LibJS: Implement AggregateError

Userland/Libraries/LibJS/Tests/builtins/AggregateError/AggregateError.js

@@ -0,0 +1,59 @@
+describe("errors", () => {
+    test("first argument must be coercible to object", () => {
+        expect(() => {
+            new AggregateError();
+        }).toThrowWithMessage(TypeError, "ToObject on null or undefined");
+    });
+
+    test("@@iterator throws", () => {
+        expect(() => {
+            new AggregateError({
+                [Symbol.iterator]() {
+                    throw Error("oops!");
+                },
+            });
+        }).toThrowWithMessage(Error, "oops!");
+    });
+});
+
+describe("normal behavior", () => {
+    test("length is 2", () => {
+        expect(AggregateError).toHaveLength(2);
+    });
+
+    test("name is AggregateError", () => {
+        expect(AggregateError.name).toBe("AggregateError");
+    });
+
+    test("Prototype of the AggregateError constructor is the Error constructor", () => {
+        expect(Object.getPrototypeOf(AggregateError)).toBe(Error);
+    });
+
+    test("Prototype of AggregateError.prototype is Error.prototype", () => {
+        expect(Object.getPrototypeOf(AggregateError.prototype)).toBe(Error.prototype);
+    });
+
+    test("basic functionality", () => {
+        expect(AggregateError([])).toBeInstanceOf(AggregateError);
+        expect(new AggregateError([])).toBeInstanceOf(AggregateError);
+        expect(new AggregateError([]).toString()).toBe("AggregateError");
+        expect(new AggregateError([], "Foo").toString()).toBe("AggregateError: Foo");
+        expect(new AggregateError([]).hasOwnProperty("errors")).toBeTrue();
+        const errors = [1, 2, 3];
+        expect(new AggregateError(errors).errors).toEqual(errors);
+        expect(new AggregateError(errors).errors).not.toBe(errors);
+        expect(
+            new AggregateError({
+                [Symbol.iterator]: (i = 0) => ({
+                    next() {
+                        if (i < 3) {
+                            i++;
+                            return { value: i };
+                        }
+                        return { value: null, done: true };
+                    },
+                }),
+            }).errors
+        ).toEqual(errors);
+    });
+});