Add more tests to isPositive() bitwise function.

Author: trekhleb

src/algorithms/math/bits/README.md

@@ -53,23 +53,16 @@ isEven: true
 
 #### isPositive
 
-This method determines if the number provided is positive.
-It is based on the fact that all positive numbers have their last
-left bit to be set to 0. However, if the number provided is zero
-or negative zero, it should still return false.
+This method determines if the number is positive. It is based on the fact that all positive 
+numbers have their leftmost bit to be set to `0`. However, if the number provided is zero
+or negative zero, it should still return `false`.
 
 ```text
 Number: 1 = 0b0001
 isPositive: true
 
 Number: -1 = -0b0001
 isPositive: false
-
-Number: 0 = 0b0000
-isPositive: false
-
-Number: -0 = 0b0000
-isPositive: false
 ```
 
 > See [isPositive.js](isPositive.js) for further details.

src/algorithms/math/bits/__test__/isPositive.test.js

@@ -2,9 +2,18 @@ import isPositive from '../isPositive';
 
 describe('isPositive', () => {
   it('should detect if a number is positive', () => {
+    expect(isPositive(1)).toBe(true);
+    expect(isPositive(2)).toBe(true);
+    expect(isPositive(3)).toBe(true);
+    expect(isPositive(5665)).toBe(true);
+    expect(isPositive(56644325)).toBe(true);
+
     expect(isPositive(0)).toBe(false);
     expect(isPositive(-0)).toBe(false);
-    expect(isPositive(1)).toBe(true);
     expect(isPositive(-1)).toBe(false);
+    expect(isPositive(-2)).toBe(false);
+    expect(isPositive(-126)).toBe(false);
+    expect(isPositive(-5665)).toBe(false);
+    expect(isPositive(-56644325)).toBe(false);
   });
 });

src/algorithms/math/bits/isPositive.js

@@ -1,13 +1,13 @@
 /**
- * @param {number} number
+ * @param {number} number - 32-bit integer.
  * @return {boolean}
  */
 export default function isPositive(number) {
-  // Zero is neither a positive nor a negative number
+  // Zero is neither a positive nor a negative number.
   if (number === 0) {
     return false;
   }
 
-  // The most signification bit can be used to determine whether .
+  // The most significant 32nd bit can be used to determine whether the number is positive.
   return ((number >> 31) & 1) === 0;
 }