I am struggling trying to understand how to write tests in Flask.
I've inherited an app that already has a bunch of tests that hit routes like /login and test that the response is what's expected.
I have a substantially more complicated situation. I need to test a route/method that depending on the circumstances, hits an external api, figures out whether a path exists in the container the app itself is running in, starts a process that takes 10+ minutes to run on a different machine -- all manner of things. So I can't just hit the route and see if I got what I wanted; I need mocking and patching to mimic the effects of various external world states.
Right now I have a route defined like so in brain_db/views.py:
@app.route('/label_view/<int:scan_number>')
@login_required
def label_view(scan_number):
<so much complicated logic>
The first route defined in that same file, brain_db/views.py, is
@app.route('/surface_test')
def surface_test():
<some code>
Here is a simplified version of the file that's throwing the error:
import unittest
from mock import MagicMock, patch
from flask_brain_db.test_helpers import set_up, tear_down
from flask_brain_db.brain_db.models import Scan
from brain_db.views import label_view
class BrainDBTest(unittest.TestCase):
def setUp(self):
app, db = set_up()
scan = Scan(1, '000001', '000001_MR1', 'scan.nii.gz', scan_number=1)
db.session.add(scan)
scan = Scan.query.filter(Scan.scan_number == 1).first()
db.session.commit()
def tearDown(self):
tear_down()
def mock_volume_views_setup(self)
scan = Scan.query.filter(Scan.scan_number == 1).first()
container_file_path = '/path/to/file/in/container'
return scan, container_file_path
def mock_os_path_exists(self, arg):
return True
@patch('brain_db_helpers.volume_views_setup', mock_volume_views_setup)
@patch('os.path.exists', mock_os_path_exists)
def test_label_view(self):
rv = label_view(1)
assert(True) # I'll actually write tests when I figure out that I can!
print rv
Here is the error:
======================================================================
ERROR: brain_db.tests.test (unittest.loader.ModuleImportFailure)
----------------------------------------------------------------------
ImportError: Failed to import test module: brain_db.tests.test
Traceback (most recent call last):
File "/usr/local/lib/python2.7/unittest/loader.py", line 254, in _find_tests
module = self._get_module_from_name(name)
File "/usr/local/lib/python2.7/unittest/loader.py", line 232, in _get_module_from_name
__import__(name)
File "/usr/src/app/flask_brain_db/brain_db/tests/test.py", line 7, in <module>
from brain_db.views import label_view
File "/usr/src/app/flask_brain_db/brain_db/views.py", line 36, in <module>
@app.route('/surface_test')
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1250, in decorator
self.add_url_rule(rule, endpoint, f, **options)
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 66, in wrapper_func
return f(self, *args, **kwargs)
File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1221, in add_url_rule
'existing endpoint function: %s' % endpoint)
AssertionError: View function mapping is overwriting an existing endpoint function: surface_test
What I have done to try to solve my problem: I've read a bunch of the posts on SO that quote that same AssertionError. E.g. 1, 2. I can see that the general shape of the problem is that my routes have already been defined, and
from brain_db.views import label_view
is executing the views module again, thus redefining the routes, so I get an error thrown.
What I don't understand is how exactly I should avoid this. I need to be able to import a method into another file to be able to test it. Are all the routes supposed to be wrapped in if __name__ == main? I am brand new to Flask development and haven't yet seen example code where this is the case; I'm dubious that this is the correct solution; it's just the only thing that's offered when you try to search for preventing code from being executed on import.
The way I'm running my tests right now is via the file manage.py in the top level of my application. It contains the following method:
@manager.command
def test():
"""Runs the tests without coverage"""
tests = unittest.TestLoader().discover(start_dir='.', pattern='test*.py')
res = unittest.TextTestRunner(verbosity=2).run(tests)
sys.exit(not res.wasSuccessful())
I run python manage.py test at the command line.
It also might be relevant that while I've put the test that's failing in a submodule within brain_db, several tests run before it that hit routes defined in the app and test for the expected result. However, commenting out those tests has no effect on the way my test is failing.
Finally, I was initially getting an error at the line from flask_brain_db.brain_db.models import Scan:
ERROR: brain_db.tests.test (unittest.loader.ModuleImportFailure)
----------------------------------------------------------------------
ImportError: Failed to import test module: brain_db.tests.test
Traceback (most recent call last):
File "/usr/local/lib/python2.7/unittest/loader.py", line 254, in _find_tests
module = self._get_module_from_name(name)
File "/usr/local/lib/python2.7/unittest/loader.py", line 232, in _get_module_from_name
__import__(name)
File "/usr/src/app/flask_brain_db/brain_db/tests/test.py", line 5, in <module>
from flask_brain_db.brain_db.models import Scan
File "/usr/src/app/flask_brain_db/brain_db/models.py", line 6, in <module>
class Scan(db.Model):
File "/usr/local/lib/python2.7/site-packages/flask_sqlalchemy/model.py", line 67, in __init__
super(NameMetaMixin, cls).__init__(name, bases, d)
File "/usr/local/lib/python2.7/site-packages/flask_sqlalchemy/model.py", line 121, in __init__
super(BindMetaMixin, cls).__init__(name, bases, d)
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/ext/declarative/api.py", line 65, in __init__
_as_declarative(cls, classname, cls.__dict__)
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 116, in _as_declarative
_MapperConfig.setup_mapping(cls, classname, dict_)
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 144, in setup_mapping
cfg_cls(cls_, classname, dict_)
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 172, in __init__
self._setup_table()
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 465, in _setup_table
**table_kw)
File "/usr/local/lib/python2.7/site-packages/flask_sqlalchemy/model.py", line 90, in __table_cls__
return sa.Table(*args, **kwargs)
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/sql/schema.py", line 439, in __new__
"existing Table object." % key)
InvalidRequestError: Table 'scan' is already defined for this MetaData instance. Specify 'extend_existing=True' to redefine options and columns on an existing Table object.
I made it go away by including
__table_args__ = {'extend_existing': True}
In the model definition, but I don't know if I should have done that and I suspect I was just postponing the same problem I have now. It seems like the fundamental problem is that I don't know how to write tests without redefining a bunch of things that have been already been defined.
What is the correct way to approach this? Please let me know if I need to provide any other information.
