Issue 6820 - Move tests to mocha

test/elemHide.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 "use strict";
 
+const assert = require("assert");
 const {createSandbox} = require("./_common");
 
 let ElemHide = null;
 let createStyleSheet = null;
 let rulesFromStyleSheet = null;
 let ElemHideExceptions = null;
 let Filter = null;
 let filtersByDomain = null;
 let selectorGroupSize = null;
 
-exports.setUp = function(callback)
+describe("ElemHide", () =>
 {
-  let sandboxedRequire = createSandbox({
-    extraExports: {
-      elemHide: ["filtersByDomain", "selectorGroupSize"]
+  beforeEach(() =>
+  {
+    let sandboxedRequire = createSandbox({
+      extraExports: {
+        elemHide: ["filtersByDomain", "selectorGroupSize"]
+      }
+    });
+    (
+      {ElemHide, createStyleSheet, rulesFromStyleSheet,
+       filtersByDomain, selectorGroupSize} = sandboxedRequire("../lib/elemHide"),
+      {ElemHideExceptions} = sandboxedRequire("../lib/elemHideExceptions"),
+      {Filter} = sandboxedRequire("../lib/filterClasses")
+    );
+  });
+
+  function normalizeSelectors(selectors)
+  {
+    // generateStyleSheetForDomain is currently allowed to return duplicate
+    // selectors for performance reasons, so we need to remove duplicates here.
+    return selectors.slice().sort().filter((selector, index, sortedSelectors) =>
+    {
+      return index == 0 || selector != sortedSelectors[index - 1];
+    });
+  }
+
+  function testResult(domain, expectedSelectors,
+                      {specificOnly = false, expectedExceptions = []} = {})
+  {
+    let normalizedExpectedSelectors = normalizeSelectors(expectedSelectors);
+
+    let {code, selectors, exceptions} =
+        ElemHide.generateStyleSheetForDomain(domain, specificOnly, true, true);
+
+    assert.deepEqual(normalizeSelectors(selectors), normalizedExpectedSelectors);
+
+    // Test for consistency in exception free case.
+    assert.deepEqual(ElemHide.generateStyleSheetForDomain(
+      domain, specificOnly, true, false), {
+        code,
+        selectors,
+        exceptions: null
+      });
+
+    assert.deepEqual(exceptions.map(({text}) => text), expectedExceptions);
+
+    // Make sure each expected selector is in the actual CSS code.
+    for (let selector of normalizedExpectedSelectors)
+    {
+      assert.ok(code.includes(selector + ", ") ||
+                code.includes(selector + " {display: none !important;}\n"));
     }
-  });
-  (
-    {ElemHide, createStyleSheet, rulesFromStyleSheet,
-     filtersByDomain, selectorGroupSize} = sandboxedRequire("../lib/elemHide"),
-    {ElemHideExceptions} = sandboxedRequire("../lib/elemHideExceptions"),
-    {Filter} = sandboxedRequire("../lib/filterClasses")
-  );
-
-  callback();
-};
-
-function normalizeSelectors(selectors)
-{
-  // generateStyleSheetForDomain is currently allowed to return duplicate
-  // selectors for performance reasons, so we need to remove duplicates here.
-  return selectors.slice().sort().filter((selector, index, sortedSelectors) =>
-  {
-    return index == 0 || selector != sortedSelectors[index - 1];
-  });
-}
-
-function testResult(test, domain, expectedSelectors,
-                    {specificOnly = false, expectedExceptions = []} = {})
-{
-  let normalizedExpectedSelectors = normalizeSelectors(expectedSelectors);
-
-  let {code, selectors, exceptions} =
-    ElemHide.generateStyleSheetForDomain(domain, specificOnly, true, true);
-
-  test.deepEqual(normalizeSelectors(selectors), normalizedExpectedSelectors);
-
-  // Test for consistency in exception free case.
-  test.deepEqual(ElemHide.generateStyleSheetForDomain(
-    domain, specificOnly, true, false), {
-      code,
-      selectors,
-      exceptions: null
-    });
-
-  test.deepEqual(exceptions.map(({text}) => text), expectedExceptions);
-
-  // Make sure each expected selector is in the actual CSS code.
