LibJS: Convert remaining top-level tests to new system

18 files changed, 470 insertions, 498 deletions

diff --git a/Libraries/LibJS/Tests/const-reassignment.js b/Libraries/LibJS/Tests/const-reassignment.js
new file mode 100644
index 0000000000..6638229738
--- /dev/null
+++ b/Libraries/LibJS/Tests/const-reassignment.js
@@ -0,0 +1,16 @@
+test.skip("reassignment to const", () => {
+  const constantValue = 1;
+  expect(() => {
+    constantValue = 2;
+  }).toThrowWithMessage(TypeError, "Invalid assignment to const variable");
+  expect(constantValue).toBe(1);
+});
+
+test("const creation in inner scope", () => {
+  const constantValue = 1;
+  do {
+    const constantValue = 2;
+    expect(constantValue).toBe(2);
+  } while (false);
+  expect(constantValue).toBe(1);
+});
diff --git a/Libraries/LibJS/Tests/object-basic.js b/Libraries/LibJS/Tests/object-basic.js
index d4d0b83e79..d35ff1ed06 100644
--- a/Libraries/LibJS/Tests/object-basic.js
+++ b/Libraries/LibJS/Tests/object-basic.js
@@ -1,104 +1,149 @@
-load("test-common.js");
-
-try {
-  var foo = "bar";
-  var computed = "computed";
-  var o = {
-    1: 23,
-    foo,
-    bar: "baz",
-    qux: true ? 10 : 20,
-    hello: "friends",
-    [1 + 2]: 42,
-    ["I am a " + computed + " key"]: foo,
-    duplicate: "hello",
-    duplicate: "world",
-  };
-  assert(o[1] === 23);
-  assert(o[1n] === 23);
-  assert(o["1"] === 23);
-  assert(o.foo === "bar");
-  assert(o["foo"] === "bar");
-  assert(o.qux === 10), assert(o.hello === "friends");
-  assert(o["hello"] === "friends");
-  assert(o[3] === 42);
-  assert(o["I am a computed key"] === "bar");
-  assert(o.duplicate === "world");
-  o.baz = "test";
-  assert(o.baz === "test");
-  assert(o["baz"] === "test");
-  o[10] = "123";
-  assert(o[10] === "123");
-  assert(o["10"] === "123");
-  o[10n] = "123";
-  assert(o[10] === "123");
-  assert(o["10"] === "123");
-  o[-1] = "hello friends";
-  assert(o[-1] === "hello friends");
-  assert(o["-1"] === "hello friends");
-
-  var math = { 3.14: "pi" };
-  assert(math["3.14"] === "pi");
-  // Note : this test doesn't pass yet due to floating-point literals being coerced to i32 on access
-  // assert(math[3.14] === "pi");
-
-  // This is also allowed! Watch out for syntax errors.
-  var o2 = { return: 1, yield: 1, for: 1, catch: 1, break: 1 };
-  assert(o2.return === 1);
-  assert(o2.yield === 1);
-  assert(o2.for === 1);
-  assert(o2.catch === 1);
-  assert(o2.break === 1);
-
-  var a;
-  var append = x => {
+describe("correct behavior", () => {
+  test("numeric indexing", () => {
+    const o = { 1: 23 };
+
+    expect(o[1]).toBe(23);
+    expect(o[1n]).toBe(23);
+    expect(o["1"]).toBe(23);
+
+    o[10] = "123";
+    expect(o[10]).toBe("123");
+    expect(o["10"]).toBe("123");
+
+    o[10n] = "1234";
+    expect(o[10]).toBe("1234");
+    expect(o["10"]).toBe("1234");
+  });
+
+  test("string indexing", () => {
+    let foo = "bar";
+
+    const o = {
+      foo,
+      bar: "baz",
+      qux: true ? 10 : 20,
+      hello: "friends",
+    };
+
+    expect(o.foo).toBe("bar");
+    expect(o["foo"]).toBe("bar");
+    expect(o.qux).toBe(10), expect(o.hello).toBe("friends");
+    expect(o["hello"]).toBe("friends");
+  });
+
+  test("computed properties", () => {
+    const foo = "bar";
+    const computed = "computed";
+    const o = {
+      [1 + 2]: 42,
+      [`I am a ${computed} key`]: foo,
+    };
+
+    expect(o[3]).toBe(42);
+    expect(o["I am a computed key"]).toBe("bar");
+  });
+
+  test("duplicate keys", () => {
+    const o = {
+      duplicate: "hello",
+      duplicate: "world",
+    };
+    expect(o.duplicate).toBe("world");
+  });
+
+  test("assigning after creation", () => {
+    const o = {};
+    o.baz = "test";
+
+    expect(o.baz).toBe("test");
+    expect(o["baz"]).toBe("test");
+
+    expect(o[-1]).toBeUndefined();
+    o[-1] = "hello friends";
+    expect(o[-1]).toBe("hello friends");
+    expect(o["-1"]).toBe("hello friends");
+  });
+
+  test("floating point keys", () => {
+    const math = { 3.14: "pi" };
+    expect(math["3.14"]).toBe("pi");
+    // FIXME: Floating point literals are coerced to i32
+    // expect(math[3.14]).toBe("pi");
+  });
+
+  test("keywords as property keys", () => {
+    const o2 = {
+      return: 1,
+      yield: 1,
+      for: 1,
+      catch: 1,
+      break: 1,
+    };
+
+    expect(o2.return).toBe(1);
+    expect(o2.yield).toBe(1);
+    expect(o2.for).toBe(1);
+    expect(o2.catch).toBe(1);
+    expect(o2.break).toBe(1);
+  });
+
+  test("prototypical inheritance", () => {
+    var base = {
+      getNumber() {
+        return 10;
+      },
+    };
+
+    var derived = {
+      getNumber() {
+        return 20 + super.getNumber();
+      },
+    };
+
+    Object.setPrototypeOf(derived, base);
+    expect(derived.getNumber()).toBe(30);
+  });
+});
+
+describe("side effects", () => {
+  let a;
+  const append = x => {
     a.push(x);
   };
 
