[feature] fail if trying to manipulate an "exception" page (#81)

composer.json

@@ -16,6 +16,7 @@
         "behat/mink": "^1.8",
         "symfony/browser-kit": "^5.4|^6.0",
         "symfony/css-selector": "^5.4|^6.0",
+        "symfony/dom-crawler": "^5.4|^6.0",
         "symfony/framework-bundle": "^5.4|^6.0",
         "symfony/polyfill-php80": "^1.20",
         "zenstruck/assert": "^1.0",

src/Browser/KernelBrowser.php

@@ -313,7 +313,9 @@ final public function clickAndIntercept(string $selector): self
      */
     final public function assertStatus(int $expected): self
     {
-        $this->session()->assert()->statusCodeEquals($expected);
+        Assert::that($this->session()->getStatusCode())
+            ->is($expected, 'Current response status code is {actual}, but {expected} expected.')
+        ;
 
         return $this;
     }

src/Browser/Session.php

@@ -8,6 +8,7 @@
 use Behat\Mink\WebAssert;
 use Symfony\Component\BrowserKit\AbstractBrowser;
 use Symfony\Component\DomCrawler\Crawler;
+use Zenstruck\Assert as ZenstruckAssert;
 use Zenstruck\Browser\Session\Assert;
 use Zenstruck\Browser\Session\Driver;
 
@@ -40,11 +41,15 @@ public function client(): AbstractBrowser
 
     public function assert(): Assert
     {
+        $this->ensureNoException();
+
         return new Assert(new WebAssert($this));
     }
 
     public function page(): DocumentElement
     {
+        $this->ensureNoException();
+
         return $this->getPage();
     }
 
@@ -135,4 +140,24 @@ public function exit(): void
         $this->getDriver()->quit();
         exit(1);
     }
+
+    private function ensureNoException(): void
+    {
+        if (!$this->isStarted()) {
+            ZenstruckAssert::fail('A request has not yet been made.');
+        }
+
+        $crawler = $this->client()->getCrawler();
+
+        if (!\count($exceptionClassNode = $crawler->filter('.trace-details .trace-class')->first())) {
+            return;
+        }
+
+        $messageNode = $crawler->filter('.exception-message-wrapper .exception-message')->first();
+
+        ZenstruckAssert::fail('The last request threw an exception: %s - %s', [
+            \preg_replace('/\s+/', '', $exceptionClassNode->text()),
+            \count($messageNode) ? $messageNode->text() : 'unknown message',
+        ]);
+    }
 }

tests/BrowserTests.php

@@ -2,12 +2,14 @@
 
 namespace Zenstruck\Browser\Tests;
 
+use PHPUnit\Framework\AssertionFailedError;
 use Symfony\Component\BrowserKit\AbstractBrowser;
 use Symfony\Component\BrowserKit\Cookie;
 use Symfony\Component\BrowserKit\CookieJar;
 use Symfony\Component\DomCrawler\Crawler;
 use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\VarDumper\VarDumper;
+use Zenstruck\Assert;
 use Zenstruck\Browser;
 use Zenstruck\Browser\Test\HasBrowser;
 use Zenstruck\Browser\Tests\Fixture\TestComponent1;
@@ -601,6 +603,33 @@ public function can_access_the_html_crawler(): void
         $this->assertCount(2, $crawler);
     }
 
+    /**
+     * @test
+     */
+    public function fails_if_trying_to_manipulate_exception_page(): void
+    {
+        Assert::that(function() {
+            $this->browser()
+                ->visit('/exception')
+                ->click('foo')
+            ;
+        })->throws(AssertionFailedError::class, 'The last request threw an exception: Zenstruck\Browser\Tests\Fixture\CustomException - exception thrown');
+
+        Assert::that(function() {
+            $this->browser()
+                ->visit('/exception')
+                ->fillField('foo', 'bar')
+            ;
+        })->throws(AssertionFailedError::class, 'The last request threw an exception: Zenstruck\Browser\Tests\Fixture\CustomException - exception thrown');
+
+        Assert::that(function() {
+            $this->browser()
+                ->visit('/exception')
+                ->assertSee('foo')
+            ;
+        })->throws(AssertionFailedError::class, 'The last request threw an exception: Zenstruck\Browser\Tests\Fixture\CustomException - exception thrown');
+    }
+
     protected static function catchFileContents(string $expectedFile, callable $callback): string
     {
         (new Filesystem())->remove($expectedFile);

tests/Fixture/CustomException.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Zenstruck\Browser\Tests\Fixture;
+
+/**
+ * @author Kevin Bond <[email protected]>
+ */
+final class CustomException extends \RuntimeException
+{
+}

tests/Fixture/Kernel.php

@@ -108,7 +108,7 @@ public function json(Request $request): JsonResponse
 
     public function exception(): void
     {
-        throw new \Exception('exception thrown');
+        throw new CustomException('exception thrown');
     }
 
     public function redirect1(): RedirectResponse