test: jest 26

[ChristianMurphy]

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Description of change

Updates jest to version 26, refactors async tests to use async await.
https://jestjs.io/blog/2020/05/05/jest-26

📓 ts-jest 25 appears to work for oEQs Jest 26 needs, a version that officially supports Jest 26 is in the works kulshekhar/ts-jest#1595

[edalex-ian]

When I setup the REST Client and got the warning about this I decided to avoid it and wait - err on the side of caution. However, from looking at the ts-jest repo and milestones it looks as though it should be released in the next day or so / by end of the week.

Unfortunately the REST Client tests are not yet part of the CI, so I'll need to pull this branch and run them manually to make sure everything is still happy there too.

[edalex-ian]

ts-jest 26 is now out: https://www.npmjs.com/package/ts-jest/v/26.0.0

In the rush to get the other code done I forgot to go back to this. But I guess now we can just update both and be done with it. :)

[ChristianMurphy]

Thanks for the ping @edalex-ian, rebased and updated ts-jest

[edalex-ian]

LGTM! And the REST Client tests still run happy after the async/await updates.

Am I correct in thinking that using them in the Jest calls removes the need to do things like expect.assertions(x)?

[ChristianMurphy]

@edalex-ian it should and to be extra sure, added eslint-plugin-jest to verify this, and addressed the errors in 5aa6b9a