LibJS: Implement Atomics.isLockFree

Author: https://github.com/trflynn89
Commit: 1a3e1bff7b
Pull-request: https://github.com/SerenityOS/serenity/pull/8752
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Tests/builtins/Atomics/Atomics.isLockFree.js

@@ -0,0 +1,25 @@
+test("invariants", () => {
+    expect(Atomics.isLockFree).toHaveLength(1);
+});
+
+test("basic functionality", () => {
+    expect(Atomics.isLockFree(4)).toBeTrue();
+
+    // Can't assume the return value of sizes 1, 2, and 8, but they shouldn't change.
+    expect(Atomics.isLockFree(1)).toBe(Atomics.isLockFree(1));
+    expect(Atomics.isLockFree(2)).toBe(Atomics.isLockFree(2));
+    expect(Atomics.isLockFree(8)).toBe(Atomics.isLockFree(8));
+
+    expect(Atomics.isLockFree(0)).toBeFalse();
+    expect(Atomics.isLockFree(3)).toBeFalse();
+    expect(Atomics.isLockFree(5)).toBeFalse();
+    expect(Atomics.isLockFree(6)).toBeFalse();
+    expect(Atomics.isLockFree(7)).toBeFalse();
+    expect(Atomics.isLockFree(9)).toBeFalse();
+    expect(Atomics.isLockFree(10)).toBeFalse();
+    expect(Atomics.isLockFree(Infinity)).toBeFalse();
+
+    expect(Atomics.isLockFree("not a number")).toBeFalse();
+    expect(Atomics.isLockFree(new Float32Array(4))).toBeFalse();
+    expect(Atomics.isLockFree(String.prototype)).toBeFalse();
+});