Allow tests to pass in a mock Intl

Make Intl an optional argument in time.js so that tests can pass in a
mock Intl (or null) instead of having to patch window.Intl.

h/static/scripts/test/time-test.js

@@ -52,15 +52,8 @@ describe('time', function () {
 
   describe('.toFuzzyString', function () {
 
-    var originalIntl;
-
-    before(function () {
-
-      // Intl isn't implemented in PhantomJS so we have to mock it in these
-      // tests. The mock version returns the results we'd expect from the real
-      // one for the test values that we use.
-      originalIntl = window.Intl;
-      window.Intl = {
+    function mockIntl() {
+      return {
         DateTimeFormat: function () {
           return {
             format: function () {
@@ -73,16 +66,12 @@ describe('time', function () {
           };
         }
       };
-    });
-
-    after(function () {
-      window.Intl = originalIntl;
-    });
+    }
 
     it('Handles empty dates', function () {
       var t = null;
       var expect = '';
-      assert.equal(time.toFuzzyString(t), expect);
+      assert.equal(time.toFuzzyString(t, mockIntl()), expect);
     });
 
     var testFixture = function (f) {
@@ -90,7 +79,7 @@ describe('time', function () {
         var t = new Date();
         var expect = f[1];
         sandbox.clock.tick(f[0] * 1000);
-        assert.equal(time.toFuzzyString(t), expect);
+        assert.equal(time.toFuzzyString(t, mockIntl()), expect);
       };
     };
 
@@ -103,21 +92,19 @@ describe('time', function () {
     it('falls back to simple strings for >24hrs ago', function () {
       // If window.Intl is not available then the date formatting for dates
       // more than one day ago falls back to a simple date string.
-      window.Intl = undefined;
       var d = new Date();
       sandbox.clock.tick(day * 2 * 1000);
 
-      assert.equal(time.toFuzzyString(d), 'Thu Jan 01 1970');
+      assert.equal(time.toFuzzyString(d, null), 'Thu Jan 01 1970');
     });
 
     it('falls back to simple strings for >1yr ago', function () {
       // If window.Intl is not available then the date formatting for dates
       // more than one year ago falls back to a simple date string.
-      window.Intl = undefined;
       var d = new Date();
       sandbox.clock.tick(year * 2 * 1000);
 
-      assert.equal(time.toFuzzyString(d), 'Thu Jan 01 1970');
+      assert.equal(time.toFuzzyString(d, null), 'Thu Jan 01 1970');
     });
 
   });

h/static/scripts/time.js

@@ -54,8 +54,14 @@ var formatters = {};
  * @returns {string}
  *
  */
-function format(date, options) {
-  if (typeof Intl !== 'undefined' && Intl.DateTimeFormat) {
+function format(date, options, Intl) {
+  // If the tests have passed in a mock Intl then use it, otherwise use the
+  // real one.
+  if (typeof Intl === 'undefined') {
+    Intl = window.Intl;
+  }
+
+  if (Intl && Intl.DateTimeFormat) {
     var key = JSON.stringify(options);
     var formatter = formatters[key];
 
@@ -71,19 +77,12 @@ function format(date, options) {
   }
 }
 
-function dayAndMonth(date) {
-  return format(date, {
-    month: 'short',
-    day: '2-digit',
-  });
+function dayAndMonth(date, now, Intl) {
+  return format(date, {month: 'short', day: '2-digit'}, Intl);
 }
 
-function dayAndMonthAndYear(date) {
-  return format(date, {
-    day: '2-digit',
-    month: 'short',
-    year: 'numeric'
-  });
+function dayAndMonthAndYear(date, now, Intl) {
+  return format(date, {day: '2-digit', month: 'short', year: 'numeric'}, Intl);
 }
 
 var BREAKPOINTS = [
@@ -186,13 +185,13 @@ function decayingInterval(date, callback) {
  * @param {number} date - The absolute timestamp to format.
  * @return {string} A 'fuzzy' string describing the relative age of the date.
  */
-function toFuzzyString(date) {
+function toFuzzyString(date, Intl) {
   if (!date) {
     return '';
   }
   var now = new Date();
 
-  return getBreakpoint(date, now).format(new Date(date), now);
+  return getBreakpoint(date, now).format(new Date(date), now, Intl);
 }
 
 module.exports = {