fixed sum function and wrote tests

Author: alizada-dev

Sprint-1/implement/sum.js

@@ -1,4 +1,9 @@
 function sum(elements) {
+
+    // const filteredArr = elements.filter(x => typeof x === 'number');
+    // return filteredArr.reduce((a, b) => a + b, 0);
+
+    return elements.filter(x => typeof x === 'number').reduce((a, b) => a + b, 0);
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -13,24 +13,49 @@ const sum = require("./sum.js");
 // Given an empty array
 // When passed to the sum function
 // Then it should return 0
-test.todo("given an empty array, returns 0")
+
+test("return 0 for an empty array", () => {
+    expect(sum([])).toEqual(0);
+})
 
 // Given an array with just one number
 // When passed to the sum function
 // Then it should return that number
 
+test("given an array with just one number, return that number", () => {
+    expect(sum([3])).toEqual(3);
+    expect(sum([-3])).toEqual(-3);
+    expect(sum([0])).toEqual(0);
+})
+
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
 
+test("return the correct total when passed negative numbers", () => {
+    expect(sum([-3, -6, -1])).toEqual(-10);
+})
+
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
+test("decimal number arrays", () => {
+    expect(sum([0.2, 0.4, 0.2])).toEqual(0.8);
+})
 
 // Given an array containing non-number values
 // When passed to the sum function
 // Then it should ignore the non-numerical values and return the sum of the numerical elements
 
+test("an array with non-numbers", () => {
+    expect(sum([2, "Blue", 3, "Black", "Green"])).toEqual(5);
+})
+
 // Given an array with only non-number values
 // When passed to the sum function
 // Then it should return the least surprising value given how it behaves for all other inputs
+
+test("an array with non-number values only", () => {
+    expect(sum([true, false, "Black"])).toEqual(0);
+    expect(sum([undefined, null, "Black"])).toEqual(0);
+})