-  a = [];
-  var o3 = { [append(1)]: 1, [append(2)]: 2, [append(3)]: 3 };
-  assert(a.length === 3);
-  assert(a[0] === 1);
-  assert(a[1] === 2);
-  assert(a[2] === 3);
-  assert(o3.undefined === 3);
-
-  a = [];
-  var o4 = { test: append(1), test: append(2), test: append(3) };
-  assert(a.length === 3);
-  assert(a[0] === 1);
-  assert(a[1] === 2);
-  assert(a[2] === 3);
-  assert(o4.test === undefined);
-
-  var base = {
-    getNumber() {
-      return 10;
-    },
-  };
+  test("computed key side effects", () => {
+    a = [];
+    const o3 = { [append(1)]: 1, [append(2)]: 2, [append(3)]: 3 };
+    expect(a).toHaveLength(3);
+    expect(a[0]).toBe(1);
+    expect(a[1]).toBe(2);
+    expect(a[2]).toBe(3);
+    expect(o3.undefined).toBe(3);
+  });
 
-  var derived = {
-    getNumber() {
-      return 20 + super.getNumber();
-    },
-  };
+  test("value side effects", () => {
+    a = [];
+    const o4 = { test: append(1), test: append(2), test: append(3) };
+    expect(a).toHaveLength(3);
+    expect(a[0]).toBe(1);
+    expect(a[1]).toBe(2);
+    expect(a[2]).toBe(3);
+    expect(o4.test).toBeUndefined();
+  });
+});
 
-  Object.setPrototypeOf(derived, base);
-  assert(derived.getNumber() === 30);
-
-  assertIsSyntaxError("({ foo: function() { super.bar; } })");
-  assertIsSyntaxError("({ get ...foo })");
-  assertIsSyntaxError("({ get... foo })");
-  assertIsSyntaxError("({ get foo })");
-  assertIsSyntaxError("({ get foo: bar })");
-  assertIsSyntaxError("({ get [foo]: bar })");
-  assertIsSyntaxError("({ get ...[foo] })");
-  assertIsSyntaxError("({ get foo(bar) {} })");
-  assertIsSyntaxError("({ set foo() {} })");
-  assertIsSyntaxError("({ set foo(bar, baz) {} })");
-  assertIsSyntaxError("({ ...foo: bar })");
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+describe("errors", () => {
+  test("syntax errors", () => {
+    expect("({ foo: function() { super.bar; } })").not.toEval();
+    expect("({ get ...foo })").not.toEval();
+    expect("({ get... foo })").not.toEval();
+    expect("({ get foo })").not.toEval();
+    expect("({ get foo: bar })").not.toEval();
+    expect("({ get [foo]: bar })").not.toEval();
+    expect("({ get ...[foo] })").not.toEval();
+    expect("({ get foo(bar) {} })").not.toEval();
+    expect("({ set foo() {} })").not.toEval();
+    expect("({ set foo(bar, baz) {} })").not.toEval();
+    expect("({ ...foo: bar })").not.toEval();
+  });
+});
diff --git a/Libraries/LibJS/Tests/parser-unary-associativity.js b/Libraries/LibJS/Tests/parser-unary-associativity.js
index 4ed4b015ff..cc22b39660 100644
--- a/Libraries/LibJS/Tests/parser-unary-associativity.js
+++ b/Libraries/LibJS/Tests/parser-unary-associativity.js
@@ -1,20 +1,14 @@
-load("test-common.js");
-
-try {
-  var o = {};
+test("basic functionality", () => {
+  const o = {};
   o.a = 1;
 
