Auto-Inject into Test\Unit (Codeception#4070)

* allow to inject actor classes and other objects from DI into the Test\Unit via inject
deprecates using  $this->tester in favor of common _inject()

* fixed creating actor object via di

src/Codeception/Test/Unit.php

@@ -3,6 +3,7 @@
 
 use Codeception\Configuration;
 use Codeception\Exception\ModuleException;
+use Codeception\Lib\Di;
 use Codeception\Scenario;
 use Codeception\TestInterface;
 
@@ -39,14 +40,18 @@ protected function setUp()
             }
             return;
         }
-        $scenario = new Scenario($this);
-        $actorClass = $this->getMetadata()->getCurrent('actor');
-        if ($actorClass) {
-            $I = new $actorClass($scenario);
-            $property = lcfirst(Configuration::config()['actor']);
-            $this->$property = $I;
+
+        /** @var $di Di  **/
+        $di = $this->getMetadata()->getService('di');
+        $di->set(new Scenario($this));
+
+        // auto-inject $tester property
+        if (($this->getMetadata()->getCurrent('actor')) && ($property = lcfirst(Configuration::config()['actor']))) {
+            $this->$property = $di->instantiate($this->getMetadata()->getCurrent('actor'));
         }
-        $this->getMetadata()->getService('di')->injectDependencies($this); // injecting dependencies
+
+        // Auto inject into the _inject method
+        $di->injectDependencies($this); // injecting dependencies
         $this->_before();
     }