Documentation Home Behavior-Driven JavaScript
This page is for an older version of Jasmine (2.1)
The current stable version of Jasmine is: 5.4 - You can also look at the docs for the next release: Edge

custom_equality.js

Custom Equality Testers

 
describe("custom equality", function() {

You can customize how jasmine determines if two objects are equal by defining your own custom equality testers. A custom equality tester is a function that takes two arguments.

 
  var myCustomEquality = function(first, second) {

If the custom equality tester knows how to compare the two items, it should return either true or false

 
    if (typeof first == "string" && typeof second == "string") {
    return first[0] == second[1];
  }

Otherwise, it should return undefined, to tell jasmine's equality tester that it can't compare the items

 
  };

Then you register your tester in a beforeEach so jasmine knows about it.

 
  beforeEach(function() {
  jasmine.addCustomEqualityTester(myCustomEquality);
});

Then when you do comparisons in a spec, custom equality testers will be checked first before the default equality logic.

 
  it("should be custom equal", function() {
  expect("abc").toEqual("aaa");
});

If your custom tester returns false, no other equality checking will be done.

 
  it("should be custom not equal", function() {
  expect("abc").not.toEqual("abc");
});
});