-  assert(o.a === 1);
-  assert(!o.a === false);
-  assert(!o.a === !o.a);
-  assert(~o.a === ~o.a);
-  assert(+o.a === +o.a);
-  assert(-o.a === -o.a);
-
-  assert((typeof "x" === "string") === true);
-  assert(!(typeof "x" === "string") === false);
+  expect(o.a === 1).toBeTrue();
+  expect(!o.a === false).toBeTrue();
+  expect(!o.a === !o.a).toBeTrue();
+  expect(~o.a === ~o.a).toBeTrue();
+  expect(+o.a === +o.a).toBeTrue();
+  expect(-o.a === -o.a).toBeTrue();
 
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+  expect((typeof "x" === "string") === true).toBeTrue();
+  expect(!(typeof "x" === "string") === false).toBeTrue();
+});
diff --git a/Libraries/LibJS/Tests/program-strict-mode.js b/Libraries/LibJS/Tests/program-strict-mode.js
index 6d896750b0..87b9da1cbf 100644
--- a/Libraries/LibJS/Tests/program-strict-mode.js
+++ b/Libraries/LibJS/Tests/program-strict-mode.js
@@ -1,29 +1,18 @@
 "use strict";
 
-load("test-common.js");
-
-try {
-  assert(isStrictMode());
-
-  (function () {
-    assert(isStrictMode());
-  })();
+test("basic functionality", () => {
+  expect(isStrictMode()).toBeTrue();
 
   (function () {
-    "use strict";
-    assert(isStrictMode());
+    expect(isStrictMode()).toBeTrue();
   })();
 
   (() => {
-    assert(isStrictMode());
+    expect(isStrictMode()).toBeTrue();
   })();
 
   (() => {
     "use strict";
-    assert(isStrictMode());
+    expect(isStrictMode()).toBeTrue();
   })();
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+});
diff --git a/Libraries/LibJS/Tests/strict-mode-errors.js b/Libraries/LibJS/Tests/strict-mode-errors.js
index 6557650652..827667b729 100644
--- a/Libraries/LibJS/Tests/strict-mode-errors.js
+++ b/Libraries/LibJS/Tests/strict-mode-errors.js
@@ -1,21 +1,9 @@
 "use strict";
 
-load("test-common.js");
-
-try {
+test("basic functionality", () => {
   [true, false, "foo", 123].forEach(primitive => {
-    assertThrowsError(
-      () => {
-        primitive.foo = "bar";
-      },
-      {
-        error: TypeError,
-        message: "Cannot assign property foo to primitive value",
-      }
-    );
+    expect(() => {
+      primitive.foo = "bar";
+    }).toThrowWithMessage(TypeError, "Cannot assign property foo to primitive value");
   });
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+});
diff --git a/Libraries/LibJS/Tests/string-escapes.js b/Libraries/LibJS/Tests/string-escapes.js
index c3242c7924..e6d9752695 100644
--- a/Libraries/LibJS/Tests/string-escapes.js
+++ b/Libraries/LibJS/Tests/string-escapes.js
@@ -1,17 +1,13 @@
-load("test-common.js");
+test("hex escapes", () => {
+  expect("\x55").toBe("U");
+  expect("X55").toBe("X55");
+  expect(`\x55`).toBe("U");
+  expect(`\X55`).toBe("X55");
+});
 
-try {
-  assert("\x55" === "U");
-  assert("X55" === "X55");
-  assert(`\x55` === "U");
-  assert(`\X55` === "X55");
-
-  assert("\u26a0" === "⚠");
-  assert(`\u26a0` === "⚠");
-  assert("\u{1f41e}" === "🐞");
-  assert(`\u{1f41e}` === "🐞");
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+test("unicode escapes", () => {
+  expect("\u26a0").toBe("⚠");
+  expect(`\u26a0`).toBe("⚠");
+  expect("\u{1f41e}").toBe("🐞");
+  expect(`\u{1f41e}`).toBe("🐞");
+});
diff --git a/Libraries/LibJS/Tests/string-spread.js b/Libraries/LibJS/Tests/string-spread.js
index cca1ab60bf..5443e997eb 100644
--- a/Libraries/LibJS/Tests/string-spread.js
+++ b/Libraries/LibJS/Tests/string-spread.js
@@ -1,27 +1,25 @@
-load("test-common.js");
-
 function testArray(arr) {
   return arr.length === 4 && arr[0] === "a" && arr[1] === "b" && arr[2] === "c" && arr[3] === "d";
 }
 
