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Promises you can trust
{
"name": "promises",
"scripts": {
"test": "node node_modules/mocha/bin/mocha --watch --growl"
},
"devDependencies": {
"chai": "^1.10.0",
"mocha": "^2.0.1"
},
"dependencies": {
"q": "^1.1.2"
}
}
var Q = require('q');
var expect = require('chai').expect;
describe('promises', function() {
it('can be resolved', function(done) {
var promise = Q.Promise(function(resolve) {
resolve();
});
promise.then(function() {
done();
});
});
it('can pass resolution value', function(done) {
var promise = Q.Promise(function(resolve) {
resolve(6*7);
});
promise.then(function(value) {
expect(value).to.equal(42);
}).done(done);
});
it('can return the promise to mocha', function() {
var promise = Q.Promise(function(resolve) {
resolve(6*7);
});
return promise.then(function(value) {
expect(value).to.equal(42);
});
});
it('can pass values in a promise chain', function(done) {
var promise = Q.Promise(function(resolve) {
resolve(6);
});
promise.then(function(v) {
return v*7;
}).then(function(v) {
expect(v).to.equal(42);
}).done(done);
});
it('can resolve multiple promises', function(done) {
var promise = Q.Promise(function(resolve) {
resolve(['abc', 'def', 'gh']);
});
promise.then(function(array) {
return Q.all(array.map(function(v) {
return Q.Promise(function(resolve) {
resolve(v.length);
})
}));
}).then(function(lengthArray) {
expect(lengthArray).to.eql([3,3,2]);
}).done(done);
});
it('can reject a promise', function(done) {
var promise = Q.Promise(function(resolve, reject) {
reject('something went wrong');
});
promise.fail(function(error) {
expect(error).to.equal('something went wrong');
}).done(done);
});
it('treats errors as rejections', function(done) {
var promise = Q.Promise(function(resolve, reject) {
resolve(null);
});
promise.then(function(value) {
return value.length;
}).fail(function(error) {
expect(error.message).to.eql("Cannot read property 'length' of null");
}).done(done);
});
it('propagates failure to the first failure handler', function(done) {
var promise = Q.Promise(function(resolve, reject) {
resolve(null);
});
promise.then(function(value) {
return value.length; // Throws Error
}).then(function(length) {
this.test.error("never called");
}).then(function(number) {
this.test.error("never called");
}).fail(function(error) {
expect(error.message).to.eql("Cannot read property 'length' of null");
}).done(done);
});
});
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