@Test
 public void emailSentToOneCustomer() throws Exception {
   underTest.sendGreetings(new BirthDate("2016-08-19"));
   MimeMessage[] emails = greenMail.getReceivedMessages();
   assertThat("Number of messages", emails.length, is(1));
   assertMessage(
       emails[0],
       new BirthdayMessage(
           "*****@*****.**",
           "*****@*****.**",
           "Alles Gute zum Geburtstag!",
           "Liebe Anastasia, Zu deinem 38. Geburtstag alles Gute ..."));
 }
 @Test
 public void emailsForCustomersWithSameBirthday() throws Exception {
   underTest.sendGreetings(new BirthDate("2016-09-23"));
   MimeMessage[] emails = greenMail.getReceivedMessages();
   assertThat("Number of messages", emails.length, is(2));
 }