Don't treat 1 as prime number.

Author: trekhleb

src/algorithms/math/primality-test/__test__/trialDivision.test.js

@@ -4,7 +4,7 @@ import trialDivision from '../trialDivision';
  * @param {function(n: number)} testFunction
  */
 function primalityTest(testFunction) {
-  expect(testFunction(1)).toBeTruthy();
+  expect(testFunction(1)).toBeFalsy();
   expect(testFunction(2)).toBeTruthy();
   expect(testFunction(3)).toBeTruthy();
   expect(testFunction(5)).toBeTruthy();

src/algorithms/math/primality-test/trialDivision.js

@@ -3,11 +3,11 @@
  * @return {boolean}
  */
 export default function trialDivision(number) {
-  if (number <= 0) {
-    // If number is less then one then it isn't prime by definition.
+  if (number <= 1) {
+    // If number is less than one then it isn't prime by definition.
     return false;
   } else if (number <= 3) {
-    // All numbers from 1 to 3 are prime.
+    // All numbers from 2 to 3 are prime.
     return true;
   }