Improved test assertion method

[rennerocha]

When a test fails, there are no clear indication of the input strings used for the test. This makes identifying which test case is failing very difficult.

Current:

    def test_parsing(example: Example):
        parsed = Price.fromstring(example.price_raw, example.currency_raw)
>       assert parsed == example
E       AssertionError: assert Price(amount=None, currency='EUR') == Example(amount=None, currency=None)

After this PR:

    def test_parsing(example: Example):
        parsed = Price.fromstring(example.price_raw, example.currency_raw)
>       assert parsed == example, f"Failed scenario: price={example.price_raw}, currency_hint={example.currency_raw}"
E       AssertionError: Failed scenario: price=SOMETHING EUROPE SOMETHING, currency_hint=None
E       assert Price(amount=None, currency='EUR') == Example(amount=None, currency=None)

[codecov]

Codecov Report

Merging #13 into master will not change coverage.
The diff coverage is n/a.

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[kmike]

I wonder if it would be better to use pytest ids for this - see https://docs.pytest.org/en/latest/example/parametrize.html#different-options-for-test-ids. We can use Example as an id; this would also allow to have more readable test names for tests which are passing.

[rennerocha]

The representation of Example is useless. As it inherits from Price, its string representation doesn't contains the input arguments to fromstring method. IMO this is the most important information that is missing when our tests fails.

This is what we get from Example repr:

ipdb> repr(value)                                                                                                                                                           
"Example(amount=Decimal('12.99'), currency='US$')"

As you can see, it shows nothing about the the input US$:12.99.

But these are the information that we really need when reading the tests fails:

ipdb> value.currency_raw, value.price_raw                                                                                                                                   
(None, 'US$:12.99')

We could create an id based on the raw values. It is better than the actual error, but as we have limitations over the characters that can be user as an id (considering that the inputs has spaces and special characters), it won't contain more detailed information about the inputs.

Another option I can see is to define __repr__ of Example class, so it returns all values provided.

However, I believe that the only values that really matter when we see an error are the ones passed to .fromstring method.

[kmike]

ok, fair enough, thanks for the explanation @rennerocha!