Breaking change: Remove test facilities for downstream users

[jakobnissen]

Right now, TranscodingStreams.jl (TS) provides test facilities in src/testtools.jl to be used by downstream packages. An unfortunate consequence of this is that TS now depends on Test and Random, for no good reason. (See #100)

This change makes these dependencies test-only dependencies. Not that this is a breaking change, because dependencies on TS right now may use TS's test facilities in their own tests. However, this change will only break test code, not TS usage "in the wild".

[devmotion]

I'm wondering about what's the best way to do in a similar situation in some other packages. There we want to provide tests for an interface since downstream packages really should have access to a standardized test suite.

In your opinion, should downstream packages such as CodecLz4 construct the path to the test/testutils.jl file in their tests and include it manually (e.g., in https://github.com/JuliaIO/CodecLz4.jl/blob/092191810862b4b94fe44a939e39e1095013013f/test/frame_compression.jl#L2)? That seems a bit inconvenient for downstream packages. Maybe the package should provide some functionality for making it easier to include this file? But then downstream packages would still need to ensure that all required dependencies are installed.

Maybe an extension with test utilities could be an alternative (with a weak dependency on Test - or maybe that's not possible?)? Or a subpackage?

I'm mainly curious about your general opinions, I don't want to change this PR since I don't work with TranscodingStreams 🙂

[ViralBShah]

We should merge this. Any reason not to at this point?

[devmotion]

FYI in AbstractFFTs we made Test a weak dependency for now, but it was not completely clear if a separate subpackage would be the better option. Hiding the test utilities in /test seemed not a good alternative for us since it would mean that downstream packages - which are supposed to use the test utilities - depend on the internal file structure of AbstractFFTs.

[ViralBShah]

Pinging @StefanKarpinski since he also opened #100.

[nhz2]

This was fixed by #152