merge: Add MinHeap and test (#817)

* Add MinHeap and test

* Add description and reference link

* Adjust formatting

Data-Structures/Heap/test/MinHeap.test.js

@@ -0,0 +1,33 @@
+import { MinHeap } from '../MinHeap'
+
+describe('MinHeap', () => {
+  const array = [2, 4, 10, 23, 43, 42, 39, 7, 9, 16, 85, 1, 51]
+  let heap
+
+  beforeEach(() => {
+    heap = new MinHeap(array)
+  })
+
+  it('should initialize a heap from an input array', () => {
+    expect(heap).toEqual({ 'heap': [1, 4, 2, 7, 16, 10, 39, 23, 9, 43, 85, 42, 51] })   // eslint-disable-line
+  })
+
+  it('should show the top value in the heap', () => {
+    const minValue = heap.peek()
+
+    expect(minValue).toEqual(1)
+  })
+
+  it('should remove and return the top value in the heap', () => {
+    const minValue = heap.extractMin()
+
+    expect(minValue).toEqual(1)
+    expect(heap).toEqual({ 'heap': [2, 4, 10, 7, 16, 42, 39, 23, 9, 43, 85, 51] })      // eslint-disable-line
+  })
+
+  it('should insert a new value and sort until it meets heap conditions', () => {
+    heap.insert(15)
+
+    expect(heap).toEqual({ 'heap': [2, 4, 10, 7, 16, 15, 39, 23, 9, 43, 85, 51, 42] })  // eslint-disable-line
+  })
+})