'));
@@ -2065,6 +2068,7 @@ public function testGetEnvReturnsNullIfPsrContainerHasNoEntry(): void
         $psr->expects($this->once())->method('has')->with('X_FOO')->willReturn(false);
         $psr->expects($this->never())->method('get');
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $this->assertNull($container->getEnv('X_FOO'));
@@ -2076,6 +2080,7 @@ public function testGetEnvReturnsStringFromGlobalServerIfPsrContainerHasNoEntry(
         $psr->expects($this->once())->method('has')->with('X_FOO')->willReturn(false);
         $psr->expects($this->never())->method('get');
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $_SERVER['X_FOO'] = 'bar';
@@ -2102,6 +2107,7 @@ public function testGetEnvThrowsIfMapPsrContainerReturnsInvalidType(): void
         $psr->expects($this->once())->method('has')->with('X_FOO')->willReturn(true);
         $psr->expects($this->once())->method('get')->with('X_FOO')->willReturn(42);
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $this->expectException(\TypeError::class);
@@ -2139,6 +2145,7 @@ public function testGetAccessLogHandlerReturnsAccessLogHandlerInstanceFromPsrCon
         $psr->expects($this->once())->method('has')->with(AccessLogHandler::class)->willReturn(true);
         $psr->expects($this->once())->method('get')->with(AccessLogHandler::class)->willReturn($accessLogHandler);
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $ret = $container->getAccessLogHandler();
@@ -2152,6 +2159,7 @@ public function testGetAccessLogHandlerReturnsDefaultAccessLogHandlerInstanceIfP
         $psr->expects($this->once())->method('has')->with(AccessLogHandler::class)->willReturn(false);
         $psr->expects($this->never())->method('get');
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $accessLogHandler = $container->getAccessLogHandler();
@@ -2189,6 +2197,7 @@ public function testGetErrorHandlerReturnsErrorHandlerInstanceFromPsrContainer()
         $psr->expects($this->once())->method('has')->with(ErrorHandler::class)->willReturn(true);
         $psr->expects($this->once())->method('get')->with(ErrorHandler::class)->willReturn($errorHandler);
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $ret = $container->getErrorHandler();
@@ -2202,6 +2211,7 @@ public function testGetErrorHandlerReturnsDefaultErrorHandlerInstanceIfPsrContai
         $psr->expects($this->once())->method('has')->with(ErrorHandler::class)->willReturn(false);
         $psr->expects($this->never())->method('get');
 
+        assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
         $errorHandler = $container->getErrorHandler();
diff --git a/tests/Io/RouteHandlerTest.php b/tests/Io/RouteHandlerTest.php
index c12e195..4f15d91 100644
--- a/tests/Io/RouteHandlerTest.php
+++ b/tests/Io/RouteHandlerTest.php
@@ -54,6 +54,7 @@ public function testMapRouteWithClassNameAddsRouteOnRouterWithControllerCallable
         $container = $this->createMock(Container::class);
         $container->expects($this->once())->method('callable')->with('stdClass')->willReturn($controller);
 
+        assert($container instanceof Container);
         $handler = new RouteHandler($container);
 
         $router = $this->createMock(RouteCollector::class);
@@ -98,6 +99,7 @@ public function testMapRouteWithContainerAndControllerClassNameAddsRouteOnRouter
         $ref->setAccessible(true);
         $ref->setValue($handler, $router);
 
+        assert($container instanceof Container);
         $handler->map(['GET'], '/', $container, \stdClass::class);
     }
 
diff --git a/tests/install-as-dep/composer.json b/tests/install-as-dep/composer.json
index d404fd2..a47dac7 100644
--- a/tests/install-as-dep/composer.json
+++ b/tests/install-as-dep/composer.json
@@ -1,7 +1,6 @@
 {
     "require": {
-        "clue/framework-x": "*@dev",
-        "react/async": "^4@dev || ^3@dev"
+        "clue/framework-x": "*@dev"
     },
     "repositories": [
         {