Moved tests to __tests__, added prettier and updated jest

Author: Muhammad Bilal

.prettierrc

@@ -0,0 +1,8 @@
+{
+  "bracketSpacing": true,
+  "jsxSingleQuote": true,
+  "semi": true,
+  "singleQuote": true,
+  "tabWidth": 2,
+  "trailingComma": "none"
+}

package.json

@@ -25,7 +25,7 @@
     "eslint-config-prettier": "^6.4.0",
     "eslint-plugin-import": "^2.18.2",
     "eslint-plugin-prettier": "^3.1.1",
-    "jest": "^24.9.0",
+    "jest": "^27.0.6",
     "prettier": "1.18.2"
   }
 }

src/__tests__/arrays.test.js

@@ -0,0 +1,213 @@
+const {
+  getNthElement,
+  arrayToCSVString,
+  csvStringToArray,
+  addToArray,
+  addToArray2,
+  removeNthElement,
+  numbersToStrings,
+  uppercaseWordsInArray,
+  reverseWordsInArray,
+  onlyEven,
+  removeNthElement2,
+  elementsStartingWithAVowel,
+  removeSpaces,
+  sumNumbers,
+  sortByLastLetter
+} = require('../arrays');
+
+describe('getNthElement', () => {
+  const array = ['cat', 'dog', 'elephant', 'fox'];
+
+  xit('returns the element at the given position', () => {
+    expect(getNthElement(0, array)).toEqual('cat');
+    expect(getNthElement(2, array)).toEqual('elephant');
+    expect(getNthElement(3, array)).toEqual('fox');
+  });
+
+  xit('if n is greater than the number of elements, it cycles back to the start', () => {
+    expect(getNthElement(4, array)).toEqual('cat');
+    expect(getNthElement(5, array)).toEqual('dog');
+  });
+});
+
+describe('arrayToCSVString', () => {
+  xit('returns the array elements as a comma-seperated string', () => {
+    expect(arrayToCSVString(['a', 'b', 'c', 'd'])).toEqual('a,b,c,d');
+    expect(arrayToCSVString([1, 2, 3, 4, 5])).toEqual('1,2,3,4,5');
+  });
+});
+
+describe('csvStringToArray', () => {
+  xit('converts the csv string as an array', () => {
+    expect(csvStringToArray('a,b,c,d')).toEqual(['a', 'b', 'c', 'd']);
+    expect(csvStringToArray('1,2,3,4,5')).toEqual(['1', '2', '3', '4', '5']);
+  });
+});
+
+describe('addToArray', () => {
+  xit('adds the item to the end of the array', () => {
+    const array = [];
+    const array2 = [1, 2, 3];
+
+    expect(addToArray('a', array)).toEqual(undefined);
+    expect(addToArray(4, array2)).toEqual(undefined);
+
+    expect(array).toEqual(['a']);
+    expect(array2).toEqual([1, 2, 3, 4]);
+  });
+});
+
+describe('addToArray2', () => {
+  xit('returns a new array with the value appended', () => {
+    const array = ['a', 'b', 'c'];
+    const array2 = [1, 2, 3];
+
+    expect(addToArray2('d', array)).toEqual(['a', 'b', 'c', 'd']);
+    expect(array).toEqual(['a', 'b', 'c']);
+
+    expect(addToArray2(4, array2)).toEqual([1, 2, 3, 4]);
+    expect(array2).toEqual([1, 2, 3]);
+  });
+});
+
+describe('removeNthElement', () => {
+  xit('removes the element at position n', () => {
+    const array = ['ant', 'bison', 'cockerel', 'duck', 'elephant'];
+    removeNthElement(2, array);
+    expect(array).toEqual(['ant', 'bison', 'duck', 'elephant']);
+  });
+});
+
+describe('numbersToStrings', () => {
+  xit('converts every number in the array to a string', () => {
+    expect(numbersToStrings([1, 2, 3])).toEqual(['1', '2', '3']);
+  });
+});
+
+describe('uppercaseWordsInArray', () => {
+  xit('makes every string in the array uppercase', () => {
+    expect(uppercaseWordsInArray(['cat', 'mouse', 'banana'])).toEqual([
+      'CAT',
+      'MOUSE',
+      'BANANA'
+    ]);
+  });
+});
+
+describe('reverseWordsInArray', () => {
+  xit('reverses every string in an array', () => {
+    expect(reverseWordsInArray(['cat', 'Mouse', 'banana'])).toEqual([
+      'tac',
+      'esuoM',
+      'ananab'
+    ]);
+  });
+});
+
+describe('onlyEven', () => {
+  xit('filters the array and only returns even numbers', () => {
+    expect(onlyEven([1, 2, 3, 4, 5, 6, 7, 8])).toEqual([2, 4, 6, 8]);
+  });
+});
+
+describe('removeNthElement2', () => {
+  xit('returns an array with the nth element removed, and does not mutate the original', () => {
+    const array = ['bike', 'car', 'train', 'bus'];
+    expect(removeNthElement2(2, array)).toEqual(['bike', 'car', 'bus']);
+    expect(array).toEqual(['bike', 'car', 'train', 'bus']);
+  });
+});
+
+describe('elementsStartingWithAVowel', () => {
+  xit('returns elements starting with a vowel', () => {
+    expect(
+      elementsStartingWithAVowel([
+        'apple',
+        'bapple',
+        'capple',
+        'dapple',
+        'epple',
+        'fepple',
+        'gepple',
+        'hepple',
+        'ipple',
+        'jipple',
+        'kipple',
+        'lipple',
+        'mipple',
+        'nipple',
+        'opple',
+        'popple',
+        'qopple',
+        'ropple',
+        'sopple',
+        'topple',
+        'upple',
+        'vupple',
+        'wupple',
+        'xupple',
+        'yupple',
+        'zupple'
+      ])
+    ).toEqual(['apple', 'epple', 'ipple', 'opple', 'upple']);
+  });
+
+  xit('is case insensitive', () => {
+    expect(
+      elementsStartingWithAVowel([
+        'Apple',
+        'Bapple',
+        'Capple',
+        'Dapple',
+        'Epple',
+        'Fepple',
+        'Gepple',
+        'Hepple',
+        'Ipple',
+        'Jipple',
+        'Kipple',
+        'Lipple',
+        'Mipple',
+        'Nipple',
+        'Opple',
+        'Popple',
+        'Qopple',
+        'Ropple',
+        'Sopple',
+        'Topple',
+        'Upple',
+        'Vupple',
+        'Wupple',
+        'Xupple',
+        'Yupple',
+        'Zupple'
+      ])
+    ).toEqual(['Apple', 'Epple', 'Ipple', 'Opple', 'Upple']);
+  });
+});
+
+describe('removeSpaces', () => {
+  xit('returns the string with the space characters removed', () => {
+    expect(removeSpaces('this string has spaces')).toEqual(
+      'thisstringhasspaces'
+    );
+    expect(removeSpaces(' this one has sneaky   spaces ')).toEqual(
+      'thisonehassneakyspaces'
+    );
+  });
+});
+
+describe('sumNumbers', () => {
+  xit('returns the sum of the numbers in the array', () => {
+    expect(sumNumbers([1, 3, 5, 6, 2, 8])).toEqual(25);
+  });
+});
+
+describe('sortByLastLetter', () => {
+  xit('sorts the string by the last character', () => {
+    expect(
+      sortByLastLetter(['Lannister', 'Stark', 'Greyjoy', 'Targaryen'])
+    ).toEqual(['Stark', 'Targaryen', 'Lannister', 'Greyjoy']);
+  });
+});