LibJS: Reorganize tests into subfolders

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

@@ -0,0 +1,66 @@
+load("test-common.js");
+
+try {
+    assert((new Proxy({}, { set: undefined }).foo = 1) === 1);
+    assert((new Proxy({}, { set: null }).foo = 1) === 1);
+    assert((new Proxy({}, {}).foo = 1) === 1);
+
+    let o = {};
+    let p = new Proxy(o, {
+        set(target, prop, value, receiver) {
+            assert(target === o);
+            assert(prop === "foo");
+            assert(value === 10);
+            assert(receiver === p);
+            return true;
+        },
+    });
+
+    p.foo = 10;
+
+    p = new Proxy(o, {
+        set(target, prop, value, receiver) {
+            if (target[prop] === value) {
+                target[prop] *= 2;
+            } else {
+                target[prop] = value;
+            }
+        },
+    });
+
+    p.foo = 10;
+    assert(p.foo === 10);
+    p.foo = 10;
+    assert(p.foo === 20);
+    p.foo = 10;
+    assert(p.foo === 10);
+
+    // Invariants
+
+    o = {};
+    Object.defineProperty(o, "foo", { value: 10 });
+    p = new Proxy(o, {
+        set() {
+            return true;
+        },
+    });
+
+    assertThrowsError(() => {
+        p.foo = 12;
+    }, {
+        error: TypeError,
+        message: "Proxy handler's set trap violates invariant: cannot return true for a property on the target which is a non-configurable, non-writable own data property",
+    });
+
+    Object.defineProperty(o, "bar", { get() {} });
+    assertThrowsError(() => {
+        p.bar = 12;
+    }, {
+        error: TypeError,
+        message: "Proxy handler's set trap violates invariant: cannot return true for a property on the target which is a non-configurable own accessor property with an undefined set attribute",
+    });
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}