LibJS: Implement Date.prototype.setUTCMilliseconds

Userland/Libraries/LibJS/Tests/builtins/Date/Date.prototype.setUTCMilliseconds.js

@@ -0,0 +1,38 @@
+describe("errors", () => {
+    test("called on non-Date object", () => {
+        expect(() => {
+            Date.prototype.setUTCMilliseconds();
+        }).toThrowWithMessage(TypeError, "Not an object of type Date");
+    });
+
+    test("called with non-numeric parameters", () => {
+        expect(() => {
+            new Date().setUTCMilliseconds(Symbol.hasInstance);
+        }).toThrowWithMessage(TypeError, "Cannot convert symbol to number");
+    });
+});
+
+describe("correct behavior", () => {
+    const d = new Date(2000, 2, 1);
+
+    test("basic functionality", () => {
+        d.setUTCMilliseconds(8);
+        expect(d.getUTCMilliseconds()).toBe(8);
+
+        d.setUTCMilliseconds("");
+        expect(d.getUTCMilliseconds()).toBe(0);
+
+        d.setUTCMilliseconds("a");
+        expect(d.getUTCMilliseconds()).toBe(NaN);
+    });
+
+    test("NaN", () => {
+        d.setUTCMilliseconds(NaN);
+        expect(d.getUTCMilliseconds()).toBeNaN();
+    });
+
+    test("time clip", () => {
+        d.setUTCMilliseconds(8.65e15);
+        expect(d.getUTCMilliseconds()).toBeNaN();
+    });
+});