LibJS: Add tests for issue #3382

Author: https://github.com/linusg
Commit: 55c4866370
Pull-request: https://github.com/SerenityOS/serenity/pull/3383
Reviewed-by: https://github.com/awesomekling

Libraries/LibJS/Tests/builtins/Array/array-simple-and-generic-storage-initialization.js

@@ -0,0 +1,15 @@
+describe("Issue #3382", () => {
+    test("Creating an array with simple storage (<= 200 initial elements)", () => {
+        var a = Array(200);
+        expect(a).toHaveLength(200);
+        expect(a.push("foo")).toBe(201);
+        expect(a).toHaveLength(201);
+    });
+
+    test("Creating an array with generic storage (> 200 initial elements)", () => {
+        var a = Array(201);
+        expect(a).toHaveLength(201);
+        expect(a.push("foo")).toBe(202);
+        expect(a).toHaveLength(202);
+    });
+});