Transfer tests from topo about param

[ceball]

Made a start by copying one test file from topographica, but it's just a placeholder for now.

[ceball]

Note that topographica's testing also generates a coverage report.

[ceball]

Seems like coveralls.io might be ok for showing coverage (https://coveralls.io/r/ioam/param; need to tweak which files it considers).

[jbednar]

Cool. I can't quite parse the output; it seems to consider the tests to have good coverage (of themselves?)

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[jlstevens]

I've moved all the relevant topographica unit tests over to param. I also ported the appropriate doctests in topographica to suitable unit tests. If there is anything else here you want ported, please tell me.

The only test that I can see that has anything param specific is this one as it tests param.Filename. Unfortunately, it is mixed with Topographica specific stuff (namely save_snapshot and load_snapshot).

I haven't touched the paramtk tests but that is an issue for a different repository...

[jbednar]

Thanks so much for doing that! What's the motivation for porting doctests to unit tests?

[jlstevens]

Really, it is just a matter of preference!

I don't mind doctests inside actual docstrings but I don't like having files containing doctests when we could just have unit tests instead. We have far more unit tests than doctest files so I think we should aim for unit tests + doctests in docstrings.