LibJS: Implement Temporal.Duration.prototype.negated()

Userland/Libraries/LibJS/Tests/builtins/Temporal/Duration/Duration.prototype.negated.js

@@ -0,0 +1,42 @@
+const DURATION_PROPERTIES = [
+    "years",
+    "months",
+    "weeks",
+    "days",
+    "hours",
+    "minutes",
+    "seconds",
+    "milliseconds",
+    "microseconds",
+    "nanoseconds",
+];
+
+describe("correct behavior", () => {
+    test("length is 0", () => {
+        expect(Temporal.Duration.prototype.negated).toHaveLength(0);
+    });
+
+    test("basic functionality", () => {
+        const negativeDuration = new Temporal.Duration(123).negated();
+        expect(negativeDuration.years).toBe(-123);
+
+        const positiveDuration = new Temporal.Duration(-123).negated();
+        expect(positiveDuration.years).toBe(123);
+    });
+
+    test("each property is negated", () => {
+        const values = Array(DURATION_PROPERTIES.length).fill(1);
+        const duration = new Temporal.Duration(...values).negated();
+        for (const property of DURATION_PROPERTIES) {
+            expect(duration[property]).toBe(-1);
+        }
+    });
+});
+
+test("errors", () => {
+    test("this value must be a Temporal.Duration object", () => {
+        expect(() => {
+            Temporal.Duration.prototype.negated.call("foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.Duration");
+    });
+});