Everywhere: Hoist the Libraries folder to the top-level

Author: https://github.com/trflynn89
Commit: 93712b24bf
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2256
Reviewed-by: https://github.com/sideshowbarker

Libraries/LibJS/Tests/builtins/Proxy/Proxy.handler-isExtensible.js

@@ -0,0 +1,39 @@
+describe("[[IsExtensible]] trap normal behavior", () => {
+    test("forwarding when not defined in handler", () => {
+        expect(Object.isExtensible(new Proxy({}, { isExtensible: null }))).toBeTrue();
+        expect(Object.isExtensible(new Proxy({}, { isExtensible: undefined }))).toBeTrue();
+        expect(Object.isExtensible(new Proxy({}, {}))).toBeTrue();
+    });
+
+    test("correct arguments supplied to trap", () => {
+        let o = {};
+        let p = new Proxy(o, {
+            isExtensible(target) {
+                expect(target).toBe(o);
+                return true;
+            },
+        });
+
+        expect(Object.isExtensible(p)).toBeTrue();
+    });
+});
+
+describe("[[Call]] invariants", () => {
+    test("return value must match the target's extensibility", () => {
+        let o = {};
+        Object.preventExtensions(o);
+
+        let p = new Proxy(o, {
+            isExtensible() {
+                return true;
+            },
+        });
+
+        expect(() => {
+            Object.isExtensible(p);
+        }).toThrowWithMessage(
+            TypeError,
+            "Proxy handler's isExtensible trap violates invariant: return value must match the target's extensibility"
+        );
+    });
+});