Dependency update: Update Mocha to version 8

[eggplantzzz]

This is a PR to update all packages (except the debugger) to version 8.

Some things to note:

• The useColors options looks like it was deprecated and therefore removed here (see breaking changes here)
• Mocha 8 is compatible with Node >= 10.12.0 and not Node 13
• The debugger package was left at version 5.x.x because it will require a bit more work to deal with deps like mocha-webpack (sorry @haltman-at).

This will be a breaking change as this will force truffle test to require the Node versions listed above and keep Truffle from supporting Node v8.

[eggplantzzz]

It seems to me that we can also remove all the Node 8 jobs from CI. This would be all the Travis stuff I believe.

[CruzMolina]

Requesting changes in core/lib/test.

Looks like this might need to wait for v6?

[eggplantzzz]

It seems like maybe we could consider it for 5.2.0.

[CruzMolina]

Planning to manually stress-test this a bit.

We probably should test the following cases:

From the terminal and within REPL contexts (console and/or develop)

1. Behavior of all tests (say 5-10) passing.
2. Behavior of a couple tests being skipped (including Contract.skip).
3. Behavior of only testing certain tests (including Contract.only).
4. Behavior when there's failing tests.

Each sets of behavior should probably be tested on Node 10, 12, & 14 LTS.

Perhaps we also want there to be a helpful error when attempting to run truffle test on Node 8.

Changes were made!

[CruzMolina]

After QA'ing a bit, everything seems to check out and I have not seen this to be an actual breaking change to end users.

It appears the mocha CLI requires Node v10.12.0 and up, but not the API.

The repl listener issue is still present in mocha v8.x for versions of Node > 12.3.0 (mochajs/mocha#4009).

[CruzMolina]

As a separate issue, it should probably be decided whether truffle is formally dropping support for Node 8.

If so, the Node 8.x GHA CI can be dropped and the Travis jobs bumped to Node 10.

As an aside, the only pkgs that need mocha bumped to provide the upgrade to truffle end-users are @truffle/core & truffle.

[haltman-at]

This mocha (the one in core, the dependency, not the dev dependency) is exposed to the user... so isn't upgrading this one a breacking change? Should this one be left as is?

[CruzMolina]

There could be some edge cases when doing customizable mocha-things (mocha-parallel tests?), but so far the core CLI functionality when running truffle test seems about the same.

I haven't checked the Library API we expose (truffle.test...), but last I checked it's undocumented and still considered experimental. 🤷‍♂️

Maybe we should dig in and outline what exactly the breaking changes are between v5.2.0 and v8.
FWIW, I don't think truffle has ever fully supported the complete features of mocha.