-try {
-  var arr;
-
-  arr = ["a", ..."bc", "d"];
-  assert(testArray(arr));
+test("spreading string literal", () => {
+  expect(["a", ..."bc", "d"]).toEqual(["a", "b", "c", "d"]);
+});
 
-  let s = "bc";
-  arr = ["a", ...s, "d"];
-  assert(testArray(arr));
+test("spreading string variable", () => {
+  const s = "bc";
+  expect(["a", ...s, "d"]).toEqual(["a", "b", "c", "d"]);
+});
 
-  let obj = { a: "bc" };
-  arr = ["a", ...obj.a, "d"];
-  assert(testArray(arr));
+test("spreading string in object", () => {
+  const obj = { a: "bc" };
+  expect(["a", ...obj.a, "d"]).toEqual(["a", "b", "c", "d"]);
+});
 
-  arr = [..."", ...[...new String("abc")], "d"];
-  assert(testArray(arr));
+test("spreading empty string", () => {
+  expect([..."", "a", ..."bc", ..."", "d", ...""]).toEqual(["a", "b", "c", "d"]);
+});
 
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+test("spreading string objects", () => {
+  expect([..."", ...[...new String("abc")], "d"]).toEqual(["a", "b", "c", "d"]);
+});
diff --git a/Libraries/LibJS/Tests/switch-break.js b/Libraries/LibJS/Tests/switch-break.js
index ea0ceaef97..3eb8946d35 100644
--- a/Libraries/LibJS/Tests/switch-break.js
+++ b/Libraries/LibJS/Tests/switch-break.js
@@ -1,9 +1,7 @@
-load("test-common.js");
-
-try {
-  var i = 0;
-  var three;
-  var five;
+test("basic functionality", () => {
+  let i = 0;
+  let three;
+  let five;
 
   for (; i < 9; ) {
     switch (i) {
@@ -16,8 +14,7 @@ try {
     }
     ++i;
   }
-  assert(three === 3);
-  assert(five === 5);
 
-  console.log("PASS");
-} catch {}
+  expect(three).toBe(3);
+  expect(five).toBe(5);
+});
diff --git a/Libraries/LibJS/Tests/template-literals.js b/Libraries/LibJS/Tests/template-literals.js
index aac01b5025..bf089f8e26 100644
--- a/Libraries/LibJS/Tests/template-literals.js
+++ b/Libraries/LibJS/Tests/template-literals.js
@@ -1,50 +1,58 @@
-load("test-common.js");
-
-try {
-  assert(`foo` === "foo");
-  assert(`foo{` === "foo{");
-  assert(`foo}` === "foo}");
-  assert(`foo$` === "foo$");
-  assert(`foo\`` === "foo`");
-  assert(`foo\$` === "foo$");
-
-  assert(`foo ${undefined}` === "foo undefined");
-  assert(`foo ${null}` === "foo null");
-  assert(`foo ${5}` === "foo 5");
-  assert(`foo ${true}` === "foo true");
-  assert(`foo ${"bar"}` === "foo bar");
-  assert(`foo \${"bar"}` === 'foo ${"bar"}');
-
-  assert(`foo ${{}}` === "foo [object Object]");
-  assert(`foo ${{ bar: { baz: "qux" } }}` === "foo [object Object]");
-  assert(`foo ${"bar"} ${"baz"}` === "foo bar baz");
-  assert(`${"foo"} bar baz` === "foo bar baz");
-  assert(`${"foo bar baz"}` === "foo bar baz");
+test("plain literals with expression-like characters", () => {
+  expect(`foo`).toBe("foo");
+  expect(`foo{`).toBe("foo{");
+  expect(`foo}`).toBe("foo}");
+  expect(`foo$`).toBe("foo$");
+});
 
