Add Behat support

- `BrowserOptions` (readonly value object) — env-var-driven configuration
- `BrowserRegistry` — replaces the static state previously held by `LegacyExtension`
- `KernelBooter` interface + `Test/PhpUnitKernelBooter` (closure-fed, captures the trait's privileged scope)
- `BrowserFactory` — builds `KernelBrowser` / `PantherBrowser` from a booter
- `Artifact/{ArtifactSink, ArtifactCollector, EchoArtifactSink, FailureType}` — the lifecycle/artifact-capture logic extracted out of `LegacyExtension`

- `HasBrowser` trait: now ~95 lines, delegates to `BrowserFactory` with closures granting protected-static access
- `LegacyExtension` / `BootstrappedExtension`: thin adapters forwarding events to `ArtifactCollector`
- `BrowserExtension`: unchanged externally — same `phpunit.xml.dist` snippet works

- `BrowserExtension` — Behat `ServiceContainer` Extension wiring everything
- `Context/{BrowserAware, BrowserAwareTrait}` — drop-in analog of `HasBrowser`
- `Initializer/BrowserContextInitializer` — injects services via Behat's standard DI
- `EventListener/ArtifactListener` — Suite + Scenario events drive `ArtifactCollector`
- `Output/BehatOutputArtifactSink` — STDOUT-direct summary writer
- `Kernel/{KernelBooter implementations}` — `StandaloneKernelBooter` (env-var) and `SymfonyExtensionKernelBooter` (FoB), selected at compile time via class_exists; PantherClientFactory adapter to bypass Panther's protected statics

- `composer.json`: `behat/behat ^3.13|^4.0@dev` added to `require-dev`; both behat and FoB extension listed in suggest
- `tests/Behat/{behat.dist.php, behat.yml.dist, Context/BrowserContext.php, features/browser.feature}` — exercises the bridge end-to-end against the existing fixture kernel
- `README.md`: new "Using with Behat" section with context + config examples

Known caveat documented in the plan: `friends-of-behat/symfony-extension` doesn't yet support Symfony 8, so I could only end-to-end verify the `StandaloneKernelBooter` path. The `SymfonyExtensionKernelBooter` is code-complete and PHPStan-clean, but will need either a downgraded composer profile or a FoB release that supports Symfony 8 to verify in CI. The class is wired conditionally so it doesn't break consumers without FoB installed.

