update jest to ^25

[ItsANameToo]

What problem does this feature solve?

Jest 25 was released a few days ago: https://jestjs.io/blog/2020/01/21/jest-25 . It would be appreciated if the vue-cli-plugin-jest would be updated to use that version instead of ^24.9.0

What does the proposed API look like?

Update the jest dependency to its latest version

[LinusBorg]

That will happen in the next major as it's a breaking change

[DRoet]

didn't @vue/cli 4.0 already make a non breaking transition possible by pulling in jsdom v15?

[LinusBorg]

If that's really the only breaking change, then yes. The release announcement wasn't too clear about this.

[sodatea]

I thought so, but it turns out not the case. The jsdom-v15 thing only makes the transition easier but there are still breaking changes.

1. Packages like ts-jest rely on hard-coded Jest version and it's not under our control.
2. Seems Jest 25 breaks vue-jest test coverage Vue SFCs not included in coverage reports vue-jest#217

[JordyLangen]

In our current project we are running:

"@vue/cli-plugin-unit-jest": "4.3.1",
"jest": "25.5.2",
"ts-jest": "25.3.1",
"vue-jest": "3.0.5",

Fixing the jest version like this:

"resolutions": {
    "jest": "25.5.2"
  },

Which does seem to work for us, which would also imply that jest 25.* is not a breaking change?
Both test execution and code coverage is working.

[LinusBorg]

Which does seem to work for us, which would also imply that jest 25.* is not a breaking change?

It's merely implies that your codebase doesn't use any part of jest that has a breaking change, and thus isn't affected.

[sodatea]

Think about this use case:

package.json:

{
  "@vue/cli-plugin-unit-jest": "^4.1.0",
  "ts-jest": "^24.0.0"
}

ts-jest has hard-coded the allowed jest version range. So if we silently updated the underlying jest version to v25, it will throw. That will break the user's project.

[just-boris]

The Jest 26 is out: https://jestjs.io/blog/2020/05/05/jest-26

Among other important changes, it has an upgraded JSOM.

In my Vue app I use web-components, which do not work in JSDOM versions < 16. As an intermediate solution I am using jest-environment-jsdom-sixteen, but it would be great to have this integration built-in

[ihorbond]

Agreed please upgrade to Jest 26 so we can test web components

[gregveres]

I upgraded jest to v26 with this in my package.json file. (using Yarn)

  "resolutions": {
    "jest": "^26.6.3",
    "ts-jest": "^26.4.4",
    "babel-jest": "^26.6.3"
  }

Now I can use jset v26 while waiting for @vue/cli-plugin-unit-jest to be upgraded.