How to mock Transport.send() method in this method using MockitoJUnitRunner? - mockito

Question

I want to write the testcase for the given method. But there exist a static Transport.sendEmail method.
How can I mock this method using MockitoJunitRunner.
public void sendEmail(final String message, final String contentType) {
final Session session = Session.getDefaultInstance(PROPERTIES, null);
final Multipart mpart = new MimeMultipart();
final MimeBodyPart body = new MimeBodyPart();
try {
body.setContent(message, contentType);
mpart.addBodyPart(body);
Transport.send(createMessage(session, mpart));
LOGGER.info("Email Notification Sent Successfully");
} catch (MessagingException | UnsupportedEncodingException e) {
LOGGER.error("Was not able to send mail", e);
}

Answer 1

So:
Transport.send(createMessage(session, mpart));
that static call means: you can't "control" it using Mockito. Plain and simple. If that call just "passes" in your unit test environment, well, then you can test it, but not verify that the call really took place. Worse, if that call throws some exception in the unit test setup, then heck, what could you do?
Options:
turn to PowerMock(ito) or JMockit, as they allow you to gain control
recommended: improve your design to be easy-to-test
That last idea comes in various flavors:
For example, you could create a minimal interface EmailSenderService that offers a void send(Message whatever) method. Next: you create one implementation of that interface that simply invokes that static method. Now your code that actually has to send that message ... simply gets passed in an instance of EmailSenderService. And within your unit tests, you can now #Mock that interface, and you gain control over it.
Alternatively, you simply deprecate that static method (maybe the whole class), and you design a new "real" EmailSenderService that doesn't rely on static methods.