Create initial versions of the context and trait that allow to inspect the page cache.

Author: pfrenssen

src/Context/PageCacheContext.php

@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace DrupalTest\BehatTraits\Context;
+
+use Behat\MinkExtension\Context\RawMinkContext;
+use DrupalTest\BehatTraits\Traits\PageCacheTrait;
+use PHPUnit\Framework\Assert;
+
+/**
+ * Provides example step definitions that interact with the page cache.
+ *
+ * These step definitions are mainly intended as an example implementation, and
+ * for verifying that the trait is working correctly. They might however also be
+ * useful in real life projects. If this is the case, feel free to include this
+ * context class in your `behat.yml` file so you can use the provided steps in
+ * your user scenarios.
+ *
+ * @see \DrupalTest\BehatTraits\Traits\PageCacheTrait
+ */
+class PageCacheContext extends RawMinkContext {
+
+  use PageCacheTrait;
+
+  /**
+   * Checks that the page is cacheable.
+   *
+   * @Then the page should be cacheable
+   */
+  public function assertPageCacheable(): void {
+    Assert::assertTrue($this->isPageCacheable());
+  }
+
+  /**
+   * Checks that the page is not cacheable.
+   *
+   * @Then the page should not be cacheable
+   */
+  public function assertPageNotCacheable(): void {
+    Assert::assertFalse($this->isPageCacheable());
+  }
+
+  /**
+   * Checks that the page is cached.
+   *
+   * @Then the page should be cached
+   */
+  public function assertPageCached(): void {
+    Assert::assertTrue($this->isPageCached());
+  }
+
+  /**
+   * Checks that the page is not cached.
+   *
+   * @Then the page should not be cached
+   */
+  public function assertPageNotCached(): void {
+    Assert::assertFalse($this->isPageCached());
+  }
+
+}

src/Traits/PageCacheTrait.php

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+<?php
+
+declare(strict_types = 1);
+
+namespace DrupalTest\BehatTraits\Traits;
+
+use Behat\MinkExtension\Context\RawMinkContext;
+
+/**
+ * Helper methods to inspect the cache status of the current page.
+ *
+ * These methods report if the current page is cached or cacheable by Drupal's
+ * page cache and dynamic page cache. The standard page cache is used for
+ * anonymous users without a session, while the dynamic page cache is used for
+ * authenticated users and anonymous users with a session (e.g. anonymous users
+ * with a shopping cart).
+ *
+ * This relies on the following setting to be enabled in `services.yml`:
+ *   http.response.debug_cacheability_headers: true
+ */
+trait PageCacheTrait {
+
+  /**
+   * Returns the cache status of Drupal's page cache and dynamic page cache.
+   *
+   * @return array
+   *   An associative array with the following keys:
+   *   - X-Drupal-Cache: the status of Drupal's page cache. Can be one of:
+   *     - 'HIT': The page is served from the page cache.
+   *     - 'MISS': The page is not currently served from the page cache, but is
+   *       cacheable and subsequent requests will be served from cache.
+   *     - NULL: The page could not be served from the page cache. This may be
+   *       because either the page_cache module is not enabled, the user has a
+   *       session, or the page is not cacheable.
+   *   - X-Drupal-Dynamic-Cache: the status of the dynamic page cache. One of:
+   *     - 'HIT': The page is served from the dynamic page cache.
+   *     - 'MISS': The page is not currently served from the page cache, but is
+   *       cacheable and subsequent requests will be served from cache.
+   *     - 'UNCACHEABLE': The page is uncacheable because it meets one or more
+   *       of the conditions as defined in the `auto_placeholder_conditions`
+   *       setting in `services.yml`.
+   *     - NULL: The page could not be handled by the dynamic page cache. This
+   *       can be because of various reasons: the dynamic_page_cache module is
+   *       not enabled, the page has a 403 or 404 status, or one of the request
+   *       or response policies are not met.
+   */
+  protected function getPageCacheStatus(): array {
+    assert($this instanceof RawMinkContext, __METHOD__ . ' should only be included in Context classes that extend RawMinkContext.');
+
+    /** @var \Behat\Mink\Session $session */
+    $session = $this->getSession();
+
+    return [
+      'X-Drupal-Cache' => $session->getResponseHeader('X-Drupal-Cache'),
+      'X-Drupal-Dynamic-Cache' => $session->getResponseHeader('X-Drupal-Dynamic-Cache'),
+    ];
+  }
+
+  /**
+   * Returns whether the current page is served from the cache.
+   *
+   * This can be either from the page cache or dynamic page cache.
+   *
+   * @return bool
+   *   TRUE if the current page is served from the cache.
+   */
+  protected function isPageCached(): bool {
+    return in_array('HIT', $this->getPageCacheStatus());
+  }
+
+  /**
+   * Returns whether the current page is cacheable.
+   *
+   * @return bool
+   *   TRUE if the current page is served from the cache, or eligible to be
+   *   served from the cache on subsequent requests.
+   */
+  protected function isPageCacheable(): bool {
+    return $this->isPageCached() || in_array('MISS', $this->getPageCacheStatus());
+  }
+
+}