test: add IntroSort tests

Sorts/IntroSort.js

@@ -241,69 +241,4 @@ function introsort(array, compare) {
   })(array, compare)
 }
 
-/**
- * @example Demo run of the sort routine
- * The data is randomly generated
- * Returns 'RIGHT:)' if the sort routine worked as expected,
- *         'WRONG!!' otherwise
- */
-function demo1() {
-  const data = []
-  const size = 1000000
-  let i = 0
-  let temp
-  const c = function (a, b) {
-    return a - b
-  }
-  for (i = 0; i < size; i++) {
-    temp = Math.random() * Number.MAX_SAFE_INTEGER
-    data.push(temp)
-  }
-  introsort(data, c)
-  let faulty = false
-  for (i = 1; i < size; i++) {
-    if (data[i] < data[i - 1]) {
-      faulty = true
-      break
-    }
-  }
-  if (faulty) {
-    return 'WRONG!!'
-  } else {
-    return 'RIGHT:)'
-  }
-}
-
-/**
- * @example Demo run of the sort routine
- * using the default compare function and
- * comparing the results with Array.sort
- */
-function demo2() {
-  const data = []
-  const data2 = []
-  const size = 1000000
-  let i = 0
-  let temp
-  for (i = 0; i < size; i++) {
-    temp = Math.random() * Number.MAX_SAFE_INTEGER
-    data.push(temp)
-    data2.push(temp)
-  }
-  introsort(data)
-  data2.sort()
-  let faulty = false
-  for (i = 1; i < size; i++) {
-    if (data[i] !== data2[i]) {
-      faulty = true
-      break
-    }
-  }
-  if (faulty) {
-    return 'WRONG Implemented Comparator!!'
-  } else {
-    return 'Comparator Works Fine:)'
-  }
-}
-
-export { introsort, demo1, demo2 }
+export { introsort }

Sorts/test/IntroSort.test.js

@@ -0,0 +1,74 @@
+import { introsort } from '../IntroSort'
+
+describe('introsort', () => {
+  it('should have a robust default comparator', () => {
+    // toString, null, undefined
+    const mixedData = [undefined, '2', 1, false, null, { a: 7 }]
+    introsort(mixedData)
+    expect(mixedData).toEqual([1, '2', { a: 7 }, false, null, undefined])
+
+    // Symbol
+    expect(() => introsort([Symbol(), Symbol()])).toThrowError()
+  })
+
+  it('fails gracefully', () => {
+    introsort('string')
+    introsort([])
+    introsort(['one len'])
+    introsort([1, 2, 3], 'string')
+  })
+
+  it('should sort randomly generated data', function demo1() {
+    // make array
+    const data = []
+    const size = 10_000
+    for (let i = 0; i < size; i++) {
+      const temp = Math.random() * Number.MAX_SAFE_INTEGER
+      data.push(temp)
+    }
+
+    // custom comparator
+    const c = function (a, b) {
+      return a - b
+    }
+    introsort(data, c)
+
+    // check that all numbers are smaller than the one after them
+    let faulty = false
+    for (let i = 1; i < size; i++) {
+      if (data[i - 1] > data[i]) {
+        faulty = true
+        break
+      }
+    }
+
+    expect(faulty).toEqual(false)
+  })
+
+  it('should match the sorting of Array.sort()', function demo2() {
+    // make arrays
+    const data = []
+    const data2 = []
+    const size = 10_000
+    for (let i = 0; i < size; i++) {
+      const temp = Math.random() * Number.MAX_SAFE_INTEGER
+      data.push(temp)
+      data2.push(temp)
+    }
+
+    // sort
+    introsort(data)
+    data2.sort()
+
+    // verify
+    let faulty = false
+    for (let i = 0; i < size; i++) {
+      if (data[i] !== data2[i]) {
+        faulty = true
+        break
+      }
+    }
+
+    expect(faulty).toEqual(false)
+  })
+})