Add tests for When::lazy

Author: jsor

tests/React/Promise/WhenLazyTest.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace React\Promise;
+
+/**
+ * @group When
+ * @group WhenLazy
+ */
+class WhenLazyTest extends TestCase
+{
+    /** @test */
+    public function shouldReturnALazyPromise()
+    {
+        $this->assertInstanceOf('React\\Promise\\PromiseInterface',  When::lazy(function () {}));
+    }
+
+    /** @test */
+    public function shouldCallFactoryIfThenIsInvoked()
+    {
+        $factory = $this->createCallableMock();
+        $factory
+            ->expects($this->once())
+            ->method('__invoke');
+
+        When::lazy($factory)
+            ->then();
+    }
+}