Tests failing with `No coverage available for <vue files only>`

Originally posted at vuejs-templates/webpack; steps to reproduce the issue are in that post.

Tests were working on Saturday; they started failing last night (PST). JavaScript-only Jest tests without Vue components pass with coverage enabled. Vue tests pass if coverage is disabled.

Note: The setup for this is defect to simply use the vue-cli to install the webpack template and run npm run test. I’m using Windows 10.

[ccamarat]

I was able to throw a couple hours at this one today. I’ve got a successful (if limited) workaround and was able to determine that the issue was introduced with Jest v22.0.0. I also have some info that may help someone track this down or resolve.

Work Around Place the Jest configuration directly inside package.json following the vue test utils jest-example

Troubleshooting Activities

• Tried the Vue Test Utils Jest Example: Issue not present
• Compared the Vue Webpack Template looking for differences
  1. Copied the config file from the template to the test utils and updated unit script to use it - issue not present
  2. With above config file in place, updated Jest from ^21.1.0 to Jest 22.0.0 - issue appears (experimented with several explicit 22.* versions; issue was introduced in 22.0.0, which unfortunately has a long changelist ).
  3. Backed out config file change from #i (using example’s package.json config) - issue not present

I futzed around with the config file for a while. For a bit I was hopeful that the path.resolve() was somehow involved because removing it caused the problem to disappear. I’m pretty sure this was a red herring (but not completely sure); the coverage report was simply “All files: Unknown”.

The last piece of information while reviewing the coverage report itself. As @BeauAgst pointed out, the coverage report lists the tested Vue files twice, while the untested Vue files are only listed once. I’m not sure how many core devs use Windows so I’ll post a picture: I find it interesting that a file with no branches would report 50% coverage (while it’s peer shows 100% covered with 0% overall).

[ccamarat]

Thanks. I was away from jest for a bit and lost track of this. I tried it again the other day and did not notice the duplicated report anymore. Thanks again!