Use pytest instead of unittest

[CasperWA]

Closes #270

This PR moves the tests completely over to the pytest way of doing things, instead of unittest.
There is only a single place left that still uses unittest, specifically the unittest.mock.patch feature.
This may be converted to pytest's monkeypatch as well, but for now I didn't see the reason.

The conversion makes much of the testing redundancy superfluous, due to the usage of the pytest fixtures and parametrizations.
There is potentially still room for further simplifications, when testing the entry endpoints, however then the file structure and concept division may fail (if, e.g., similar tests for /references and /structures are combined using parametrization, it may be more obfuscating than actuallly helpful and clear).

The client_factory() is technically not necessary. However, since I found it useful in aiida-optimade for a middleware test that redirects the documentation URLs between the versioned URLs, I have left it in here, if similar tests involving the versioned base URLs become relevant.

[codecov]

Codecov Report

Merging #390 into master will increase coverage by 0.73%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #390      +/-   ##
==========================================
+ Coverage   89.62%   90.36%   +0.73%     
==========================================
  Files          55       55              
  Lines        2459     2459              
==========================================
+ Hits         2204     2222      +18     
+ Misses        255      237      -18     

Flag	Coverage Δ
#unittests	90.36% <100.00%> (+0.73%)	⬆️

Impacted Files	Coverage Δ
optimade/server/entry_collections/mongo.py	95.91% <100.00%> (+9.18%)	⬆️
optimade/server/routers/utils.py	90.34% <0.00%> (-0.69%)	⬇️
optimade/server/main.py	95.74% <0.00%> (+10.63%)	⬆️
optimade/server/main_index.py	95.74% <0.00%> (+10.63%)	⬆️

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[ml-evs]

Looks great @CasperWA, just a couple of minor things that don't stop me accepting

[ml-evs]

Minor stuff, looks like the checks aren't running atm anyway... happy to accept shortly

[ml-evs]

Great work as always, cheers @CasperWA

[CasperWA]

I needed to try and push something else, in order to try and get the pre-commit test running correctly.
So I have updated all default installations of Python 3.7 in the CI to Python 3.8.
Feel free to re-approve when tests succeed @ml-evs :)

[CasperWA]

Hmm. I'm not touching any files in this PR that would influence the OpenAPI generation. So I am very confused by the sudden failure of the OpenAPI diff check in pre-commit CI.

Also, I cannot reproduce the error locally.

[ml-evs]

Also, I cannot reproduce the error locally.

I can reproduce it in a fresh Python 3.8 env, but can't in the 3.7 env I use for development. Will see if there's a diff between the packages getting installed.

[ml-evs]

It's the upgrade to pydantic 1.6.1 that's causing the diff, now to figure out why pre-commit is using that version...

[ml-evs]

Here's the change that's causing it too, from https://github.com/samuelcolvin/pydantic/blob/master/HISTORY.md

• Remove extra allOf from schema for fields with Union and custom Field, The validator should check for meta->schema #1209 by @mostaphaRoudsari

[ml-evs]

👍

[CasperWA]

Here's the change that's causing it too, from https://github.com/samuelcolvin/pydantic/blob/master/HISTORY.md

• Remove extra allOf from schema for fields with Union and custom Field, The validator should check for meta->schema #1209 by @mostaphaRoudsari

This change is actually really good. It cleans up the OpenAPI schema 👍
But let's wait until dependabot complains to treat this - or force an update from dependabot.
In any case, your addition of the requirements*.txt files is appropriate.

[ml-evs]

Here's the change that's causing it too, from https://github.com/samuelcolvin/pydantic/blob/master/HISTORY.md

• Remove extra allOf from schema for fields with Union and custom Field, The validator should check for meta->schema #1209 by @mostaphaRoudsari

This change is actually really good. It cleans up the OpenAPI schema +1
But let's wait until dependabot complains to treat this - or force an update from dependabot.
In any case, your addition of the requirements*.txt files is appropriate.

Yeah it looks good, we should remember to upgrade pydantic before we next merge back into the spec repo (if that is before dependabot triggers).