Inject $filter and then call it with $filter('filterName')(input, options);

So to test the equivalent of this template {{ foo | testFilter:capitalize }}

describe('The test filter', function () {

  'use strict'; 



  var $filter;



  beforeEach(function () {

    module('myTestFilterModule');



    inject(function (_$filter_) {

      $filter = _$filter_;

    });

  });



  it('should capitalize a string', function () {

    // Arrange.

    var foo = 'hello world', result;



    // Act.

    result = $filter('testFilter')(foo, 'capitalize');



    // Assert.

    expect(result).toEqual('HELLO WORLD');

  });

});