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Promise-based asynchronous test runner for JavaScript
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Promised-based Asynchronous Test Runner (patr) is a very simple, easy-to-use test runner that support asynchronous JavaScript testing with promises. Patr is based on the premise that testing should be as simple as creating an object with methods to perform tests. Objects can be nested to create subgroups of tests. Patr relies on the system's "assert" module for making assertions. An example test:

var assert = require("assert");
require("patr/runner").run({testMath: function(){
  assert.equal(3, Math.min(3, 5));

The suggested pattern for writing test files is to define the tests on the exports object and running the test runner if the module is the main module. This allows for direct execution of test files and easy inclusion of tests into other test groups. For example, we could define "my-math-test.js":

var assert = require("assert");
exports.testMath = function(){
  assert.equal(3, Math.min(3, 5));

if(require.main == module)

Now we can directly execute "my-math-test.js" or we could include it in another test file:

exports.mathTests = require("my-math-test");
exports.otherTests = require("other-tests");

if(require.main == module)

With these aggregate test module, each test file's tests are included in a nested object that will be tested as a subgroup of tests.

Using Promises for Asynchronous Testing

Promises make asynchronous testing very simple. You simply return a promise from your test to indicate when a test is completed. When using promise-based coding this is super simple. For example, to test the contents of file loaded asynchronously using promised-io's fs module:

var fs = require("promised-io/fs");

exports.testFile = function(){
  return fs.readFile("testfile").then(function(contents){
    assert.equal(contents.toString(), "expected contents");

Asynchronous assert module

Patr includes an "assert" module (patr/assert) that is upgraded for promise-based asynchronous code blocks. In particular, the "throws" method can be used to enforce that a code block will eventually throw (or reject) even if it happens asynchronously. For example:

var assert = require("patr/assert");
exports.testFile = function(){
  return assert.throws(function(){
    // asserts that this must throw/reject eventually
    return fs.readFile("non-existent file");

Advanced Testing

You can include additional testing options by setting flags on the test objects (that have the test functions). The test object can have the following properties:

  • iterations - The number of times to execute the test

These properties are inherited, if they are set by a parent object, than the children objects will inherit the behavior unlesss it is overriden.

These properties can also be set from the command line. This is done by including -name value arguments when starting the test module. For example:

nodules test.js -iterations 1000

Patr is part of the Persevere project, and therefore is licensed under the AFL or BSD license. The Persevere project is administered under the Dojo foundation, and all contributions require a Dojo CLA.

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