Speed up Dockerised tests

[JamieMason]

I'm really new to Docker so excuse me if any of the following is plain wrong, help or contributions welcome.

I think a lot of gains can be made by making better use of the Dockerfile, by moving things we wait for during the run phase into the build phase.

Notes/Ideas

• Where we currently have FROM node:4.2.4, reference a base image which sets up the shrinkpack test environment.

  In the Dockerfile for that base image;

  • Prime the npm cache by running npm cache add npm@x.x.x for every version of npm we're interested in.
  • Start some kind of caching proxy (maybe sinopia).
  • Prime the npm cache and populate the caching proxy by running npm install against the test/package.json.
• When switching npm versions, npm rebuild might be needed.
• Will likely need to change the config cache-min to be something high so npm doesn't try to refetch

See also: https://github.com/JamieMason/shrinkpack/pull/47#issuecomment-228684289 from @5id.

[5id]

I experimented with something similar where I moved the npm install of the control folder into the dockerfile, before realising that it stuffed up supporting different npm versions; so I think that's a much better way to tackle it.

You'll likely need to change the config cache-min to be something high so npm doesn't try to refetch.

Running the caching proxy in the same Dockerfile is possible, though you might find it makes it a bit messy. Potentially you could prime the local cache with an npm install to get a small bump to avoid using the proxy, but the downside of not using something like sinopia is the lack of ability to test private repos like we need for #47

[JamieMason]

Updated to include your point on cache-min, cheers! agree re: private repos too.