TST: Add input validation tests

[sandhujasmine]

Fixes GH 1418

Issue status

[llllllllll]

We should move this out of the context manager. As a general rule context invariant code should not be placed in the context manager when possible because then readers need to know if the context manager affects the code in any way. In this particular case, if symbol raises a TypeError then this test will pass when it shouldn't

[sandhujasmine]

Indeed - thanks @llllllllll
Fixed and tested.

[llllllllll]

How do you feel about testing the contents of the error strings?
something like:

with pytest.raises(Error) as e:
    ...
assert '...' in str(e.value)
assert str(e.value) == '...'

We might want to test that the error message includes the correct column or incorrect value.

[llllllllll]

Can we use triple quoted strings for docstrings. It took me a second to realize this was the docstring.

[sandhujasmine]

How do you feel about testing the contents of the error strings?

I feel good about it - I had added but wasn't sure if it was overkill. It's easy to add so I'll update.

Can we use triple quoted strings for docstrings

Yes, will fix.

[sandhujasmine]

How do you feel about testing the contents of the error strings?
something like:

with pytest.raises(Error) as e:
   ...

@llllllllll

Instead of doing an exact match would it suffice to check substring? This will keep it concise and not require string formatting. I don't think exact match buys us much more once we've validated the correct exception was raised.

with pytest.raises(TypeError) as excinfo:
    join(a, b, 'x')

assert 'Schemata of joining columns do not match,' in str(excinfo.value)

The exact message for this exception is:
'Schemata of joining columns do not match,' ' no promotion found for %s=%s and %s=%s' % ( on_left[n], left_types[n], on_right[n], right_types[n], )

[llllllllll]

that is fine, we might want to just check that the expected column names appear in the string

[llllllllll]

Thank you for the test cases!

[sandhujasmine]

@kwmsmith, @llllllllll

I was thinking to move exception tests for objects defined in collections module from test_interactive.py to test_collections.py, so moving:
test_sample_failures(), test_distinct_failures(), test_merge_failure()

I added the last two here but seems like the general convention is for tests for a module to be in associated test_.py

What do you think?

[llllllllll]

Moving the tests sounds good. Keeping tests organized makes it easier for developers to find the place to add new tests which encourages better testing.

[kwmsmith]

I was thinking to move exception tests for objects defined in collections module from test_interactive.py to test_collections.py

👍

[llllllllll]

Thank you for these tests and cleaning up the existing ones!