Issues with coverage and rewire

[tandros-div]

🐛 Bug Report

Hi,
I have a public repo that doesn't produce coverage for file scraper.test.js. File is found in tests directory. I do have another test file that doesn't have any issue.

However, the problematic file is using rewire npm module, and I have seen some issues with it lately. I did try to completely remove it, but the problem still persists.

To Reproduce

In folder crawler
Run:
jest --coverage --bail --findRelatedTests ./__tests__/scraper.test.js
or:
jest --coverage

Expected behavior

I expect to see coverage report for scraper.js.
Tests run successfully but I there is no coverage data.

Link to repl or repo

Repo - develop branch

envinfo

System:
OS: Linux 5.2 Fedora 30 (Workstation Edition) 30 (Workstation Edition)
CPU: (4) x64 Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz
Binaries:
Node: 12.8.1 - /usr/bin/node
npm: 6.11.2 - ~/.npm-packages/bin/npm
npmPackages:
jest: ^24.9.0 => 24.9.0

[thymikee]

Please provide some instructions in the repro on what's the issue and how to achieve it

[An-dz]

Just try loading a module with rewire instead of require and jest will not calculate coverage of this file.

[JNBourrat]

@tandros-div Hi! I'm running into the same issue unfortunately: jest --coverage does not seem to take into account my rewired modules. Did you find a way to report you actual test coverage?

[SimenB]

I doubt we'll add support for rewire (jest has builtin support for mocking modules via jest.mock and jest.doMock), but if anybody wanna send a PR that's of course welcome

[An-dz]

@JNBourrat I decided to go with AVA. I ended up really liking the way it works and its syntax, including that not writing an assert fails the test.

[JNBourrat]

@An-dz Thanks, I'll be sure to take a look at it.

For my end I ended up using babel-plugin-rewire instead of rewire itself. I was able to use __get__ and __set__ to mock the tested module's private functions and not rewire the whole module.

[An-dz]

@JNBourrat I thought about using babel-rewire but it has many dependencies and I wanted to keep my project slim.

@SimenB nyc/istanbul had a similar bug I helped to track down, whenever you guy wish to try to fix this these are the issues:
istanbuljs/nyc#1169
istanbuljs/nyc#1029

[cqcmdwym]

Found a temp solution: https://www.grzegorowski.com/jest-tests-with-rewire-plugin
We can use babel-jest and babel-plugin-rewire

[ryancabanas]

Found a temp solution: https://www.grzegorowski.com/jest-tests-with-rewire-plugin We can use babel-jest and babel-plugin-rewire

@cqcmdwym I followed the simple instructions that you linked, but I can't get babel-plugin-rewire to work. I keep getting the message TypeError: Cannot read property '__Rewire__' of undefined when I try to use it. :( You didn't happen to run into any additional configuration steps that needed to be done to get this to work with Jest unit tests, did you? Thanks so much for the help!

[cqcmdwym]

Found a temp solution: https://www.grzegorowski.com/jest-tests-with-rewire-plugin We can use babel-jest and babel-plugin-rewire

@cqcmdwym I followed the simple instructions that you linked, but I can't get babel-plugin-rewire to work. I keep getting the message TypeError: Cannot read property '__Rewire__' of undefined when I try to use it. :( You didn't happen to run into any additional configuration steps that needed to be done to get this to work with Jest unit tests, did you? Thanks so much for the help!

Looks like you haven't configed babel in babel config file?

[SergioSuarezGil]

Hi guys, i'm trying to use babel-jest and babel-plugin-rewire

but i have these errors (a lot of them)

Property property of OptionalMemberExpression expected node to be of a type ["Identifier"] but instead got "CallExpression"

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