Author: hhamon

README.md

@@ -547,6 +547,73 @@ class MyTest extends PantherTestCase
 }
 ```
 
+### Using with Behat
+
+The same fluent browser API is available inside a Behat scenario via the `Zenstruck\Browser\Bridge\Behat\BrowserExtension` and the `BrowserAwareTrait`:
+
+```php
+// features/bootstrap/BrowserContext.php
+namespace App\Tests\Behat;
+
+use Behat\Behat\Context\Context;
+use Behat\Step\When;
+use Behat\Step\Then;
+use Zenstruck\Browser\Bridge\Behat\Context\BrowserAware;
+use Zenstruck\Browser\Bridge\Behat\Context\BrowserAwareTrait;
+
+final class BrowserContext implements Context, BrowserAware
+{
+    use BrowserAwareTrait;
+
+    #[When('I visit :url')]
+    public function iVisit(string $url): void
+    {
+        $this->browser()->visit($url);
+    }
+
+    #[Then('I should see :text')]
+    public function iShouldSee(string $text): void
+    {
+        $this->browser()->assertSee($text);
+    }
+}
+```
+
+Register the extension in `behat.dist.php` (Behat 4) or `behat.yml.dist` (Behat 3):
+
+```php
+// behat.dist.php (Behat 4)
+use Behat\Config\Config;
+use Behat\Config\Extension;
+use Behat\Config\Profile;
+use Behat\Config\Suite;
+
+return (new Config())
+    ->withProfile(
+        (new Profile('default'))
+            ->withSuite(
+                (new Suite('default'))
+                    ->withPaths(__DIR__.'/features')
+                    ->withContexts(App\Tests\Behat\BrowserContext::class),
+            )
+            ->withExtension(new Extension(Zenstruck\Browser\Bridge\Behat\BrowserExtension::class, [
+                'kernel_class' => App\Kernel::class,
+                'env' => 'test',
+                'debug' => true,
+            ]))
+    )
+;
+```
+
+The Behat extension picks its Symfony kernel boot strategy automatically:
+
+- If `friends-of-behat/symfony-extension` is installed and enabled in the same Behat config, the kernel is consumed from that extension (`SymfonyExtensionKernelBooter`).
+- Otherwise the kernel is booted directly from the `kernel_class` config key (`StandaloneKernelBooter`), defaulting to the `KERNEL_CLASS` env var when not provided.
+
+Each scenario starts with a fresh kernel (reboot between scenarios), and the same artifact-capture-on-failure behavior (screenshots, HTML dumps) wired into PHPUnit is also wired into the Behat scenario lifecycle.
+
+> **Note:** Using `PantherBrowser` from Behat additionally requires `symfony/panther`, which itself pulls in `phpunit/phpunit`.
+
 ## Configuration
 
 There are several environment variables available to configure:

composer.json

@@ -22,6 +22,7 @@
         "zenstruck/callback": "^1.4.2"
     },
     "require-dev": {
+        "behat/behat": "^3.13|^4.0@dev",
         "dbrekelmans/bdi": "^1.0",
         "justinrainbow/json-schema": "^5.3",
         "mtdowling/jmespath.php": "^2.6",
@@ -34,6 +35,8 @@
         "symfony/security-bundle": "^6.4|^7.0|^8.0"
     },
     "suggest": {
+        "behat/behat": "To use the Behat bridge under Zenstruck\\Browser\\Bridge\\Behat.",
+        "friends-of-behat/symfony-extension": "To boot the Symfony kernel under Behat via SymfonyExtensionKernelBooter (otherwise the StandaloneKernelBooter is used).",
         "justinrainbow/json-schema": "Json schema validator. Needed to use Json::assertMatchesSchema().",
         "mtdowling/jmespath.php":  "PHP implementation for JMESPath. Needed to use Json assertions."
     },
@@ -45,7 +48,10 @@
         "psr-4": { "Zenstruck\\": "src/" }
     },
     "autoload-dev": {
-        "psr-4": { "Zenstruck\\Browser\\Tests\\": "tests/" }
+        "psr-4": {
+            "Zenstruck\\Browser\\Tests\\": "tests/",
+            "Zenstruck\\Browser\\Tests\\Behat\\": "tests/Behat/"
+        }
     },
     "minimum-stability": "dev",
     "prefer-stable": true

src/Browser/Artifact/ArtifactCollector.php

@@ -0,0 +1,103 @@
+<?php
+
+/*
+ * This file is part of the zenstruck/browser package.
+ *
+ * (c) Kevin Bond <kevinbond@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Zenstruck\Browser\Artifact;
+
+use Zenstruck\Browser\BrowserRegistry;
+
+/**
+ * Drives the test-or-scenario lifecycle that captures browser state on failure
+ * and accumulates the "Saved Browser Artifacts" summary printed at end of suite.
+ * Test-runner-agnostic: PHPUnit and Behat each wire their own events to these
+ * methods.
+ *
+ * @author Hugo Hamon <hello@kodero.fr>
+ */
+final class ArtifactCollector
+{
+    /** @var array<string, array<string, string[]>> */
+    private array $savedArtifacts = [];
+
+    public function __construct(
+        private readonly BrowserRegistry $registry,
