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0.2.30 • Public • Published


Yasmini is a light framework inspired by Jasmine. It was written for CodeGradX, an infrastructure for mechanically grading programs. Yasmini is a framework to help grading Javascript programs.

Grading programs is supported by unit testing however, rather than being strictly binary (tests pass all or fail), CodeGradX has to deliver a grade that tries to be faithful to the amount of successful tests. In order to avoid cheating, we also don't want to reveal the answers of the failed tests; we also count the number of successful expectations rather than the number of successful specifications though this number can also be taken into account.

For this personal framework (but you are free to use it), I started using Jasmine but I also wanted the same code to be used for my own tests and for grading students' programs. To achieve this, the amount of patches was too big and probably too dependent of the precise version of Jasmine so I decided to write my own framework. The name Yasmini stands for a mini-Jasmine.

Version 0.1.x only supports synchronous tests, version 0.2.x supports asynchrounous tests. However, due to the new implementation, the evaluation model of descriptions and specifications is modified and not compatible: for more details see below.


let yasmini = require('yasmini');
let describe = yasmini.describe,
    it       =,
    expect   = yasmini.expect;
describe("some program", function () {
  it("should run this", function () {
// And if you prefer full control:
let d1 = describe("some program", function () {
  let it1 = it("should run this", function () {
    let e1 = expect(2+2).toBe(4);
    let e2 = expect(e1.raisedException, {
      verbose: false
  }, { // options
        stopOnFailure: true
}, { // options
      verbose: true
}).hence(function (d1) {

As seen in the previous example and using Jasmine words, description, specification and expectation are objects that are accessible and inspectable: a reflexive feature. When built, their constructor admit an optional last parameter to set some options.

By default, there is no verbalization of the tests.


Yasmini is directly inspired by Jasmine however Yasmini is far from implementing all of Jasmine: Yasmini lacks a number of Matchers but does now (from version 0.2.x) support tests of callbacks. Yasmini is much simpler and offers other features that I found useful. So first, if you want to use Yasmini, look at Jasmine documentation on

One very important feature of Yasmini is that whenever an expectation is begun, checked, finished or a specification or a description the counters in these various instances are kept up to date. For instance the verbalizer of CodeGradX records the state of the descriptions in a file so, if the javascript process is killed from the outside (perhaps because it takes too much time), the final state of the tests can be known. Why killing from the outside ? Because programmers' code sometimes loops infinitely or waits indefinitely!


As usual. Option -g means that the installation is global.

npm install -g yasmini


The common way is to require Yasmini:

  • make the three fundamental functions (describe, it and expect) available
  • and enrich Yasmini with a verbalizer (you are free to code your own verbalizer).
let yasmini = require('yasmini');
let describe = yasmini.describe,
    it       =,
    expect   = yasmini.expect;

Yasmini also exports some classes so you may write your own hooks with



Tests are written within a Description. The first two arguments (the message and the behavior) are mandatory. The optional third argument sets some options on the Description object. All options are, well, optional, their default value is shown in this typical example below

describe("message", function () {
  // write Specifications here...
}, {
  verbose: false,
  specificationIntended: undefined
}).hence(function (description) {
  // do something with description.someField

The verbose option specifies verbosity. Its only purpose is to be inherited, by default, by specifications.

The specificationIntended if set, specifies how many specifications should be run within the description.

The describe function creates a Description instance, runs the beginHook method then runs the function given as second argument. After running that function (and all its consequences), the endHook method is run and the description will hold the following fields:

  • specifications the array of inner Specifications
  • raisedException a boolean telling if the behavior was exited with an exception
  • exception the exception if raisedException is true
  • specificationAttempted the number of attempted specifications
  • specificationSuccessful the number of successful specifications
  • pass a boolean that is true iff all specifications are passed successfully, if specificationIntended is specified then it should be equal to specificationAttempted and to specificationSuccessful.

Since inner specifications may contain asynchronous code and to be sure that the description is fulfilled, you should use the hence method. The describe function returns a kind of Promise and hence behaves as the usual then method.


Within a description are written specifications created by the it function. The first two arguments (message and behavior) are mandatory. The last one can take two forms. Or it sets options with default shown below:

let s = it("message", function () {
  // write expectations here ...
}, {
  verbose: d.verbose, // inherited
  stopOnFailure: false,
  expectationIntended: 6,
  timeout: 5*1000    // 5 seconds
// do something with some but not all s.someField
// you have to wait for the end of the specification!

Or (by compatibility with Jasmine) the last argument is a number of milliseconds that limits the duration of the expectation. This number corresponds to the timeout option and, by default, is set to 5 seconds.

The verbose option specifies verbosity. By default, it is inherited from the enclosing description. Its only purpose is to be inherited by default, by inner expectations.

The expectationIntended if set, specifies how many expectations should be run within the specification.

The stopOnFailure if true requires it to exit as soon as one expectation is not met.

The it function creates a Specification instance and stores it in the surrounding Description. Specifications are not run immediately, they are evaluated at the end of the body of the Description. This order of evaluation may puzzle you. The next example shows the order of evaluation (you may also look at the description.log that lists the internal events of the process): it prints 1, 2, 3, 4, 5.

describe("evaluation order", function () {
  let it1 = it("specification A", function () {
      let e1 = expect(3+1).toBe(4);
      // all properties of e1 are available here
  // Only static properties of it1 available here
  it("specification B", function () {
      // All properties of it1 available here
}).hence(function (description) {
   // All properties of all specifications available here.
   // The complete description.log can also be inquired.
   // The variable `it1` and `e1` are just present to name objects.
   // since it1 ==== description.specifications[0]
   //   and e1 === it1.expectations[0]

When run, the specification will invoke the beginHook method and its behavior. When the behavior terminates, the endHook method of all inner expectations are run then, the endHook method of the specification instance is run and eventually holds a number of fields:

  • expectations an array of expectations
  • description is the enclosing Description instance
  • raisedException a boolean telling if the behavior was exited with an exception
  • exception the exception if raisedException is true
  • expectationAttempted the number of attempted expectations
  • expectationSuccessful the number of successful expectations
  • pass a boolean that is true iff all expectations are passed successfully, if expectationIntended is specified then it should be equal to expectationAttempted and to expectationSuccessful.
  • endHookException if the endHook raises an exception. This is useful for hooks providers.