-  for (let selector of normalizedExpectedSelectors)
-  {
-    test.ok(code.includes(selector + ", ") ||
-            code.includes(selector + " {display: none !important;}\n"));
   }
-}
-
-exports.testGenerateStyleSheetForDomain = function(test)
-{
-  let addFilter = filterText => ElemHide.add(Filter.fromText(filterText));
-  let removeFilter = filterText => ElemHide.remove(Filter.fromText(filterText));
-  let addException =
-    filterText => ElemHideExceptions.add(Filter.fromText(filterText));
-  let removeException =
-    filterText => ElemHideExceptions.remove(Filter.fromText(filterText));
-
-  testResult(test, "", []);
-
-  addFilter("~foo.example.com,example.com##foo");
-  testResult(test, "barfoo.example.com", ["foo"]);
-  testResult(test, "bar.foo.example.com", []);
-  testResult(test, "foo.example.com", []);
-  testResult(test, "example.com", ["foo"]);
-  testResult(test, "com", []);
-  testResult(test, "", []);
-
-  addFilter("foo.example.com##turnip");
-  testResult(test, "foo.example.com", ["turnip"]);
-  testResult(test, "example.com", ["foo"]);
-  testResult(test, "com", []);
-  testResult(test, "", []);
-
-  addException("example.com#@#foo");
-  testResult(test, "foo.example.com", ["turnip"]);
-  testResult(test, "example.com", [], {
-    expectedExceptions: ["example.com#@#foo"]
-  });
-  testResult(test, "com", []);
-  testResult(test, "", []);
-
-  addFilter("com##bar");
-  testResult(test, "foo.example.com", ["turnip", "bar"]);
-  testResult(test, "example.com", ["bar"], {
-    expectedExceptions: ["example.com#@#foo"]
-  });
-  testResult(test, "com", ["bar"]);
-  testResult(test, "", []);
-
-  addException("example.com#@#bar");
-  testResult(test, "foo.example.com", ["turnip"], {
-    expectedExceptions: ["example.com#@#bar"]
-  });
-  testResult(test, "example.com", [], {
-    expectedExceptions: ["example.com#@#foo", "example.com#@#bar"]
-  });
-  testResult(test, "com", ["bar"]);
-  testResult(test, "", []);
-
-  removeException("example.com#@#foo");
-  testResult(test, "foo.example.com", ["turnip"], {
-    expectedExceptions: ["example.com#@#bar"]
-  });
-  testResult(test, "example.com", ["foo"], {
-    expectedExceptions: ["example.com#@#bar"]
-  });
-  testResult(test, "com", ["bar"]);
-  testResult(test, "", []);
-
-  removeException("example.com#@#bar");
-  testResult(test, "foo.example.com", ["turnip", "bar"]);
-  testResult(test, "example.com", ["foo", "bar"]);
-  testResult(test, "com", ["bar"]);
-  testResult(test, "", []);
-
-  addFilter("##generic");
-  testResult(test, "foo.example.com", ["turnip", "bar", "generic"]);
-  testResult(test, "example.com", ["foo", "bar", "generic"]);
-  testResult(test, "com", ["bar", "generic"]);
-  testResult(test, "", ["generic"]);
-  testResult(test, "foo.example.com", ["turnip", "bar"], {specificOnly: true});
-  testResult(test, "example.com", ["foo", "bar"], {specificOnly: true});
-  testResult(test, "com", ["bar"], {specificOnly: true});
-  testResult(test, "", [], {specificOnly: true});
-  removeFilter("##generic");
-
-  addFilter("~adblockplus.org##example");
-  testResult(test, "adblockplus.org", []);
-  testResult(test, "", ["example"]);
-  testResult(test, "foo.example.com", ["turnip", "bar", "example"]);
-  testResult(test, "foo.example.com", ["turnip", "bar"], {specificOnly: true});
-  removeFilter("~adblockplus.org##example");
-
-  removeFilter("~foo.example.com,example.com##foo");
-  testResult(test, "foo.example.com", ["turnip", "bar"]);
-  testResult(test, "example.com", ["bar"]);
-  testResult(test, "com", ["bar"]);
-  testResult(test, "", []);
-
-  removeFilter("com##bar");
-  testResult(test, "foo.example.com", ["turnip"]);
-  testResult(test, "example.com", []);
-  testResult(test, "com", []);
-  testResult(test, "", []);
-
-  removeFilter("foo.example.com##turnip");
