Add tests for isOdd snippet

test/isOdd.test.js

@@ -0,0 +1,11 @@
+const {isOdd} = require('./_30s.js');
+
+test('isOdd is a Function', () => {
+  expect(isOdd).toBeInstanceOf(Function);
+});
+test('4 is not an odd number', () => {
+  expect(isOdd(4)).toBeFalsy();
+});
+test('5 is an odd number', () => {
+  expect(isOdd(5)).toBeTruthy();
+});