Add callback to stub responses

src/Zttp.php

@@ -4,10 +4,35 @@
 
 class Zttp
 {
+    static $expectations;
+
     static function __callStatic($method, $args)
     {
         return PendingZttpRequest::new()->{$method}(...$args);
     }
+
+    static function stub($callback)
+    {
+        self::$expectations = collect($callback);
+    }
+
+    static function clearStubs()
+    {
+        self::$expectations = null;
+    }
+
+    static function stubHandler()
+    {
+        return function ($handler) {
+            return function ($request, $options) use ($handler) {
+                return (self::$expectations ?? collect())
+                    ->map
+                    ->__invoke(new ZttpRequest($request), $options)
+                    ->filter()
+                    ->first(null, $handler($request, $options));
+            };
+        };
+    }
 }
 
 class PendingZttpRequest
@@ -114,7 +139,7 @@ function withDigestAuth($username, $password)
 
     function withCookies($cookies)
     {
-        return tap($this, function($request) use ($cookies) {
+        return tap($this, function ($request) use ($cookies) {
             return $this->options = array_merge_recursive($this->options, [
                 'cookies' => $cookies,
             ]);
@@ -199,6 +224,7 @@ function buildHandlerStack()
     {
         return tap(\GuzzleHttp\HandlerStack::create(), function ($stack) {
             $stack->push($this->buildBeforeSendingHandler());
+            $stack->push(Zttp::stubHandler());
         });
     }
 
@@ -349,6 +375,14 @@ function __call($method, $args)
     }
 }
 
+class ZttpResponseStub extends ZttpResponse
+{
+    static function create($body = null, $status = 200, $headers = [])
+    {
+        return \GuzzleHttp\Promise\promise_for(new \GuzzleHttp\Psr7\Response($status, $headers, $body));
+    }
+}
+
 class ConnectionException extends \Exception {}
 
 function tap($value, $callback) {

tests/ZttpTest.php

@@ -1,8 +1,8 @@
 <?php
 
+use PHPUnit\Framework\TestCase;
 use Zttp\Zttp;
 use Zttp\ZttpResponse;
-use PHPUnit\Framework\TestCase;
 
 class ZttpTest extends TestCase
 {
@@ -11,6 +11,12 @@ public static function setUpBeforeClass()
         ZttpServer::start();
     }
 
+    protected function tearDown()
+    {
+        Zttp::clearStubs();
+        parent::tearDown();
+    }
+
     function url($url)
     {
         return vsprintf('%s/%s', [
@@ -474,9 +480,9 @@ function response_can_use_macros()
     /** @test */
     function can_use_basic_auth()
     {
-       $response = Zttp::withBasicAuth('zttp', 'secret')->get($this->url('/basic-auth'));
+        $response = Zttp::withBasicAuth('zttp', 'secret')->get($this->url('/basic-auth'));
 
-       $this->assertTrue($response->isOk());
+        $this->assertTrue($response->isOk());
     }
 
     /** @test */
@@ -518,6 +524,79 @@ function cookies_can_be_shared_between_requests()
         $response = Zttp::get($this->url('/get'));
         $this->assertEquals([], $response->json()['cookies']);
     }
+
+    /** @test */
+    function responses_can_be_stubbed()
+    {
+        Zttp::stub(function ($request, $options) {
+            return \Zttp\ZttpResponseStub::create('stubbed ' . $request->method() . ' response');
+        });
+
+        $this->assertEquals('stubbed GET response', Zttp::get('/foo')->body());
+        $this->assertEquals('stubbed POST response', Zttp::post('/bar')->body());
+        $this->assertEquals('stubbed PUT response', Zttp::put('/baz')->body());
+    }
+
+    /** @test */
+    function responses_can_be_stubbed_and_unstubbed()
+    {
+        Zttp::stub(function ($request, $options) {
+            return \Zttp\ZttpResponseStub::create('stubbed response');
+        });
+
+        $stubbedResponse = Zttp::get($this->url('/get'));
+        $this->assertEquals($stubbedResponse, $stubbedResponse->body());
+
+        Zttp::clearStubs();
+
+        $response = Zttp::get($this->url('/get'));
+        $this->assertNotEquals('stubbed response', $response->body());
+    }
+
+    /** @test */
+    function responses_which_are_not_stubbed_are_sent()
+    {
+        Zttp::stub(function ($request, $options) {
+            if ($request->method() === 'POST') {
+                return \Zttp\ZttpResponseStub::create('stubbed response');
+            }
+        });
+
+        $stubbedResponse = Zttp::post('/stubbed');
+        $this->assertEquals('stubbed response', $stubbedResponse->body());
+
+        $this->assertNotEquals('stubbed response', Zttp::get($this->url('/get'))->body());
+    }
+
+    /** @test */
+    function stub_callback_is_fired_after_other_callbacks()
+    {
+        $fired = false;
+        Zttp::stub(function ($request, $options) use (&$fired) {
+            if ($fired) {
+                return \Zttp\ZttpResponseStub::create('stubbed response');
+            }
+        });
+
+        $response = Zttp::beforeSending(function ($request, $options) use (&$fired) {
+            $fired = true;
+        })->get('/get');
+
+        $this->assertEquals('stubbed response', $response->body());
+    }
+
+    /**
+     * @test
+     * @expectedException \Zttp\ConnectionException
+     */
+    function stub_callback_can_throw_an_exception()
+    {
+        Zttp::stub(function ($request, $options) {
+            throw new \Zttp\ConnectionException();
+        });
+
+        Zttp::get('/oops');
+    }
 }
 
 class ZttpServer