-  testResult(test, "foo.example.com", []);
-  testResult(test, "example.com", []);
-  testResult(test, "com", []);
-  testResult(test, "", []);
-
-  addFilter("example.com##dupe");
-  addFilter("example.com##dupe");
-  testResult(test, "example.com", ["dupe"]);
-  removeFilter("example.com##dupe");
-  testResult(test, "example.com", []);
-  removeFilter("example.com##dupe");
-
-  addFilter("~foo.example.com,example.com##foo");
-
-  addFilter("##foo");
-  testResult(test, "foo.example.com", ["foo"]);
-  testResult(test, "example.com", ["foo"]);
-  testResult(test, "com", ["foo"]);
-  testResult(test, "", ["foo"]);
-  removeFilter("##foo");
-
-  addFilter("example.org##foo");
-  testResult(test, "foo.example.com", []);
-  testResult(test, "example.com", ["foo"]);
-  testResult(test, "com", []);
-  testResult(test, "", []);
-  removeFilter("example.org##foo");
-
-  addFilter("~example.com##foo");
-  testResult(test, "foo.example.com", []);
-  testResult(test, "example.com", ["foo"]);
-  testResult(test, "com", ["foo"]);
-  testResult(test, "", ["foo"]);
-  removeFilter("~example.com##foo");
-
-  removeFilter("~foo.example.com,example.com##foo");
-
-  // Test criteria
-  addFilter("##hello");
-  addFilter("~example.com##world");
-  addFilter("foo.com##specific");
-  testResult(test, "foo.com", ["specific"], {specificOnly: true});
-  testResult(test, "foo.com", ["hello", "specific", "world"]);
-  testResult(test, "example.com", [], {specificOnly: true});
-  removeFilter("foo.com##specific");
-  removeFilter("~example.com##world");
-  removeFilter("##hello");
-  testResult(test, "foo.com", []);
-
-  addFilter("##hello");
-  testResult(test, "foo.com", [], {specificOnly: true});
-  testResult(test, "foo.com", ["hello"]);
-  testResult(test, "bar.com", [], {specificOnly: true});
-  testResult(test, "bar.com", ["hello"]);
-  addException("foo.com#@#hello");
-  testResult(test, "foo.com", [], {specificOnly: true});
-  testResult(test, "foo.com", [], {expectedExceptions: ["foo.com#@#hello"]});
-  testResult(test, "bar.com", [], {specificOnly: true});
-  testResult(test, "bar.com", ["hello"]);
-  removeException("foo.com#@#hello");
-  testResult(test, "foo.com", [], {specificOnly: true});
-  // Note: We don't take care to track conditional selectors which became
-  //       unconditional when a filter was removed. This was too expensive.
-  testResult(test, "foo.com", ["hello"]);
-  testResult(test, "bar.com", [], {specificOnly: true});
-  testResult(test, "bar.com", ["hello"]);
-  removeFilter("##hello");
-  testResult(test, "foo.com", []);
-  testResult(test, "bar.com", []);
-
-  addFilter("##hello");
-  addFilter("foo.com##hello");
-  testResult(test, "foo.com", ["hello"]);
-  removeFilter("foo.com##hello");
-  testResult(test, "foo.com", ["hello"]);
-  removeFilter("##hello");
-  testResult(test, "foo.com", []);
-
-  addFilter("##hello");
-  addFilter("foo.com##hello");
-  testResult(test, "foo.com", ["hello"]);
-  removeFilter("##hello");
-  testResult(test, "foo.com", ["hello"]);
-  removeFilter("foo.com##hello");
-  testResult(test, "foo.com", []);
-
-  test.done();
-};
-
-exports.testZeroFilterKey = function(test)
-{
-  ElemHide.add(Filter.fromText("##test"));
-  ElemHideExceptions.add(Filter.fromText("foo.com#@#test"));
-  testResult(test, "foo.com", [], {expectedExceptions: ["foo.com#@#test"]});
-  testResult(test, "bar.com", ["test"]);
-  test.done();
-};
-
-exports.testFiltersByDomain = function(test)
-{
-  test.equal(filtersByDomain.size, 0);
-
-  ElemHide.add(Filter.fromText("##test"));
-  test.equal(filtersByDomain.size, 0);
-
-  ElemHide.add(Filter.fromText("example.com##test"));
-  test.equal(filtersByDomain.size, 1);
-
-  ElemHide.add(Filter.fromText("example.com,~www.example.com##test"));
-  test.equal(filtersByDomain.size, 2);
-
