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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");
  });
});