Inject a custom AngularJS filter object to a (Jasmine) unit test spec.

InjectAngularJSFilterToJasmine.js

// Simple custom filer
var filters = angular.module('myNameSpace.filters', []);

filters.filter('reverse', function() {
  return function(text) {
    return text.split('').reverse().join('');
  };
});

// 2 ways to test

// Method 1
describe('myNameSpace.filters', function() {
  describe('EchoService', function() {
    var createFilter;

    beforeEach(module('myNameSpace.filters'));

    beforeEach(inject(function($filter) {
      createFilter = function() {
        return $filter('reverse');
      };
    }));

    it('should reverse', function() {
      var filter = createFilter();
      expect(filter('hello')).toBe('olleh');
    });
  });
});

// Method 2 (Shorter Version)
describe('myNameSpace.filters', function() {
  describe('EchoService', function() {
    beforeEach(module('angularjs.testing.filters'));

    it('should reverse', inject(function($filter) {
      var reversedText = $filter('reverse')('hello');
      expect(reversedText).toBe('olleh');
    }));
  });
});