+test("plain literals with escaped special characters", () => {
+  expect(`foo\``).toBe("foo`");
+  expect(`foo\$`).toBe("foo$");
+  expect(`foo \${"bar"}`).toBe('foo ${"bar"}');
+});
+
+test("literals in expressions", () => {
+  expect(`foo ${undefined}`).toBe("foo undefined");
+  expect(`foo ${null}`).toBe("foo null");
+  expect(`foo ${5}`).toBe("foo 5");
+  expect(`foo ${true}`).toBe("foo true");
+  expect(`foo ${"bar"}`).toBe("foo bar");
+});
+
+test("objects in expressions", () => {
+  expect(`foo ${{}}`).toBe("foo [object Object]");
+  expect(`foo ${{ bar: { baz: "qux" } }}`).toBe("foo [object Object]");
+});
+
+test("expressions at beginning of template literal", () => {
+  expect(`${"foo"} bar baz`).toBe("foo bar baz");
+  expect(`${"foo bar baz"}`).toBe("foo bar baz");
+});
+
+test("multiple template literals", () => {
+  expect(`foo ${"bar"} ${"baz"}`).toBe("foo bar baz");
+});
+
+test("variables in expressions", () => {
   let a = 27;
-  assert(`${a}` === "27");
-  assert(`foo ${a}` === "foo 27");
-  assert(`foo ${a ? "bar" : "baz"}` === "foo bar");
-  assert(`foo ${(() => a)()}` === "foo 27");
-
-  assert(`foo ${`bar`}` === "foo bar");
-  assert(`${`${`${`${"foo"}`} bar`}`}` === "foo bar");
-  assert(
+  expect(`${a}`).toBe("27");
+  expect(`foo ${a}`).toBe("foo 27");
+  expect(`foo ${a ? "bar" : "baz"}`).toBe("foo bar");
+  expect(`foo ${(() => a)()}`).toBe("foo 27");
+});
+
+test("template literals in expressions", () => {
+  expect(`foo ${`bar`}`).toBe("foo bar");
+  expect(`${`${`${`${"foo"}`} bar`}`}`).toBe("foo bar");
+});
+
+test("newline literals (not characters)", () => {
+  expect(
     `foo
-    bar` === "foo\n    bar"
-  );
-
-  assertThrowsError(
-    () => {
-      `${b}`;
-    },
-    {
-      error: ReferenceError,
-      message: "'b' is not defined",
-    }
-  );
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+    bar`
+  ).toBe("foo\n    bar");
+});
+
+test("reference error from expressions", () => {
+  expect(() => `${b}`).toThrowWithMessage(ReferenceError, "'b' is not defined");
+});
diff --git a/Libraries/LibJS/Tests/throw-basic.js b/Libraries/LibJS/Tests/throw-basic.js
index 733b14f80a..e359a24aa1 100644
--- a/Libraries/LibJS/Tests/throw-basic.js
+++ b/Libraries/LibJS/Tests/throw-basic.js
@@ -1,30 +1,34 @@
-load("test-common.js");
+test("throw literal", () => {
+  try {
+    throw 1;
+    expect().fail();
+  } catch (e) {
+    if (e.name === "ExpectationError") throw e;
+    expect(e).toBe(1);
+  }
+});
 
-try {
-  throw 1;
-  assertNotReached();
-} catch (e) {
-  assert(e === 1);
-}
+test("throw array", () => {
+  try {
+    throw [99];
+    expect().fail();
+  } catch (e) {
+    if (e.name === "ExpectationError") throw e;
+    expect(e).toEqual([99]);
+  }
+});
 
-try {
-  throw [99];
-  assertNotReached();
-} catch (e) {
-  assert(typeof e === "object");
-  assert(e.length === 1);
-}
+test("call function that throws", () => {
+  function foo() {
+    throw "hello";
+    expect().fail();
+  }
 
