tests: Project Euler Problem 2 (#1200)

DIRECTORY.md

@@ -268,6 +268,7 @@
 * **Sorts**
   * [AlphaNumericalSort](Sorts/AlphaNumericalSort.js)
   * [BeadSort](Sorts/BeadSort.js)
+  * [BinaryInsertionSort](Sorts/BinaryInsertionSort.js)
   * [BogoSort](Sorts/BogoSort.js)
   * [BubbleSort](Sorts/BubbleSort.js)
   * [BucketSort](Sorts/BucketSort.js)

Project-Euler/Problem002.js

@@ -5,8 +5,10 @@ const PHI = (1 + SQ5) / 2 // definition of PHI
 // theoretically it should take O(1) constant amount of time as long
 // arithmetic calculations are considered to be in constant amount of time
 export const EvenFibonacci = (limit) => {
+  if (limit < 1) throw new Error('Fibonacci sequence limit can\'t be less than 1')
+
   const highestIndex = Math.floor(Math.log(limit * SQ5) / Math.log(PHI))
   const n = Math.floor(highestIndex / 3)
-  return ((PHI ** (3 * n + 3) - 1) / (PHI ** 3 - 1) -
+  return Math.floor(((PHI ** (3 * n + 3) - 1) / (PHI ** 3 - 1) -
-    ((1 - PHI) ** (3 * n + 3) - 1) / ((1 - PHI) ** 3 - 1)) / SQ5
+    ((1 - PHI) ** (3 * n + 3) - 1) / ((1 - PHI) ** 3 - 1)) / SQ5)
 }

Project-Euler/test/Problem002.test.js

@@ -0,0 +1,14 @@
+import { EvenFibonacci } from '../Problem002'
+
+describe('Even Fibonacci numbers', () => {
+  it('should throw error when limit is less than 1', () => {
+    expect(() => EvenFibonacci(-1)).toThrowError('Fibonacci sequence limit can\'t be less than 1')
+  })
+  test('when limit is greater than 0', () => {
+    expect(EvenFibonacci(40)).toBe(44)
+  })
+  // Project Euler Condition Check
+  test('when limit is 4 million', () => {
+    expect(EvenFibonacci(4e6)).toBe(4613732)
+  })
+})