aggregate_tests.py fails

[VickyMerzOwn]

Description of issue or feature request:
Getting the following errors on running python3 aggregate_tests.py from within the tests/ directory.

Current behavior:

======================================================================
ERROR: test_metadata_generation (unittest.loader._FailedTest)
----------------------------------------------------------------------
ImportError: Failed to import test module: test_metadata_generation
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/unittest/loader.py", line 436, in _find_test_path
    module = self._get_module_from_name(name)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/unittest/loader.py", line 377, in _get_module_from_name
    __import__(name)
  File "/Users/usr1/Desktop/tuf/myfork/python-tuf/tests/test_metadata_generation.py", line 10, in <module>
    from tests import utils
ModuleNotFoundError: No module named 'tests'

Along with the following error:

======================================================================
ERROR: test_metafile_serialization (test_metadata_serialization.TestSerialization) (case='length 0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/usr1/Desktop/tuf/myfork/python-tuf/tests/utils.py", line 66, in wrapper
    function(test_cls, data)
  File "/Users/usr1/Desktop/tuf/myfork/python-tuf/tests/test_metadata_serialization.py", line 324, in test_metafile_serialization
    metafile = MetaFile.from_dict(copy.copy(case_dict))
  File "/Users/usr1/.local/share/virtualenvs/flask-sqlalchemy/lib/python3.8/site-packages/tuf/api/metadata.py", line 1123, in from_dict
    return cls(version, length, hashes, meta_dict)
  File "/Users/usr1/.local/share/virtualenvs/flask-sqlalchemy/lib/python3.8/site-packages/tuf/api/metadata.py", line 1088, in __init__
    self._validate_length(length)
  File "/Users/usr1/.local/share/virtualenvs/flask-sqlalchemy/lib/python3.8/site-packages/tuf/api/metadata.py", line 1056, in _validate_length
    raise ValueError(f"Length must be > 0, got {length}")
ValueError: Length must be > 0, got 0

Expected behavior:

No errors on running python3 aggregate_tests.py from within tests/

[VickyMerzOwn]

For the first failure, can I simply perform import utils directly instead of from tests import utils?

[jku]

The tests expect tuf to be installed, and will test that installed version. I'm not sure if that makes sense... but that's how it currently works. The second error implies you are running tests from one version of tuf against source from another version -- so a related error I believe.

The recommended way to develop is

• set up venv, source it
• pip install -r requirements-dev.txt -- this installs the source dir as editable so the tests find the correct source

I'm guessing tests should start working like that... but I would mind if someone figured out test imports in a way that didn't require that editable install

[jku]

I'm hesitating just closing this. It was likely a "user error" but... The failure mode is so weird if someone does not install the source dir as editable that I'm not surprised that it looks like a bug. Feels like we should be able to do better

[joshuagl]

Thanks for filing this issue!

We should improve the developer experience when testing, so that a contributor can just run the aggregate_tests.py script as the submitter did.

We need to change the script to support that:

• Do we want to run tests against the installed tuf, or the version in the scripts directory hierarchy. The latter seems the appropriate default, but there may be a case for running tests against an installed version too.
• Shouldn't the import work when running tests from the tests/ directory, are we doing the import wrong and expecting the tests to be installed?