qa: provide tests for LazyListener

Creates LazyListenerTest to validate all behaviors of LazyListener. In
the process, found an issue with `getListener()` where I was accessing
an undeclared variable instead of an instance property.

Author: weierophinney

src/LazyListener.php

@@ -76,7 +76,7 @@ private function getListener($service) : callable
 
         // Object, method present, but method is not callable: invalid
         if (! is_callable($callback)) {
-            throw Exception\InvalidListenerException::forNonCallableInstanceMethod($service, $method);
+            throw Exception\InvalidListenerException::forNonCallableInstanceMethod($service, $this->method);
         }
 
         // Object with method as callback

test/LazyListenerTest.php

@@ -0,0 +1,75 @@
+<?php
+/**
+ * @see       https://github.com/phly/phly-event-dispatcher for the canonical source repository
+ * @copyright Copyright (c) 2018-2019 Matthew Weier O'Phinney (https:/mwop.net)
+ * @license   https://github.com/phly/phly-event-dispatcher/blob/master/LICENSE.md New BSD License
+ */
+
+declare(strict_types=1);
+
+namespace PhlyTest\EventDispatcher;
+
+use Phly\EventDispatcher\Exception\InvalidListenerException;
+use Phly\EventDispatcher\LazyListener;
+use PHPUnit\Framework\TestCase;
+use Psr\Container\ContainerInterface;
+
+class LazyListenerTest extends TestCase
+{
+    public function setUp()
+    {
+        $this->event = new TestAsset\TestEvent();
+        $this->container = $this->prophesize(ContainerInterface::class);
+    }
+
+    public function testRaisesExceptionIfServiceReturnedIsNeitherAnObjectNorCallable()
+    {
+        $this->container->get('LazyService')->willReturn('not-callable');
+        $lazyListener = new LazyListener($this->container->reveal(), 'LazyService');
+
+        $this->expectException(InvalidListenerException::class);
+        $lazyListener($this->event);
+    }
+
+    public function testInvokesNonObjectCallableListenerReturnedByContainer()
+    {
+        $this->container->get('LazyService')->willReturn(__NAMESPACE__ . '\TestAsset\listenerFunction');
+        $lazyListener = new LazyListener($this->container->reveal(), 'LazyService');
+
+        $this->assertNull($lazyListener($this->event));
+    }
+
+    public function testRaisesExceptionIfObjectServiceReturnedIsNotCallableAndNoMethodProvided()
+    {
+        $this->container->get('LazyService')->willReturn((object) []);
+        $lazyListener = new LazyListener($this->container->reveal(), 'LazyService');
+
+        $this->expectException(InvalidListenerException::class);
+        $lazyListener($this->event);
+    }
+
+    public function testInvokesCallableListenerReturnedByContainerWhenNoMethodProvided()
+    {
+        $this->container->get('LazyService')->willReturn(new TestAsset\Listener());
+        $lazyListener = new LazyListener($this->container->reveal(), 'LazyService');
+
+        $this->assertNull($lazyListener($this->event));
+    }
+
+    public function testRaisesExceptionIfObjectServiceReturnedIsNotCallableViaMethodProvided()
+    {
+        $this->container->get('LazyService')->willReturn(new TestAsset\Listener());
+        $lazyListener = new LazyListener($this->container->reveal(), 'LazyService', 'not-a-real-method');
+
+        $this->expectException(InvalidListenerException::class);
+        $lazyListener($this->event);
+    }
+
+    public function testInvokesMethodOnObjectListenerReturnedByContainer()
+    {
+        $this->container->get('LazyService')->willReturn(new TestAsset\Listener());
+        $lazyListener = new LazyListener($this->container->reveal(), 'LazyService', 'onTest');
+
+        $this->assertNull($lazyListener($this->event));
+    }
+}