Is there a way to add a Jasmine matcher to the whole environment

Question

There are plenty of documents that show how to add a matcher to a Jasmine spec (here, for example).

Has anyone found a way to add matchers to the whole environment; I'm wanting to create a set of useful matchers to be called by any and all tests, without copypasta all over my specs.

Currently working to reverse engineer the source, but would prefer a tried and true method, if one exists.

score 48 · Accepted Answer · answered Aug 13 '12 at 20:54

48

Sure, you just call beforeEach() without any spec scoping at all, and add matchers there.

This would globally add a toBeOfType matcher.

beforeEach(function() {
  var matchers = {
    toBeOfType: function(typeString) {
      return typeof this.actual == typeString;
    }
  };

  this.addMatchers(matchers);
});

describe('Thing', function() {
  // matchers available here.
});

I've made a file named spec_helper.js full of things like custom matchers that I just need to load onto the page before I run the rest of the spec suite.

answered Aug 13 '12 at 20:54

Alex Wayne

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1

I also found a nice example here: http://tobyho.com/2012/01/30/write-a-jasmine-matcher/ – Dancrumb Aug 13 '12 at 21:13
I tried link shared by Dancrumb, ideally its neat and clean approach however it didn't work so I adopted Alex approach. – joy May 07 '14 at 15:42
2

Here's one for jasmine 2.0+ ````javascript beforeEach(function(){ jasmine.addMatchers({ toEqualData: function() { return { compare: function(actual, expected) { return { pass: angular.equals(actual, expected) } } } } }); }); ```` – mikker Dec 04 '14 at 11:56
1

@mikker You should edit the answer or post your own rather than leaving that in a comment. http://stackoverflow.com/help/editing – Lexi Apr 22 '15 at 16:44
@Dancrumb, there is a problem with defining matcher like that. It adds to `jasmine.Matchers.prototype` well, but it doesn't actually assert statements. I mean following: `expect(false).toBeTruthyCustom()` will execute, but it will not produce a failure. – 18augst Aug 11 '15 at 13:16

mikker · Answer 2 · 2015-05-04T14:05:34.533

14

Here's one for jasmine 2.0+:

beforeEach(function(){
  jasmine.addMatchers({
    toEqualData: function() {
      return {
        compare: function(actual, expected) {
          return { pass: angular.equals(actual, expected) };
        }
      };
    }
  });
});

Note that this uses angular's angular.equals.

edited May 04 '15 at 14:05

answered Apr 24 '15 at 09:35

mikker

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This doesn't work for me.. writing out compare's arguments is always an empty object. – Blake Niemyjski Jul 11 '15 at 17:29
1

That's the answer I've been looking for! – Janusz Kacalak Apr 15 '16 at 15:49
**For detailed answer see:** [Create custom Jasmine-Matcher using Typescript?](https://stackoverflow.com/a/49405171/8740349) – Top-Master Oct 27 '21 at 10:05

Ganesh Sundar C · Answer 3 · 2017-05-04T13:21:10.383

0

Edit: I didn't know it was an internal implementation that may be subjected to change. Use at your own risk.

jasmine.Expectation.addCoreMatchers(matchers)

edited May 04 '17 at 13:21

answered Apr 25 '17 at 05:45

Ganesh Sundar C

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3

Treur · Answer 4 · 2017-06-19T08:54:47.140

Based on previous answers, I created the following setup for angular-cli. I also need an external module in my matcher (in this case moment.js)

Note In this example I added an equalityTester, but it should work with a customer matcher

Create a file src/spec_helper.ts with the following contents:

// Import module
import { Moment } from 'moment';

export function initSpecHelper() {

  beforeEach(() => {
    // Add your matcher
    jasmine.addCustomEqualityTester((a: Moment, b: Moment) => {
      if (typeof a.isSame === 'function') {
        return a.isSame(b);
      }
    });
  });

}

Then, in src/test.ts import the initSpecHelper() function add execute it. I placed it before Angular's TestBed init, wich seems to work just fine.

import { initSpecHelper } from './spec_helper';

//...

// Prevent Karma from running prematurely.
__karma__.loaded = function () {};

// Init our own spec helper
initSpecHelper();

// First, initialize the Angular testing environment.
getTestBed().initTestEnvironment(
  BrowserDynamicTestingModule,
  platformBrowserDynamicTesting()
);

//...

Is there a way to add a Jasmine matcher to the whole environment

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