-function foo() {
-  throw "hello";
-  assertNotReached();
-}
-
-try {
-  foo();
-  assertNotReached();
-} catch (e) {
-  assert(e === "hello");
-}
-
-console.log("PASS");
+  try {
+    foo();
+    expect().fail();
+  } catch (e) {
+    if (e.name === "ExpectationError") throw e;
+    expect(e).toBe("hello");
+  }
+});
diff --git a/Libraries/LibJS/Tests/to-number-basic.js b/Libraries/LibJS/Tests/to-number-basic.js
index 91a1f00b10..5b80f24d53 100644
--- a/Libraries/LibJS/Tests/to-number-basic.js
+++ b/Libraries/LibJS/Tests/to-number-basic.js
@@ -1,62 +1,75 @@
-load("test-common.js");
-
-try {
-  assert(+false === 0);
-  assert(-false === 0);
-  assert(+true === 1);
-  assert(-true === -1);
-  assert(+null === 0);
-  assert(-null === 0);
-  assert(+[] === 0);
-  assert(-[] === 0);
-  assert(+[,] === 0);
-  assert(-[,] === 0);
-  assert(+[null] === 0);
-  assert(-[null] === 0);
-  assert(+[undefined] === 0);
-  assert(-[undefined] === 0);
-  assert(+[[[[[]]]]] === 0);
-  assert(-[[[[[]]]]] === 0);
-  assert(+[[[[[42]]]]] === 42);
-  assert(-[[[[[42]]]]] === -42);
-  assert(+"" === 0);
-  assert(-"" === 0);
-  assert(+"42" === 42);
-  assert(-"42" === -42);
-  assert(+42 === 42);
-  assert(-42 === -42);
-  assert(+1.23 === 1.23);
-  assert(-1.23 === -1.23);
-  assert(+"1.23" === 1.23);
-  assert(-"1.23" === -1.23);
-  assert(+"Infinity" === Infinity);
-  assert(+"+Infinity" === Infinity);
-  assert(+"-Infinity" === -Infinity);
-  assert(-"Infinity" === -Infinity);
-  assert(-"+Infinity" === -Infinity);
-  assert(-"-Infinity" === Infinity);
-  assert(+"  \r  \t \n " === 0);
-  assert(+"  \n  \t    Infinity   \r   " === Infinity);
-  assert(+"\r     \n1.23   \t\t\t  \n" === 1.23);
-
-  assert(isNaN(+undefined));
-  assert(isNaN(-undefined));
-  assert(isNaN(+{}));
-  assert(isNaN(-{}));
-  assert(isNaN(+{ a: 1 }));
-  assert(isNaN(-{ a: 1 }));
-  assert(isNaN(+[, , ,]));
-  assert(isNaN(-[, , ,]));
-  assert(isNaN(+[undefined, undefined]));
-  assert(isNaN(-[undefined, undefined]));
-  assert(isNaN(+[1, 2, 3]));
-  assert(isNaN(-[1, 2, 3]));
-  assert(isNaN(+[[[["foo"]]]]));
-  assert(isNaN(-[[[["foo"]]]]));
-  assert(isNaN(+"foo"));
-  assert(isNaN(-"foo"));
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+test("non-numeric primitives", () => {
+  expect(+false).toBe(0);
+  expect(-false).toBe(-0);
+  expect(+true).toBe(1);
+  expect(-true).toBe(-1);
+  expect(+null).toBe(0);
+  expect(-null).toBe(-0);
+  expect(+undefined).toBeNaN();
+  expect(-undefined).toBeNaN();
+});
+
+test("arrays", () => {
+  expect(+[]).toBe(0);
+  expect(-[]).toBe(-0);
+  expect(+[,]).toBe(0);
+  expect(-[,]).toBe(-0);
+  expect(+[null]).toBe(0);
+  expect(-[null]).toBe(-0);
+  expect(+[undefined]).toBe(0);
+  expect(-[undefined]).toBe(-0);
+  expect(+[[[[[]]]]]).toBe(0);
+  expect(-[[[[[]]]]]).toBe(-0);
+  expect(+[[[[[42]]]]]).toBe(42);
+  expect(-[[[[[42]]]]]).toBe(-42);
+
+  expect(+[, , ,]).toBeNaN();
+  expect(-[, , ,]).toBeNaN();
+  expect(+[undefined, undefined]).toBeNaN();
+  expect(-[undefined, undefined]).toBeNaN();
+  expect(+[1, 2, 3]).toBeNaN();
+  expect(-[1, 2, 3]).toBeNaN();
+  expect(+[[[["foo"]]]]).toBeNaN();
+  expect(-[[[["foo"]]]]).toBeNaN();
+});
+
+test("strings", () => {
+  expect(+"").toBe(0);
+  expect(-"").toBe(-0);
+  expect(+"42").toBe(42);
+  expect(-"42").toBe(-42);
+  expect(+"1.23").toBe(1.23);
+  expect(-"1.23").toBe(-1.23);
+
+  expect(+"foo").toBeNaN();
+  expect(-"foo").toBeNaN();
+});
+
+test("numbers", () => {
+  expect(+42).toBe(42);
+  expect(-42).toBe(-42);
+  expect(+1.23).toBe(1.23);
+  expect(-1.23).toBe(-1.23);
+});
+
+test("infinity", () => {
+  expect(+"Infinity").toBe(Infinity);
+  expect(+"+Infinity").toBe(Infinity);
+  expect(+"-Infinity").toBe(-Infinity);
+  expect(-"Infinity").toBe(-Infinity);
+  expect(-"+Infinity").toBe(-Infinity);
+  expect(-"-Infinity").toBe(Infinity);
+});
+
+test("space and space-like escapes", () => {
+  expect(+"  \r  \t \n ").toBe(0);
+  expect(+"  \n  \t    Infinity   \r   ").toBe(Infinity);
+  expect(+"\r     \n1.23   \t\t\t  \n").toBe(1.23);
+});
+
+test("object literals", () => {
+  expect(+{}).toBeNaN();
+  expect(-{}).toBeNaN();
+  expect(+{ a: 1 }).toBeNaN();
+  expect(-{ a: 1 }).toBeNaN();
+});
diff --git a/Libraries/LibJS/Tests/to-number-exception.js b/Libraries/LibJS/Tests/to-number-exception.js
index 3eed7253f6..1174ed195d 100644
--- a/Libraries/LibJS/Tests/to-number-exception.js
+++ b/Libraries/LibJS/Tests/to-number-exception.js
@@ -1,54 +1,25 @@
-load("test-common.js");
+const message = "oops, Value::to_number() failed";
 
