diff --git a/tests/TestCase/Http/ResponseEmitterTest.php b/tests/TestCase/Http/ResponseEmitterTest.php
index 101be00f612..daf70040250 100644
--- a/tests/TestCase/Http/ResponseEmitterTest.php
+++ b/tests/TestCase/Http/ResponseEmitterTest.php
@@ -28,13 +28,30 @@ class ResponseEmitterTest extends TestCase
 {
     protected $emitter;
 
+    /**
+     * setup
+     *
+     * @return void
+     */
     public function setUp()
     {
         parent::setUp();
+        $GLOBALS['mockedHeadersSent'] = false;
         $GLOBALS['mockedHeaders'] = $GLOBALS['mockedCookies'] = [];
         $this->emitter = new ResponseEmitter();
     }
 
+    /**
+     * teardown
+     *
+     * @return void
+     */
+    public function tearDown()
+    {
+        parent::tearDown();
+        unset($GLOBALS['mockedHeadersSent']);
+    }
+
     /**
      * Test emitting simple responses.
      *
diff --git a/tests/TestCase/Http/ResponseTest.php b/tests/TestCase/Http/ResponseTest.php
index bac96c4240d..53714bc871c 100644
--- a/tests/TestCase/Http/ResponseTest.php
+++ b/tests/TestCase/Http/ResponseTest.php
@@ -46,6 +46,7 @@ public function setUp()
     {
         parent::setUp();
         $this->server = $_SERVER;
+        $GLOBALS['mockedHeadersSent'] = false;
     }
 
     /**
@@ -57,6 +58,7 @@ public function tearDown()
     {
         parent::tearDown();
         $_SERVER = $this->server;
+        unset($GLOBALS['mockedHeadersSent']);
     }
 
     /**
diff --git a/tests/TestCase/Http/ServerTest.php b/tests/TestCase/Http/ServerTest.php
index 3deeddd5eb0..3440411d6c5 100644
--- a/tests/TestCase/Http/ServerTest.php
+++ b/tests/TestCase/Http/ServerTest.php
@@ -42,6 +42,7 @@ public function setUp()
         $this->server = $_SERVER;
         $this->config = dirname(dirname(__DIR__));
         $GLOBALS['mockedHeaders'] = [];
+        $GLOBALS['mockedHeadersSent'] = false;
     }
 
     /**
@@ -53,6 +54,7 @@ public function tearDown()
     {
         parent::tearDown();
         $_SERVER = $this->server;
+        unset($GLOBALS['mockedHeadersSent']);
     }
 
     /**
diff --git a/tests/TestCase/Http/server_mocks.php b/tests/TestCase/Http/server_mocks.php
index 60a2c33f61b..24a5582ebd9 100644
--- a/tests/TestCase/Http/server_mocks.php
+++ b/tests/TestCase/Http/server_mocks.php
@@ -6,7 +6,7 @@
 
 function headers_sent()
 {
-    return false;
+    return isset($GLOBALS['mockedHeadersSent']) ? $GLOBALS['mockedHeadersSent'] : true;
 }
 
 function header($header)