+        private readonly ArtifactSink $sink,
+    ) {
+    }
+
+    public function onSuiteStart(): void
+    {
+        $this->registry->start();
+    }
+
+    public function onScenarioStart(string $name): void
+    {
+        $this->registry->clear();
+    }
+
+    public function onScenarioFailed(string $name, FailureType $type): void
+    {
+        if ($this->registry->isEmpty()) {
+            return;
+        }
+
+        $filename = \sprintf('%s_%s', $type->value, self::normalizeName($name));
+
+        foreach ($this->registry->all() as $i => $browser) {
+            try {
+                $browser->saveCurrentState("{$filename}__{$i}");
+            } catch (\Throwable) {
+                // swallow exceptions related to dumping the current state so as to not
+                // lose the actual error/failure being reported by the test runner
+            }
+        }
+    }
+
+    public function onScenarioFinish(string $name): void
+    {
+        foreach ($this->registry->all() as $browser) {
+            foreach ($browser->savedArtifacts() as $category => $artifacts) {
+                if (\count($artifacts) === 0) {
+                    continue;
+                }
+
+                $this->savedArtifacts[$name][$category] = $artifacts;
+            }
+        }
+
+        $this->registry->clear();
+    }
+
+    public function onSuiteFinish(): void
+    {
+        $this->sink->writeSummary($this->savedArtifacts);
+        $this->registry->stop();
+    }
+
+    private static function normalizeName(string $name): string
+    {
+        if (!\mb_strstr($name, 'with data set')) {
+            return \strtr($name, '\\:', '-_');
+        }
+
+        // Try to match for a numeric data set index. If it didn't, match for a string one.
+        if (!\preg_match('#^(?<test>[\w:\\\]+) with data set \#(?<dataset>\d+)#', $name, $matches)) {
+            \preg_match('#^(?<test>[\w:\\\]+) with data set "(?<dataset>.*)"#', $name, $matches);
+        }
+
+        $normalized = \strtr($matches['test'], '\\:', '-_');
+
+        if (isset($matches['dataset'])) {
+            $normalized .= '__data-set-'.\preg_replace('/\W+/', '-', $matches['dataset']);
+        }
+
+        return $normalized;
+    }
+}

src/Browser/Artifact/ArtifactSink.php

@@ -0,0 +1,27 @@
+<?php
+
+/*
+ * This file is part of the zenstruck/browser package.
+ *
+ * (c) Kevin Bond <kevinbond@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Zenstruck\Browser\Artifact;
+
+/**
+ * Destination for the end-of-suite "Saved Browser Artifacts" summary. PHPUnit
+ * uses {@see EchoArtifactSink}; Behat ships a sink that writes through Behat's
+ * output printer instead of plain echo.
+ *
+ * @author Hugo Hamon <hello@kodero.fr>
+ */
+interface ArtifactSink
+{
+    /**
+     * @param array<string, array<string, string[]>> $savedArtifacts indexed by test name then category
+     */
+    public function writeSummary(array $savedArtifacts): void;
+}

src/Browser/Artifact/EchoArtifactSink.php

@@ -0,0 +1,42 @@
+<?php
+
+/*
+ * This file is part of the zenstruck/browser package.
+ *
+ * (c) Kevin Bond <kevinbond@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Zenstruck\Browser\Artifact;
+
+/**
+ * Preserves the historical PHPUnit-extension output: a plain `echo` of the
+ * "Saved Browser Artifacts" summary at end of suite.
+ *
+ * @author Hugo Hamon <hello@kodero.fr>
+ */
+final class EchoArtifactSink implements ArtifactSink
+{
+    public function writeSummary(array $savedArtifacts): void
+    {
+        if ($savedArtifacts === []) {
+            return;
+        }
+
+        echo "\n\nSaved Browser Artifacts:";
+
+        foreach ($savedArtifacts as $test => $categories) {
+            echo "\n\n  {$test}";
+
+            foreach ($categories as $category => $artifacts) {
+                echo "\n    {$category}:";
+
+                foreach ($artifacts as $artifact) {
+                    echo "\n      * {$artifact}:";
+                }
+            }
+        }
+    }
+}

src/Browser/Artifact/FailureType.php

@@ -0,0 +1,25 @@
+<?php
+
+/*
+ * This file is part of the zenstruck/browser package.
+ *
+ * (c) Kevin Bond <kevinbond@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Zenstruck\Browser\Artifact;
+
+/**
+ * Distinguishes the two failure flavors PHPUnit reports: errors (unexpected
+ * exceptions) and failures (assertion failures). The backed value is used as
+ * the filename prefix when dumping a browser's state on failure.
+ *
+ * @author Hugo Hamon <hello@kodero.fr>
+ */
+enum FailureType: string
+{
+    case Error = 'error';
+    case Failure = 'failure';
+}