-try {
-  const message = "oops, Value::to_number() failed";
-  const o = {
-    toString() {
-      throw new Error(message);
-    },
-  };
+const o = {
+  toString() {
+    throw new Error(message);
+  },
+};
 
-  assertThrowsError(
-    () => {
-      +o;
-    },
-    {
-      error: Error,
-      message,
-    }
-  );
+test("basic functionality", () => {
+  expect(() => {
+    +o;
+  }).toThrowWithMessage(Error, message);
 
-  assertThrowsError(
-    () => {
-      o - 1;
-    },
-    {
-      error: Error,
-      message,
-    }
-  );
+  expect(() => {
+    o - 1;
+  }).toThrowWithMessage(Error, message);
 
-  assertThrowsError(
-    () => {
-      "foo".charAt(o);
-    },
-    {
-      error: Error,
-      message,
-    }
-  );
+  expect(() => {
+    "foo".charAt(o);
+  }).toThrowWithMessage(Error, message);
 
-  assertThrowsError(
-    () => {
-      "bar".repeat(o);
-    },
-    {
-      error: Error,
-      message,
-    }
-  );
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+  expect(() => {
+    "bar".repeat(o);
+  }).toThrowWithMessage(Error, message);
+});
diff --git a/Libraries/LibJS/Tests/update-expression-on-member-expression.js b/Libraries/LibJS/Tests/update-expression-on-member-expression.js
index 3ddb8a1869..f24e76ee51 100644
--- a/Libraries/LibJS/Tests/update-expression-on-member-expression.js
+++ b/Libraries/LibJS/Tests/update-expression-on-member-expression.js
@@ -1,5 +1,5 @@
 test("basic update expression", () => {
-  var o = {};
+  const o = {};
   o.f = 1;
 
