Implement withSharable()

src/Network/Response.php

@@ -1264,6 +1264,30 @@ public function sharable($public = null, $time = null)
         return (bool)$public;
     }
 
+    /**
+     * Create a new instace with the public/private Cache-Control directive set.
+     *
+     * @param bool $public If set to true, the Cache-Control header will be set as public
+     *   if set to false, the response will be set to private.
+     * @param int|null $time time in seconds after which the response should no longer be considered fresh.
+     * @return static
+     */
+    public function withSharable($public, $time = null)
+    {
+        $new = clone $this;
+        unset($new->_cacheDirectives['private'], $new->_cacheDirectives['public']);
+
+        $key = $public ? 'public' : 'private';
+        $new->_cacheDirectives[$key] = true;
+
+        if ($time !== null) {
+            $new->_cacheDirectives['max-age'] = $time;
+        }
+        $new->_setCacheControl();
+
+        return $new;
+    }
+
     /**
      * Sets the Cache-Control s-maxage directive.
      *

tests/TestCase/Network/ResponseTest.php

@@ -838,7 +838,19 @@ public function testSharable()
      */
     public function testWithSharable()
     {
-        $this->markTestIncomplete();
+        $response = new Response();
+        $new = $response->withSharable(true);
+        $this->assertFalse($response->hasHeader('Cache-Control'), 'old instance unchanged');
+        $this->assertEquals('public', $new->getHeaderLine('Cache-Control'));
+
+        $new = $response->withSharable(false);
+        $this->assertEquals('private', $new->getHeaderLine('Cache-Control'));
+
+        $new = $response->withSharable(true, 3600);
+        $this->assertEquals('public, max-age=3600', $new->getHeaderLine('Cache-Control'));
+
+        $new = $response->withSharable(false, 3600);
+        $this->assertEquals('private, max-age=3600', $new->getHeaderLine('Cache-Control'));
     }
 
     /**