added unit tests

Author: rafalpiotrowski

src/BitUtil.ts

@@ -299,7 +299,7 @@ export class BitUtil {
      * @return true if the number is a positive power of 2, otherwise false.
      */
     public static isPowerOfTwo(value: number): boolean {
-        return value > 0 && (value & -value) === value;
+        return value > 0 && (value & (~value + 1)) === value;
     }
 
     /**
@@ -309,7 +309,7 @@ export class BitUtil {
      * @return true if the number is a positive power of 2, otherwise false.
      */
     public static isPowerOfTwoBigInt(value: bigint): boolean {
-        return value > BigInt(0) && (value & -value) === value;
+        return value > 0n && (value & (~value + 1n)) === value;
     }
 
     /**

tests/BitUtil.test.ts

@@ -0,0 +1,94 @@
+import { BitUtil } from "../src/index";
+
+describe("isEven", () => {
+    test("check if number is even", () => {
+        expect(BitUtil.isEven(0)).toBe(true);
+        expect(BitUtil.isEven(1)).toBe(false);
+    });
+});
+
+describe("previous", () => {
+    test("should produce current - 1 or max - 1 if 0", () => {
+        expect(BitUtil.previous(0, 10)).toBe(9);
+        expect(BitUtil.previous(1, 10)).toBe(0);
+        expect(BitUtil.previous(2, 10)).toBe(1);
+    });
+});
+
+describe("next", () => {
+    test("should produce current + 1 or 0 if max - 1", () => {
+        expect(BitUtil.next(0, 10)).toBe(1);
+        expect(BitUtil.next(1, 10)).toBe(2);
+        expect(BitUtil.next(9, 10)).toBe(0);
+    });
+});
+
+describe("isPowerOfTwo", () => {
+    test("should return true for positive powers of 2", () => {
+        expect(BitUtil.isPowerOfTwo(1)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(2)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(4)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(8)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(16)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(32)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(64)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(128)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(256)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(512)).toBe(true);
+        expect(BitUtil.isPowerOfTwo(1024)).toBe(true);
+    });
+
+    test("should return false for non-positive numbers", () => {
+        expect(BitUtil.isPowerOfTwo(0)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(-1)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(-2)).toBe(false);
+    });
+
+    test("should return false for non-power of 2 numbers", () => {
+        expect(BitUtil.isPowerOfTwo(3)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(5)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(6)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(7)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(9)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(10)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(12)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(15)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(18)).toBe(false);
+        expect(BitUtil.isPowerOfTwo(20)).toBe(false);
+    });
+});
+
+describe("isPowerOfTwoBigInt", () => {
+    test("should return true for positive powers of 2", () => {
+        expect(BitUtil.isPowerOfTwoBigInt(1n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(2n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(4n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(8n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(16n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(32n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(64n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(128n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(256n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(512n)).toBe(true);
+        expect(BitUtil.isPowerOfTwoBigInt(1024n)).toBe(true);
+    });
+
+    test("should return false for non-positive numbers", () => {
+        expect(BitUtil.isPowerOfTwoBigInt(0n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(-1n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(-2n)).toBe(false);
+    });
+
+    test("should return false for non-power of 2 numbers", () => {
+        expect(BitUtil.isPowerOfTwoBigInt(3n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(5n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(6n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(7n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(9n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(10n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(12n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(15n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(18n)).toBe(false);
+        expect(BitUtil.isPowerOfTwoBigInt(20n)).toBe(false);
+    });
+});