Mocking file system contents not working with gulp.src - node.js

Question

I'm trying to use mock-fs to mock up file system contents to test gulp tasks. Unfortunately, gulp.src doesn't seem to play well with mock-fs. Specifically, I get ENOENT errors:
Message:
ENOENT, lstat '/vagrant/study-node-heroku/instances/development/app.json'
Details:
errno: -2
code: ENOENT
path: /vagrant/study-node-heroku/instances/development/app.json
domainEmitter: [object Object]
domain: [object Object]
domainThrown: false
Stack:
Error: ENOENT, lstat '/vagrant/study-node-heroku/instances/development/app.json'
at Error (native)
Other parts of my code and test code access the mock-fs-created files just fine.
What am I doing wrong? I suspect that the problem is related to gulp's usage of vinyl.
Here is the function under test:
var herokuTarball = function(options, done) {
var instance = options.instance || 'development';
var tarballName = options.tarballName || instance
var tarballPath = path.join(config.temp, tarballName + '.tar.gz');
var files = path.join(config.instances, instance, '**/*');
yassert.file(path.join(config.instances, instance, 'app.json'));
async.waterfall([
function(cb) {
del([tarballPath], cb);
},
function(err, cb) {
gulp.src(files)
.pipe(tar(tarballName + '.tar'))
.pipe(gzip())
.pipe(gulp.dest(config.temp))
.pipe(gcallback(cb));
}
], function(err, result) {
if (err) return err;
return done(err, tarballPath);
});
}
And here is the test snippet:
describe('gulp heroku:tarball', function() {
after('something', function() {
mock.restore();
});
before('something', function() {
mock({
'instances/development': {
'app.json': 'test content'
}
});
});
it('creates a tarball', function(done) {
var options = {}
heroku.herokuTarball(options, function(err, result) {
expect(result).to.be.a('string');
yassert.file(result);
done();
});
});
});
Notice that the yassert (yeoman-assert) calls pass fine -- the file is there. If I take the function with the gulp.src call out of the async waterfall, the error goes away (and the test fails of course).
Issue posted at https://github.com/tschaub/mock-fs/issues/44

Answer 1

You are not doing anything wrong, mock-fs README states:
Note mock-fs is not compatible with graceful-fs#3.x but works with graceful-fs#4.x.
Looking at the dependencies of gulp we get:
$ npm info gulp devDependencies.graceful-fs
^3.0.0
Hence, gulp is still dependent on graceful-fs#3.x, therefore mock-fs will not work.
YMMV, but maybe vinyl-fs-mock is an alternative?