Running Mocha + Istanbul + Babel - node.js

Question

I'm having some issues while running Istanbul with Mocha and the Babel compiler.
All my tests are running just fine, but after all the tests done it shows me this message:
No coverage information was collected, exit without writing coverage information
And it is not producing any coverage report.
The command that I am running is:
NODE_ENV=test istanbul cover _mocha -- --require babel-core/register --recursive
The project is hosted on GitHub:
https://github.com/weslleyaraujo/react-flux-puzzle/tree/feat/unit-tests-24
Any ideas what it could be?

Answer 1

Using Babel 6.x, let's say we have file test/pad.spec.js:
import pad from '../src/assets/js/helpers/pad';
import assert from 'assert';
describe('pad', () => {
it('should pad a string', () => {
assert.equal(pad('foo', 4), '0foo');
});
});
Install a bunch of crap:
$ npm install babel-istanbul babel-cli babel-preset-es2015 mocha
Create a .babelrc:
{
"presets": ["es2015"]
}
Run the tests:
$ node_modules/.bin/babel-node node_modules/.bin/babel-istanbul cover \
node_modules/.bin/_mocha -- test/pad.spec.js
pad
✓ should pad a string
1 passing (8ms)
=============================================================================
Writing coverage object [/Volumes/alien/projects/forked/react-flux-puzzle/coverage/coverage.json]
Writing coverage reports at [/Volumes/alien/projects/forked/react-flux-puzzle/coverage]
=============================================================================
=============================== Coverage summary ===============================
Statements : 100% ( 4/4 )
Branches : 66.67% ( 4/6 ), 1 ignored
Functions : 100% ( 1/1 )
Lines : 100% ( 3/3 )
================================================================================
UPDATE: I've had success using nyc (which consumes istanbul) instead of istanbul/babel-istanbul. This is somewhat less complicated. To try it:
Install stuff (you can remove babel-istanbul and babel-cli):
$ npm install babel-core babel-preset-es2015 mocha nyc
Create .babelrc as above.
Execute this:
$ node_modules/.bin/nyc --require babel-core/register node_modules/.bin/mocha \
test/pad.spec.js
...which should give you similar results. By default, it puts coverage info into .nyc-output/, and prints a nice text summary in the console.
Note: You can remove node_modules/.bin/ from any of these commands when placing the command in package.json's scripts field.

Answer 2

PS: I now recommend to use single jest instead of mocha/instanbul/nyc/chai/etc.
Solution A: Using nyc and babel-plugin-istanbul
Setup (don't forget #next for nyc):
npm install --save-dev nyc babel-plugin-istanbul babel-register
Add an env to babel config:
{
"env": {
"nyc": { "plugins": ["istanbul"] }
}
}
nyc config:
{
"reporter" : ["text", "text-summary", "lcov", "html"],
"include" : ["src/**/*.js"],
"require" : ["babel-register"],
"sourceMap" : false,
"instrument" : false,
"all" : true
}
PS: include field needs to be specified in .nycrc of in package.json, if specified in command line, coverage will not works
Running the tests:
# 1. Build
NODE_ENV=nyc babel src --out-dir lib
# 2. Coverage
nyc mocha
Solution B: No extra packages : Only the basic ones
Work has been done recently on istanbul (1.0.0-alpha.2) to support Babel generated code with sourcemaps (see #212 and this for an example).
There are 2 ways:
A. Tests written against previously transpiled code
B. Tests written against original code and transpiled all together in memory at runtime
B1. Tests that exports (previously) transpiled code
This is done in 2 steps: Firstly, build your source with babel (e.g. from ./src to ./out) and write your tests against transpiled source (export foo from "./out/foo";).
Then you will be able to run the tests using istanbul 1.0.0-alpha.2 :
istanbul cover _mocha -- ./test --compilers js:babel-register
Now if you want code coverage to follow the original code you've written (not the transpiled one), make sure to build with babel source-maps options set to both :
babel ./src --out-dir ./out --source-maps both
PS: If needed you can also do :
istanbul cover _mocha -- ./test --compilers js:babel-register \
--require babel-polyfill \
--require should \
--require sinon
B2. Tests that directly exports original code
In this case you write your tests against original source (export foo from "./src/foo";), and with no further step, you directly run istanbul 1.0.0-alpha.2 using babel-node against cli.js :
babel-node ./node_modules/istanbul/lib/cli.js cover _mocha -- ./test
PS: If needed you can also do :
babel-node ./node_modules/istanbul/lib/cli.js cover _mocha -- ./test
--require babel-polyfill \
--require should \
--require sinon

Answer 3

As of now 17.4.2016 this coverage reporting stuff is still a bit messy and with my React-project that has .jsx files and a helper file the coverage reporting script looks like this:
istanbul cover node_modules/mocha/bin/_mocha -- \
--compilers js:babel-core/register \
--require ./test/testhelper.js \
\"test/**/*#(.js|.jsx)\"
So it wouldn't be too easy the current version 0.4.3 of Istanbul doesn't work with Babel so you have to use the experimental alpha-version:
npm install istanbul#1.0.0-alpha.2 --save-dev
And then you need .istanbul.yml -file so that Istanbul recognizes the .jsx-files with these lines:
instrumentation:
root: .
extensions: ['.js', '.jsx']
And now it should work. Also as a small bonus if you want to add coverage reporting with Travis and Coveralls you should:
enable the project in https://coveralls.io
add coveralls npm i coveralls --save-dev
add this to your .travis.yml:
script:
- npm --silent test
- cat ./c
coverage/lcov.info | coveralls
And now you can put that cool badge to your README. Neato!