LibJS: Implement Date.prototype.setUTCMonth

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

@@ -0,0 +1,46 @@
+describe("errors", () => {
+    test("called on non-Date object", () => {
+        expect(() => {
+            Date.prototype.setUTCMonth();
+        }).toThrowWithMessage(TypeError, "Not an object of type Date");
+    });
+
+    test("called with non-numeric parameters", () => {
+        expect(() => {
+            new Date().setUTCMonth(Symbol.hasInstance);
+        }).toThrowWithMessage(TypeError, "Cannot convert symbol to number");
+
+        expect(() => {
+            new Date().setUTCMonth(1989, Symbol.hasInstance);
+        }).toThrowWithMessage(TypeError, "Cannot convert symbol to number");
+    });
+});
+
+describe("correct behavior", () => {
+    const d = new Date(2000, 2, 1);
+
+    test("basic functionality", () => {
+        d.setUTCMonth(8);
+        expect(d.getUTCMonth()).toBe(8);
+
+        d.setUTCMonth(9, 15);
+        expect(d.getUTCMonth()).toBe(9);
+        expect(d.getUTCDate()).toBe(15);
+
+        d.setUTCMonth("");
+        expect(d.getUTCMonth()).toBe(0);
+
+        d.setUTCMonth("a");
+        expect(d.getUTCMonth()).toBe(NaN);
+    });
+
+    test("NaN", () => {
+        d.setUTCMonth(NaN);
+        expect(d.getUTCMonth()).toBeNaN();
+    });
+
+    test("time clip", () => {
+        d.setUTCMonth(8.65e15);
+        expect(d.getUTCMonth()).toBeNaN();
+    });
+});