Restore testing

[astrojuanlu]

Is there anything similar to https://pypi.org/project/pytest-cookies/ but for Copier?

[astrojuanlu]

To test #8 I did the following manually:

* make a test project using `copier template test`

* `validate-pyproject test/pyproject.toml`

Would it be valuable to have some sort of automated test that did something like this? More generally, should there be something to ensure that the baked test project adheres to the linting standards that it comes with. e.g. maybe by running the pre-commit hooks against that project? (If you'd like to do validate-pyproject as a pre-commit hook, that's possible also.)

(Posted by @AntonyMilneQB in gh-9)

[astrojuanlu]

There's a couple of pytest fixtures now we can use: pytest-copier and pytest-copie (not a typo, see noirbizarre/pytest-copier#10)

pytest-copie seems to be more backwards compatible with pytest-cookie.