Libraries: Move to Userland/Libraries/

Userland/Libraries/LibJS/Tests/update-expressions-basic.js

@@ -0,0 +1,53 @@
+describe("correct behavior", () => {
+    test("basic functionality", () => {
+        let n = 0;
+        expect(++n).toBe(1);
+        expect(n).toBe(1);
+
+        n = 0;
+        expect(n++).toBe(0);
+        expect(n).toBe(1);
+
+        n = 0;
+        expect(--n).toBe(-1);
+        expect(n).toBe(-1);
+
+        n = 0;
+        expect(n--).toBe(0);
+        expect(n).toBe(-1);
+
+        let a = [];
+        expect(a++).toBe(0);
+        expect(a).toBe(1);
+
+        let b = true;
+        expect(b--).toBe(1);
+        expect(b).toBe(0);
+    });
+
+    test("updates that produce NaN", () => {
+        let s = "foo";
+        expect(++s).toBeNaN();
+        expect(s).toBeNaN();
+
+        s = "foo";
+        expect(s++).toBeNaN();
+        expect(s).toBeNaN();
+
+        s = "foo";
+        expect(--s).toBeNaN();
+        expect(s).toBeNaN();
+
+        s = "foo";
+        expect(s--).toBeNaN();
+        expect(s).toBeNaN();
+    });
+});
+
+describe("errors", () => {
+    test("update expression throws reference error", () => {
+        expect(() => {
+            ++x;
+        }).toThrowWithMessage(ReferenceError, "'x' is not defined");
+    });
+});