Create a simpletest test to add additional form elements using the "Add another item" button

Question

I am trying to create a test case for my custom module using simpletest in Drupal7. I want to create a node. The problem is that the node edit form contains a number of fields which can have multiple values. Addition values are added by clicking on the "Add another item" button, which adds an addition field (nothing fancy here, just the standard Drupal form behavior).

I would like to create a node with two values for email. By default the node form only displays one email field element. To add a second email address I would have to first click the "Add another item" button, and then enter the email address. I am struggling to understand how to recreate this behavior in my test case. Any ideas?

The following is what I have so far:

  // Create a namecards_namecard node using the node form.
  public function testNamecardsNamecardCreate() {
    $this->drupalGet('node/add/namecards-namecard');
    // Create node to edit.
    $edit = array();
    // Enter surname
    $edit['title'] = $this->randomName(8);
    // Enter given name.
    $edit["namecards_namecard_given_name[und][0][value]"] = $this->randomName(8);
    // Enter email address.
    $edit["namecards_namecard_email[und][0][value]"] = $this->randomName(8) . '@' . $this->randomName(5) . '.com';
    // Click "add another item" for another email field.
    $this->drupalPostAJAX(NULL, array(), array('namecards_namecard_email_add_more' => 'Add another item'));
    // Enter another email address.
    $edit["namecards_namecard_email[und][1][value]"] = $this->randomName(8) . '@' . $this->randomName(5) . '.com.cn';
    $this->drupalPost('namecards/add_contact', $edit, t('Save'));
    $this->assertText(t('Namecards namecard @title has been created.', array('@title' => $edit['title'])));
    $this->assertText($edit["namecards_namecard_email[und][0][value]"]);
    $this->assertText($edit["namecards_namecard_email[und][1][value]"]);
  }

Answer 1

The problem was with the drupalPost() method. I managed to solve the problem by changing the first argument to NULL (e.g. $this->drupalPost(NULL, $edit, t('Save'));), which sets the target to the current page. Still not sure why this works instead of string denoting the path. Never-the-less it did solve the problem.