[TIP] Declarative style acceptance tests (was: Using doctest for functional tests / user stories)

[Paul Moore]

On 6 January 2014 21:50, Michael Foord <fuzzyman at voidspace.org.uk> wrote:
>>> Or is the whole idea of structuring the user stories as testable
>>> documents considered bad practice? I'm finding it very difficult to
>>> formulate good functional tests in the unittest style, but I don't
>>> want to switch to doctest if it's going to cause me problems as my
>>> development gets more complex.
>>
>> You're right, unit tests are not suited for writing acceptance tests.
>>
>
> Actually I've found unittest a perfectly good framework for writing acceptance tests. Several times.

The thing I've found frustrating when writing acceptance tests (see!
I'm trying to use the right words! :-)) is that unittest test cases
are isolated from each other. That's a positive feature when I'm
writing unit tests, but when I write an acceptance test, I feel like I
want a certain level of interdependence. Probably I'm wrong in
thinking that, but it tends to make it hard for me to get my head
round writing tests with the proper granularity.

For example:

class CreationTest(TestCase):
    def test_schema_create(self):
        "Creating the DB schema initialises the application tables"
        # Using a temporary database here
        db = myapp.DB()
        # I create the schema
        db.create_schema()
        # There should be some tables in there now...
        self.assertEqual(len(db.tables()), 4)

class AddTest(TestCase):
    def setUp(self):
        # Set up the DB for the tests - this essentially duplicates
test_schema_creation above
        self.db = myapp.DB()
        self.db.create_schema()
    def test_add_package(self):
        self.db.add_package("foo", "1.0")
        self.assertEqual(self.db.query_package("foo"), "1.0")

That duplication in setting up the DB feels wrong to me. But I can't
think of any way to refactor it. A "narrative" style of testing (which
goes step by step through the process) would fail in the same places,
but without the duplication.

Of course, I could write the narrative as a single test case:

class EnteringDataScenario1(TestCase):
    def test_create_db_and_enter_some_data(self):
        db = myapp.DB()
        db.create_schema()
        self.assertEqual(len(db.tables()), 4)
        db.add_package("foo", "1.0")
        assertEqual(self.db.query_package("foo"), "1.0")

But that starts to feel like the test is too long to be a "proper"
unittest method, particularly as the user story becomes more
elaborate.

Am I worrying too much about repetitive code in my tests?

Paul