-  ElemHide.remove(Filter.fromText("example.com##test"));
-  test.equal(filtersByDomain.size, 2);
-
-  ElemHide.remove(Filter.fromText("example.com,~www.example.com##test"));
-  test.equal(filtersByDomain.size, 0);
-
-  test.done();
-};
-
-exports.testCreateStyleSheet = function(test)
-{
-  test.equal(
-    createStyleSheet([
-      "html", "#foo", ".bar", "#foo .bar", "#foo > .bar",
-      "#foo[data-bar='bar']"
-    ]),
-    "html, #foo, .bar, #foo .bar, #foo > .bar, #foo[data-bar='bar'] " +
-    "{display: none !important;}\n",
-    "Style sheet creation should work"
-  );
-
-  let selectors = new Array(50000).fill().map((element, index) => ".s" + index);
-
-  test.equal((createStyleSheet(selectors).match(/\n/g) || []).length,
-             Math.ceil(50000 / selectorGroupSize),
-             "Style sheet should be split up into rules with at most " +
-             selectorGroupSize + " selectors each");
-
-  test.equal(
-    createStyleSheet([
-      "html", "#foo", ".bar", "#foo .bar", "#foo > .bar",
-      "#foo[data-bar='{foo: 1}']"
-    ]),
-    "html, #foo, .bar, #foo .bar, #foo > .bar, " +
-    "#foo[data-bar='\\7B foo: 1\\7D '] {display: none !important;}\n",
-    "Braces should be escaped"
-  );
-
-  test.done();
-};
-
-exports.testRulesFromStyleSheet = function(test)
-{
-  // Note: The rulesFromStyleSheet function assumes that each rule will be
-  // terminated with a newline character, including the last rule. If this is
-  // not the case, the function goes into an infinite loop. It should only be
-  // used with the return value of the createStyleSheet function.
-
-  test.deepEqual([...rulesFromStyleSheet("")], []);
-  test.deepEqual([...rulesFromStyleSheet("#foo {}\n")], ["#foo {}"]);
-  test.deepEqual([...rulesFromStyleSheet("#foo {}\n#bar {}\n")],
-                 ["#foo {}", "#bar {}"]);
-
-  test.done();
-};
+
+  it("Generating Style Sheet", () =>
+  {
+    let addFilter = filterText => ElemHide.add(Filter.fromText(filterText));
+    let removeFilter =
+        filterText => ElemHide.remove(Filter.fromText(filterText));
+    let addException =
+        filterText => ElemHideExceptions.add(Filter.fromText(filterText));
+    let removeException =
+        filterText => ElemHideExceptions.remove(Filter.fromText(filterText));
+
+    testResult("", []);
+
+    addFilter("~foo.example.com,example.com##foo");
+    testResult("barfoo.example.com", ["foo"]);
+    testResult("bar.foo.example.com", []);
+    testResult("foo.example.com", []);
+    testResult("example.com", ["foo"]);
+    testResult("com", []);
+    testResult("", []);
+
+    addFilter("foo.example.com##turnip");
+    testResult("foo.example.com", ["turnip"]);
+    testResult("example.com", ["foo"]);
+    testResult("com", []);
+    testResult("", []);
+
+    addException("example.com#@#foo");
+    testResult("foo.example.com", ["turnip"]);
+    testResult("example.com", [], {
+      expectedExceptions: ["example.com#@#foo"]
+    });
+    testResult("com", []);
+    testResult("", []);
+
+    addFilter("com##bar");
+    testResult("foo.example.com", ["turnip", "bar"]);
+    testResult("example.com", ["bar"], {
+      expectedExceptions: ["example.com#@#foo"]
+    });
+    testResult("com", ["bar"]);
+    testResult("", []);
+
+    addException("example.com#@#bar");
+    testResult("foo.example.com", ["turnip"], {
+      expectedExceptions: ["example.com#@#bar"]
+    });
+    testResult("example.com", [], {
+      expectedExceptions: ["example.com#@#foo", "example.com#@#bar"]
+    });
+    testResult("com", ["bar"]);
+    testResult("", []);
+
+    removeException("example.com#@#foo");
+    testResult("foo.example.com", ["turnip"], {
+      expectedExceptions: ["example.com#@#bar"]
+    });
+    testResult("example.com", ["foo"], {
+      expectedExceptions: ["example.com#@#bar"]
