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// Copyright 2009 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
goog.provide('goog.testing.PseudoRandomTest');
goog.setTestOnly('goog.testing.PseudoRandomTest');
goog.require('goog.testing.PseudoRandom');
goog.require('goog.testing.jsunit');
function runFairnessTest(sides, rolls, chiSquareLimit) {
// Initialize the count table for dice rolls.
var counts = [];
for (var i = 0; i < sides; ++i) {
counts[i] = 0;
}
// Roll the dice many times and count the results.
for (var i = 0; i < rolls; ++i) {
++counts[Math.floor(Math.random() * sides)];
}
// If the dice is fair, we expect a uniform distribution.
var expected = rolls / sides;
// Pearson's chi-square test for a distribution fit.
var chiSquare = 0;
for (var i = 0; i < sides; ++i) {
chiSquare += (counts[i] - expected) * (counts[i] - expected) / expected;
}
assert(
'Chi-square test for a distribution fit failed',
chiSquare < chiSquareLimit);
}
function testInstall() {
var random = new goog.testing.PseudoRandom();
var originalRandom = Math.random;
assertFalse(!!random.installed_);
random.install();
assertTrue(random.installed_);
assertNotEquals(Math.random, originalRandom);
random.uninstall();
assertFalse(random.installed_);
assertEquals(originalRandom, Math.random);
}
function testBounds() {
var random = new goog.testing.PseudoRandom();
random.install();
for (var i = 0; i < 100000; ++i) {
var value = Math.random();
assert('Random value out of bounds', value >= 0 && value < 1);
}
random.uninstall();
}
function testFairness() {
var random = new goog.testing.PseudoRandom(0, true);
// Chi-square statistics: p-value = 0.05, df = 5, limit = 11.07.
runFairnessTest(6, 100000, 11.07);
// Chi-square statistics: p-value = 0.05, df = 100, limit = 124.34.
runFairnessTest(101, 100000, 124.34);
random.uninstall();
}
function testReseed() {
var random = new goog.testing.PseudoRandom(100, true);
var sequence = [];
for (var i = 0; i < 64000; ++i) {
sequence.push(Math.random());
}
random.seed(100);
for (var i = 0; i < sequence.length; ++i) {
assertEquals(sequence[i], Math.random());
}
random.uninstall();
}
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