   expect(o.f++).toBe(1);
diff --git a/Libraries/LibJS/Tests/update-expressions-basic.js b/Libraries/LibJS/Tests/update-expressions-basic.js
index 32add75d2e..160819b260 100644
--- a/Libraries/LibJS/Tests/update-expressions-basic.js
+++ b/Libraries/LibJS/Tests/update-expressions-basic.js
@@ -1,57 +1,53 @@
-load("test-common.js");
-
-try {
-  assertThrowsError(
-    () => {
+describe("correct behavior", () => {
+  test("basic functionality", () => {
+    let n = 0;
+    expect(++n).toBe(1);
+    expect(n).toBe(1);
+
+    n = 0;
+    expect(n++).toBe(0);
+    expect(n).toBe(1);
+
+    n = 0;
+    expect(--n).toBe(-1);
+    expect(n).toBe(-1);
+
+    n = 0;
+    expect(n--).toBe(0);
+    expect(n).toBe(-1);
+
+    let a = [];
+    expect(a++).toBe(0);
+    expect(a).toBe(1);
+
+    let b = true;
+    expect(b--).toBe(1);
+    expect(b).toBe(0);
+  });
+
+  test("updates that produce NaN", () => {
+    let s = "foo";
+    expect(++s).toBeNaN();
+    expect(s).toBeNaN();
+
+    s = "foo";
+    expect(s++).toBeNaN();
+    expect(s).toBeNaN();
+
+    s = "foo";
+    expect(--s).toBeNaN();
+    expect(s).toBeNaN();
+
+    s = "foo";
+    expect(s--).toBeNaN();
+    expect(s).toBeNaN();
+  });
+});
+
+describe("errors", () => {
+  test("update expression throws reference error", () => {
+    expect(() => {
       ++x;
-    },
-    {
-      error: ReferenceError,
-      message: "'x' is not defined",
-    }
-  );
-
-  var n = 0;
-  assert(++n === 1);
-  assert(n === 1);
-
-  var n = 0;
-  assert(n++ === 0);
-  assert(n === 1);
-
-  var n = 0;
-  assert(--n === -1);
-  assert(n === -1);
-
-  var n = 0;
-  assert(n-- === 0);
-  assert(n === -1);
-
-  var a = [];
-  assert(a++ === 0);
-  assert(a === 1);
-
-  var b = true;
-  assert(b-- === 1);
-  assert(b === 0);
-
-  var s = "foo";
-  assert(isNaN(++s));
-  assert(isNaN(s));
-
-  var s = "foo";
-  assert(isNaN(s++));
-  assert(isNaN(s));
-
-  var s = "foo";
-  assert(isNaN(--s));
-  assert(isNaN(s));
-
-  var s = "foo";
-  assert(isNaN(s--));
-  assert(isNaN(s));
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+    }).toThrowWithMessage(ReferenceError, "'x' is not defined");
+  });
+});
diff --git a/Libraries/LibJS/Tests/var-multiple-declarator.js b/Libraries/LibJS/Tests/var-multiple-declarator.js
index 0596f4057c..089e67313c 100644
--- a/Libraries/LibJS/Tests/var-multiple-declarator.js
+++ b/Libraries/LibJS/Tests/var-multiple-declarator.js
@@ -1,13 +1,8 @@
-load("test-common.js");
-
-try {
+test("basic functionality", () => {
   var a = 1,
     b = 2,
     c = a + b;
-  assert(a === 1);
-  assert(b === 2);
-  assert(c === 3);
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+  expect(a).toBe(1);
+  expect(b).toBe(2);
+  expect(c).toBe(3);
+});
diff --git a/Libraries/LibJS/Tests/var-scoping.js b/Libraries/LibJS/Tests/var-scoping.js
index 44cb2af741..478836a43e 100644
--- a/Libraries/LibJS/Tests/var-scoping.js
+++ b/Libraries/LibJS/Tests/var-scoping.js
@@ -1,9 +1,7 @@
-load("test-common.js");
-
-try {
+test("basic functionality", () => {
   function foo() {
     i = 3;
-    assert(i === 3);
+    expect(i).toBe(3);
     var i;
   }
 
@@ -15,9 +13,5 @@ try {
   } catch (e) {
     caught_exception = e;
   }
-  assert(caught_exception !== undefined);
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+  expect(caught_exception).not.toBeUndefined();
+});
diff --git a/Libraries/LibJS/Tests/variable-declaration.js b/Libraries/LibJS/Tests/variable-declaration.js
deleted file mode 100644
index 7a6c0b85b3..0000000000
--- a/Libraries/LibJS/Tests/variable-declaration.js
+++ /dev/null
@@ -1,27 +0,0 @@
-load("test-common.js");
-
-try {
-  const constantValue = 1;
-  assertThrowsError(
-    () => {
-      constantValue = 2;
-    },
-    {
-      error: TypeError,
-      message: "Invalid assignment to const variable",
-    }
-  );
-  assert(constantValue === 1);
-
-  // Make sure we can define new constants in inner scopes.
-  const constantValue2 = 1;
-  do {
-    const constantValue2 = 2;
-    assert(constantValue2 === 2);
-  } while (false);
-  assert(constantValue2 === 1);
-
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
diff --git a/Libraries/LibJS/Tests/variable-undefined.js b/Libraries/LibJS/Tests/variable-undefined.js
index c853a3e8c2..d9963feaee 100644
--- a/Libraries/LibJS/Tests/variable-undefined.js
+++ b/Libraries/LibJS/Tests/variable-undefined.js
@@ -1,19 +1,14 @@
-load("test-common.js");
+test("basic functionality", () => {
+  function foo(a) {
+    return a;
+  }
 
-function foo(a) {
-  return a;
-}
-
-try {
   var x = undefined;
-  assert(x === undefined);
-  assert(foo(x) === undefined);
+  expect(x).toBeUndefined();
+  expect(foo(x)).toBeUndefined();
 
   var o = {};
   o.x = x;
-  assert(o.x === undefined);
-  assert(o.x === x);
-  console.log("PASS");
-} catch (e) {
-  console.log("FAIL: " + e);
-}
+  expect(o.x).toBeUndefined();
+  expect(o.x).toBe(x);
+});