1 files changed, 67 insertions, 0 deletions
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Object/Object.preventExtensions.js b/Userland/Libraries/LibJS/Tests/builtins/Object/Object.preventExtensions.js
new file mode 100644
index 0000000000..292c3f5999
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Object/Object.preventExtensions.js
@@ -0,0 +1,67 @@
+describe("correct behavior", () => {
+    test("non-object arguments", () => {
+        expect(Object.preventExtensions()).toBeUndefined();
+        expect(Object.preventExtensions(undefined)).toBeUndefined();
+        expect(Object.preventExtensions(null)).toBeNull();
+        expect(Object.preventExtensions(true)).toBeTrue();
+        expect(Object.preventExtensions(6)).toBe(6);
+        expect(Object.preventExtensions("test")).toBe("test");
+
+        let s = Symbol();
+        expect(Object.preventExtensions(s)).toBe(s);
+    });
+
+    test("basic functionality", () => {
+        let o = { foo: "foo" };
+        expect(o.foo).toBe("foo");
+        o.bar = "bar";
+        expect(o.bar).toBe("bar");
+
+        expect(Object.preventExtensions(o)).toBe(o);
+        expect(o.foo).toBe("foo");
+        expect(o.bar).toBe("bar");
+
+        o.baz = "baz";
+        expect(o.baz).toBeUndefined();
+    });
+
+    test("modifying existing properties", () => {
+        const o = { foo: "bar" };
+        Object.preventExtensions(o);
+        o.foo = "baz";
+        expect(o.foo).toBe("baz");
+    });
+
+    test("deleting existing properties", () => {
+        const o = { foo: "bar" };
+        Object.preventExtensions(o);
+        delete o.foo;
+        expect(o).not.toHaveProperty("foo");
+    });
+});
+
+describe("errors", () => {
+    test("defining a property on a non-extensible object", () => {
+        let o = {};
+        Object.preventExtensions(o);
+
+        expect(() => {
+            Object.defineProperty(o, "baz", { value: "baz" });
+        }).toThrowWithMessage(TypeError, "Cannot define property baz on non-extensible object");
+
+        expect(o.baz).toBeUndefined();
+    });
+
+    test("putting property on a non-extensible object", () => {
+        let o = {};
+        Object.preventExtensions(o);
+
+        expect(() => {
+            "use strict";
+            o.foo = "foo";
+        }).toThrowWithMessage(TypeError, "Cannot define property foo on non-extensible object");
+
+        expect((o.foo = "foo")).toBe("foo");
+        expect(o.foo).toBeUndefined();
+    });
+});