Python unittest and exceptions: Writing custom exceptions, and catching them.

Generally in unit test, we match the responses with an expected value . But there are cases , where calling a method or passing an incorrect value (or type of value) may raise an exception . This exception might me a custom exception . Or the message or error code might me specific to the situation. So how to write test for the same.

1. Calling a method with incorrect type , raises an exception.

class MyTest(unittest.TestCase):
    def test_exception(self):
         with self.assertRaises(xmlrpclib.Fault) as cm:
            self.Proxy.setParameter('name', 1234)
            self.fail('Expected exception of type xmlrpc.Fault')

Send email with excel file as attachment

We want to send a mail which will have some content in it's body and an attachment of excel file. The excel file is not physically saved on anywhere. We have just created it, filled it and and now , we want to send it in an email.

So what we really have as an attachment is a workbook object.

Let's get started.

    from io import BytesIO
    output = BytesIO()
    attachment.save(output)
    msg = EmailMultiAlternatives(subject, "", from_email, to_email, cc=cc, bcc=bcc)
    msg.attach('my_file.xlsx', output.getvalue(), 'application/vnd.ms-excel')
    msg.attach_alternative(content, "text/html")
    try:
        msg.send()
        success = True
    except socket.gaierror:
        success = False
    return success

Nose test command line tricks

If you are using nose plugin to run your tests , there are some handy tricks that we can use while running tests.

Run test and generate a XML report:

nosetests --with-xunit test_folder --xunit-file=nosetests_test_results.xml