+    });
+    testResult("com", ["bar"]);
+    testResult("", []);
+
+    removeException("example.com#@#bar");
+    testResult("foo.example.com", ["turnip", "bar"]);
+    testResult("example.com", ["foo", "bar"]);
+    testResult("com", ["bar"]);
+    testResult("", []);
+
+    addFilter("##generic");
+    testResult("foo.example.com", ["turnip", "bar", "generic"]);
+    testResult("example.com", ["foo", "bar", "generic"]);
+    testResult("com", ["bar", "generic"]);
+    testResult("", ["generic"]);
+    testResult("foo.example.com", ["turnip", "bar"], {specificOnly: true});
+    testResult("example.com", ["foo", "bar"], {specificOnly: true});
+    testResult("com", ["bar"], {specificOnly: true});
+    testResult("", [], {specificOnly: true});
+    removeFilter("##generic");
+
+    addFilter("~adblockplus.org##example");
+    testResult("adblockplus.org", []);
+    testResult("", ["example"]);
+    testResult("foo.example.com", ["turnip", "bar", "example"]);
+    testResult("foo.example.com", ["turnip", "bar"], {specificOnly: true});
+    removeFilter("~adblockplus.org##example");
+
+    removeFilter("~foo.example.com,example.com##foo");
+    testResult("foo.example.com", ["turnip", "bar"]);
+    testResult("example.com", ["bar"]);
+    testResult("com", ["bar"]);
+    testResult("", []);
+
+    removeFilter("com##bar");
+    testResult("foo.example.com", ["turnip"]);
+    testResult("example.com", []);
+    testResult("com", []);
+    testResult("", []);
+
+    removeFilter("foo.example.com##turnip");
+    testResult("foo.example.com", []);
+    testResult("example.com", []);
+    testResult("com", []);
+    testResult("", []);
+
+    addFilter("example.com##dupe");
+    addFilter("example.com##dupe");
+    testResult("example.com", ["dupe"]);
+    removeFilter("example.com##dupe");
+    testResult("example.com", []);
+    removeFilter("example.com##dupe");
+
+    addFilter("~foo.example.com,example.com##foo");
+
+    addFilter("##foo");
+    testResult("foo.example.com", ["foo"]);
+    testResult("example.com", ["foo"]);
+    testResult("com", ["foo"]);
+    testResult("", ["foo"]);
+    removeFilter("##foo");
+
+    addFilter("example.org##foo");
+    testResult("foo.example.com", []);
+    testResult("example.com", ["foo"]);
+    testResult("com", []);
+    testResult("", []);
+    removeFilter("example.org##foo");
+
+    addFilter("~example.com##foo");
+    testResult("foo.example.com", []);
+    testResult("example.com", ["foo"]);
+    testResult("com", ["foo"]);
+    testResult("", ["foo"]);
+    removeFilter("~example.com##foo");
+
+    removeFilter("~foo.example.com,example.com##foo");
+
+    // Test criteria
+    addFilter("##hello");
+    addFilter("~example.com##world");
+    addFilter("foo.com##specific");
+    testResult("foo.com", ["specific"], {specificOnly: true});
+    testResult("foo.com", ["hello", "specific", "world"]);
+    testResult("example.com", [], {specificOnly: true});
+    removeFilter("foo.com##specific");
+    removeFilter("~example.com##world");
+    removeFilter("##hello");
+    testResult("foo.com", []);
+
+    addFilter("##hello");
+    testResult("foo.com", [], {specificOnly: true});
+    testResult("foo.com", ["hello"]);
+    testResult("bar.com", [], {specificOnly: true});
+    testResult("bar.com", ["hello"]);
+    addException("foo.com#@#hello");
+    testResult("foo.com", [], {specificOnly: true});
+    testResult("foo.com", [], {expectedExceptions: ["foo.com#@#hello"]});
+    testResult("bar.com", [], {specificOnly: true});
+    testResult("bar.com", ["hello"]);
+    removeException("foo.com#@#hello");
+    testResult("foo.com", [], {specificOnly: true});
+    // Note: We don't take care to track conditional selectors which became
+    //       unconditional when a filter was removed. This was too expensive.
