$this->assertResponse(200);
$this->assertIdentical($edit['content'], $content, 'Response content matches');
$this->assertIdentical('invoked', $this->drupalGetHeader('X-Form-Test-Response-Event'), 'Response handled by kernel response subscriber');
$this->assertResponse(200);
$this->assertIdentical($edit['content'], $content, 'Response content matches');
$this->assertIdentical('invoked', $this->drupalGetHeader('X-Form-Test-Response-Event'), 'Response handled by kernel response subscriber');