LibJS: Add all of the WeakMap.prototype methods (delete, get, has, set)

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

@@ -0,0 +1,34 @@
+test("constructor properties", () => {
+    expect(WeakMap).toHaveLength(0);
+    expect(WeakMap.name).toBe("WeakMap");
+});
+
+describe("errors", () => {
+    test("invalid array iterators", () => {
+        [-100, Infinity, NaN, {}, 152n].forEach(value => {
+            expect(() => {
+                new WeakMap(value);
+            }).toThrowWithMessage(TypeError, "is not iterable");
+        });
+    });
+    test("called without new", () => {
+        expect(() => {
+            WeakMap();
+        }).toThrowWithMessage(TypeError, "WeakMap constructor must be called with 'new'");
+    });
+});
+
+describe("normal behavior", () => {
+    test("typeof", () => {
+        expect(typeof new WeakMap()).toBe("object");
+    });
+
+    test("constructor with single array of entries argument", () => {
+        var a = new WeakMap([
+            [{ a: 1 }, 1],
+            [{ a: 2 }, 2],
+            [{ a: 3 }, 3],
+        ]);
+        expect(a instanceof WeakMap).toBeTrue();
+    });
+});