Expectations are created with the expect function which takes one mandatory argument and optionally some options.

// More complex example:
let e = expect(something, {
  stopOnFailure: s.stopOnFailure,
  verbose: s.verbose,
  code: "string"
}).eval().invoke(1, 2, 3).toBeTruthy().toBe(something).done();
// do something with e.someField

First the arguments are computed and given to the expect function. An Expectation instance is created and the beginHook method is run. Every matcher invocation invokes the matchHook hook. Note that the endHook is run by the enclosing specification. Among the possible options are the usual ones verbose and stopOnFailure.

The code option may be set to tailor some verbalization message. If the eval matcher is used, then code will be set with the string.

When the endHook method is run, the Expectation instance holds a number of fields:

  • specification is the enclosing Specification instance
  • index is the rank (1-based) of the expectation within the specification
  • actual is the value of the first parameter (this value may be altered by some matchers)
  • raisedException a boolean telling if the behavior was exited with an exception
  • exception the exception if raisedException is true
  • pass a boolean that is true iff the expectation was successful.
  • endHookException if the endHook raises an exception. This is useful for hooks providers.

The expectation per se does not check anything, its methods (called Matchers in Jasmine parlance) will do the work. Depending on the matcher, the first argument (say the actual) may be a string, a function or anything.

When the matchHook method is run, the Expectation instance holds a number of fields as listed above though some further matchers may alter the content of these fields.

The done method of an Expectation is optional, it only runs immediately endHook meaning that the Expectation is finished. If you do not use done then endHook will be run by the enclosing Specification. This method is so useless that it might become deprecated.


The simplest matcher is toBeTruthy which checks that actual is true according to Javascript. toBeFalsy is the opposite matcher.

Then comes toBe(expected) which checks that actual is identical to expected. Variants are toBeNull, toBeDefined, toBeUndefined and toBeNaN. A related matcher is toBeFunction.

To compare numbers you have toBeGreaterThan and toBeLessThan that implements strict comparison. Approximate comparison can be checked with toBeClose(expected, precision): the actual result should be in the vicinity of expected plus or minus 10 to the precision power. Another numeric matcher is toBeBetween(min, max) that checks that actual is between min and max (bounds included).

The toBeA(classname) checks whether actual is an instance of classname.

The toMatch(regexp) matcher converts actual to a string and checks whether the regexp acccepts it.

The toThrow matcher checks whether an exception was previously raised by the expectation. It is often used after invoke. The toNotThrow matcher checks wether no exception was previously raised by the expectation. It is often used after invoke to check that the expression was evaluated without problem whatever its final value.

The invoke matcher considers actual to be a function to invoke (possibly with some arguments); actual is reset to the obtained value.

The transform matcher is not a real matcher since it checks nothing. It applies its argument (a unary function) on the actual value and replace actual with the result. This can be used, for instance, to normalize a result.

The eval matcher considers actual to be a string which must be eval-ed. The resulting value will replace actual so you may chain this matcher with other matchers. It is possible to use toThrow after eval to check whether an exception occurred. The eval matcher can take up to two optional arguments: the context object and some options to be given to vm.runInContext.

All matchers run the matchHook hook and return the input Expectation so they may be chained. Note however that expectations are counted but not matchers so expect(...).toBe(true).toBeTruthy() only counts for one expectation.

If an expectation fails and stopOnFailure is true then a Failure (a kind of Error) is thrown with an expectation property set with the failed expectation, a matcher property with the failed matcher and an args property with the arguments of the failed matcher.

Caution: Jasmine offers some matchers that are not yet present in Yasmini: some of them are not, toContain.

Asynchronous code

You may have asynchronous tests to perform. Below is the usual synopsis:

describe("some asynchronous code", function () {
  it("should start", function (done) {
    startSomeAsynchronousCode(..., function (err, data) {
       if (err) {
       } else {
  }, 5*1000);
}).hence(function (desc) {
    // check, for instance, desc.specifications[0].pass 

Observe that the behavior of it() now takes a callback named done. You have to invoke it when the test is complete.


The file example/verbalizer.js is an example of an adjunction to Yasmini. It verbalizes in French the results of the tests. Defining beginHook and endHook on Description, Specification and Expectation does the trick.

The example/verbalize module is a simple verbalizer that displays description messages, specification messages followed by dots for successful expectations. Something like:

 (it .....)
 (another it ...!Failure!

The example/verbalize module traces every description, specification and expectation and accumulates these traces in the verbalization property of Description instances. It is up to you to display them.

The codegradx/verbalizer is a more elaborate verbalizer to be used with the CodeGradX infrastructure.

Feel free to write your own adjunctions and share them!


There are some Yasmini test files named spec/ytest*.js. They cannot be processed by Jasmine. You can run them with Yasmini as:

node spec/ytests.js

Fine points

Since hooks are your own functions they may throw exceptions. If the xHook method raises an exception then that exception will be stored in the xHookException property.


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