minor #22099 HttpCache: New test for revalidating responses with an e…

…xpired TTL (mpdude)

This PR was squashed before being merged into the 2.7 branch (closes #22099).

Discussion
----------

HttpCache: New test for revalidating responses with an expired TTL

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

See #22035, in particular [this and the following comments](symfony/symfony#22035 (comment)).

Commits
-------

067ab52 HttpCache: New test for revalidating responses with an expired TTL

Tests/HttpCache/HttpCacheTest.php

@@ -849,6 +849,42 @@ public function testValidatesCachedResponsesWithETagAndNoFreshnessInformation()
         $this->assertTraceNotContains('miss');
     }
 
+    public function testServesResponseWhileFreshAndRevalidatesWithLastModifiedInformation()
+    {
+        $time = \DateTime::createFromFormat('U', time());
+
+        $this->setNextResponse(200, array(), 'Hello World', function (Request $request, Response $response) use ($time) {
+            $response->setSharedMaxAge(10);
+            $response->headers->set('Last-Modified', $time->format(DATE_RFC2822));
+        });
+
+        // prime the cache
+        $this->request('GET', '/');
+
+        // next request before s-maxage has expired: Serve from cache
+        // without hitting the backend
+        $this->request('GET', '/');
+        $this->assertHttpKernelIsNotCalled();
+        $this->assertEquals(200, $this->response->getStatusCode());
+        $this->assertEquals('Hello World', $this->response->getContent());
+        $this->assertTraceContains('fresh');
+
+        sleep(15); // expire the cache
+
+        $that = $this;
+
+        $this->setNextResponse(304, array(), '', function (Request $request, Response $response) use ($time, $that) {
+            $that->assertEquals($time->format(DATE_RFC2822), $request->headers->get('IF_MODIFIED_SINCE'));
+        });
+
+        $this->request('GET', '/');
+        $this->assertHttpKernelIsCalled();
+        $this->assertEquals(200, $this->response->getStatusCode());
+        $this->assertEquals('Hello World', $this->response->getContent());
+        $this->assertTraceContains('stale');
+        $this->assertTraceContains('valid');
+    }
+
     public function testReplacesCachedResponsesWhenValidationResultsInNon304Response()
     {
         $time = \DateTime::createFromFormat('U', time());