jsPsych/tests/jsPsych.randomization/randomziation.test.js

const root = '../../';

require(root + 'jspsych.js');

const originalRandomFunction = Math.random;

describe('#shuffle', function(){
  test('should produce fixed order with mock RNG', function(){
    Math.random = jest.fn().mockImplementation(function(){ return 0.5; });
    var arr = [1,2,3,4,5,6];
    expect(jsPsych.randomization.shuffle(arr)).toEqual([1,6,2,5,3,4]);
  });
});

describe('shuffleAlternateGroups', function(){
  test('should shuffle in alternating groups', function(){
    Math.random = jest.fn().mockImplementation(function(){ return 0.5; });
    var toShuffle = [['a','b','c',], [1,2,3]];
    expect(jsPsych.randomization.shuffleAlternateGroups(toShuffle)).toEqual(['a',1,'c',3,'b',2]);
  });
})

describe('#randomID', function(){
  test('should produce ID based on mock RNG', function(){
    Math.random = jest.fn().mockReturnValueOnce(0.1).mockReturnValueOnce(0.2).mockReturnValueOnce(0.3);
    expect(jsPsych.randomization.randomID(3)).toBe("37a");
  });
});

describe('shuffleNoRepeats', function(){
  test('should generate a random order with no repeats', function(){
    if(typeof Math.random.mock !== 'undefined'){
      Math.random = originalRandomFunction;
    }
    var equalityTest = function(a,b){ return a === b };
    var toShuffle = ['a','b','c','d'];
    var repeated = jsPsych.randomization.repeat(toShuffle, 20);
    var randomOrder = jsPsych.randomization.shuffleNoRepeats(repeated, equalityTest);
    var repeats = 0;
    for(var i=1; i<randomOrder.length; i++){
      if(equalityTest(randomOrder[i], randomOrder[i-1])) { repeats++; }
    }
    expect(repeats).toBe(0);
  })
})