Make tests phpunit 7 compatible

Author: rvdbogerd

tests/Client/Client12RequestResponsesTest.php

@@ -406,12 +406,15 @@ public function testSerializerContextParametersAreAdded()
         $this->handlerRegistry->registerHandler(GraphNavigator::DIRECTION_SERIALIZATION, \Ex\SoapEnvelope12\Messages\GetSimpleInput::class, 'xml',
             function($visitor, \Ex\SoapEnvelope12\Messages\GetSimpleInput $obj, array $type, Context $context) {
 
-                self::assertTrue($context->hasAttribute('soapEndpoint'), 'The "soapEndpoint" attribute was not found on the context object');
-                self::assertEquals('http://www.example.org/12', $context->getAttribute('soapEndpoint'));
+                $this->assertTrue($context->hasAttribute('soapEndpoint'), 'The "soapEndpoint" attribute was not found on the context object');
+                $this->assertEquals('http://www.example.org/12', $context->getAttribute('soapEndpoint'));
 
-                self::assertTrue($context->hasAttribute('soapOperation'), 'The "soapOperation" attribute was not found on the context object');
-                self::assertIsArray($context->getAttribute('soapOperation'));
-                self::assertEquals('http://www.example.org/test/getSimple', $context->getAttribute('soapOperation')['action']);
+                $this->assertTrue($context->hasAttribute('soapOperation'), 'The "soapOperation" attribute was not found on the context object');
+                $this->assertTrue(
+                    is_array($context->getAttribute('soapOperation')),
+                    'The "soapOperation" attribute is not of type array, but '.gettype($context->getAttribute('soapOperation'))
+                );
+                $this->assertEquals('http://www.example.org/test/getSimple', $context->getAttribute('soapOperation')['action']);
 
                 throw new SerializerHandlerAssertionsWereExecuted('Stop serialization, test has finished');
             }
@@ -420,7 +423,7 @@ function($visitor, \Ex\SoapEnvelope12\Messages\GetSimpleInput $obj, array $type,
         $client = $this->getClient();
 
         // Assert that subscribing handler with assertions was executed
-        self::expectException(SerializerHandlerAssertionsWereExecuted::class);
+        $this->expectException(SerializerHandlerAssertionsWereExecuted::class);
 
         $client->getSimple('foo');
     }