ElementUI tests throw ReferenceError: _Message is not defined - vue.js

Question

Bug report on ElementUI
I am using On-demand loading of ElementUI components. I've followed the instructions correctly and it works just fine when running the app.
The problem arises when I try to test with Jest and Vue test utils. None of the components I am importing seem to be found, so I get this error when running my tests:
ReferenceError: _Message is not defined
I get the same error for any of the other components, that my test touches.
On the bug report I mentioned above, I am being suggested that my babel configuration is not being applied in my testing environment? Or its something about my Jest configuration. I've tried various things to fix this:
Doing a manual mocks
Spying on the component
Importing the whole ElementUI package inside my test
Updating Jest configuration
Nothing seems to work and I have no idea what is wrong...
bebel.config.js
module.exports = {
presets: [
'#vue/app',
],
plugins: [
[
'component',
{
libraryName: 'element-ui',
styleLibraryName: 'theme-chalk',
},
],
],
};
jest.config.js
module.exports = {
// roots: ['<rootDir>/src/', '<rootDir>/tests/'],
moduleFileExtensions: [
'js',
'jsx',
'json',
'vue',
],
transform: {
'^.+\\.vue$': 'vue-jest',
'.+\\.(css|styl|less|sass|scss|svg|png|jpg|ttf|woff|woff2)$': 'jest-transform-stub',
'^.+\\.jsx?$': 'babel-jest',
},
transformIgnorePatterns: [
'/node_modules/(?!element-ui)',
],
moduleNameMapper: {
'^#/(.*)$': '<rootDir>/src/$1',
'^.+\\.(css|styl|less|sass|scss|png|jpg|ttf|woff|woff2)$': 'jest-transform-stub',
},
snapshotSerializers: [
'jest-serializer-vue',
],
testMatch: [
'**/tests/**/*.spec.(js|jsx|ts|tsx)|**/__tests__/*.(js|jsx|ts|tsx)',
],
testURL: 'http://localhost/',
watchPlugins: [
'jest-watch-typeahead/filename',
'jest-watch-typeahead/testname',
],
collectCoverage: true,
coverageReporters: ['lcov', 'text-summary'],
};

Answer 1

I have a couple of suggestions for you here:
change this in jest.config.js
module.exports = {
moduleFileExtensions: [
'js',
'jsx',
'json',
'vue',
],
transform: {
'^.+\\.vue$': 'vue-jest',
'.+\\.(css|styl|less|sass|scss|svg|png|jpg|ttf|woff|woff2)$': 'jest-transform-stub',
'^.+\\.(js|jsx)?$': 'babel-jest'
},
moduleNameMapper: {
'^#/(.*)$': '<rootDir>/src/$1',
'^.+\\.(css|styl|less|sass|scss|png|jpg|ttf|woff|woff2)$': 'jest-transform-stub',
},
snapshotSerializers: [
'jest-serializer-vue',
],
testMatch: [
'**/tests/**/*.spec.(js|jsx|ts|tsx)|**/__tests__/*.(js|jsx|ts|tsx)',
],
testURL: 'http://localhost/',
watchPlugins: [
'jest-watch-typeahead/filename',
'jest-watch-typeahead/testname',
],
collectCoverage: true,
coverageReporters: ['lcov', 'text-summary'],
};
and this in babel.config.js
module.exports = {
presets: [
'#vue/app',
],
plugins: [
[
'component',
{
libraryName: 'element-ui',
styleLibraryName: 'theme-chalk',
},
],
],
"env": { "test": { "plugins": ["transform-es2015-modules-commonjs", "dynamic-import-node"] } }
};
Also I believe #babel/plugin-transform-modules-commonjs is needed in yarn.
Let me know if this works.