+    testResult("foo.com", ["hello"]);
+    testResult("bar.com", [], {specificOnly: true});
+    testResult("bar.com", ["hello"]);
+    removeFilter("##hello");
+    testResult("foo.com", []);
+    testResult("bar.com", []);
+
+    addFilter("##hello");
+    addFilter("foo.com##hello");
+    testResult("foo.com", ["hello"]);
+    removeFilter("foo.com##hello");
+    testResult("foo.com", ["hello"]);
+    removeFilter("##hello");
+    testResult("foo.com", []);
+
+    addFilter("##hello");
+    addFilter("foo.com##hello");
+    testResult("foo.com", ["hello"]);
+    removeFilter("##hello");
+    testResult("foo.com", ["hello"]);
+    removeFilter("foo.com##hello");
+    testResult("foo.com", []);
+  });
+
+  it("Zero filter key", () =>
+  {
+    ElemHide.add(Filter.fromText("##test"));
+    ElemHideExceptions.add(Filter.fromText("foo.com#@#test"));
+    testResult("foo.com", [], {expectedExceptions: ["foo.com#@#test"]});
+    testResult("bar.com", ["test"]);
+  });
+
+  it("Filters by Domain", () =>
+  {
+    assert.equal(filtersByDomain.size, 0);
+
+    ElemHide.add(Filter.fromText("##test"));
+    assert.equal(filtersByDomain.size, 0);
+
+    ElemHide.add(Filter.fromText("example.com##test"));
+    assert.equal(filtersByDomain.size, 1);
+
+    ElemHide.add(Filter.fromText("example.com,~www.example.com##test"));
+    assert.equal(filtersByDomain.size, 2);
+
+    ElemHide.remove(Filter.fromText("example.com##test"));
+    assert.equal(filtersByDomain.size, 2);
+
+    ElemHide.remove(Filter.fromText("example.com,~www.example.com##test"));
+    assert.equal(filtersByDomain.size, 0);
+  });
+
+  describe("Creating Stylesheet", () =>
+  {
+    it("Basic creation", () =>
+    {
+      assert.equal(
+        createStyleSheet([
+          "html", "#foo", ".bar", "#foo .bar", "#foo > .bar",
+          "#foo[data-bar='bar']"
+        ]),
+        "html, #foo, .bar, #foo .bar, #foo > .bar, #foo[data-bar='bar'] " +
+          "{display: none !important;}\n",
+        "Style sheet creation should work"
+      );
+    });
+
+    it("Splitting", () =>
+    {
+      let selectors = new Array(50000).fill().map((element, index) => ".s" + index);
+
+      assert.equal((createStyleSheet(selectors).match(/\n/g) || []).length,
+                   Math.ceil(50000 / selectorGroupSize),
+                   "Style sheet should be split up into rules with at most " +
+                   selectorGroupSize + " selectors each");
+    });
+
+    it("Escaping", () =>
+    {
+      assert.equal(
+        createStyleSheet([
+          "html", "#foo", ".bar", "#foo .bar", "#foo > .bar",
+          "#foo[data-bar='{foo: 1}']"
+        ]),
+        "html, #foo, .bar, #foo .bar, #foo > .bar, " +
+          "#foo[data-bar='\\7B foo: 1\\7D '] {display: none !important;}\n",
+        "Braces should be escaped"
+      );
+    });
+  });
+
+  it("Rules from StyleSheet", () =>
+  {
+    // Note: The rulesFromStyleSheet function assumes that each rule will be
+    // terminated with a newline character, including the last rule. If this is
+    // not the case, the function goes into an infinite loop. It should only be
+    // used with the return value of the createStyleSheet function.
+
+    assert.deepEqual([...rulesFromStyleSheet("")], []);
+    assert.deepEqual([...rulesFromStyleSheet("#foo {}\n")], ["#foo {}"]);
+    assert.deepEqual([...rulesFromStyleSheet("#foo {}\n#bar {}\n")],
+                   ["#foo {}", "#bar {}"]);
+  });
+});