sum function created & test cases created

Author: mervereis

Sprint-1/implement/sum.js

@@ -1,4 +1,12 @@
 function sum(elements) {
+  const numbers = elements.filter((el) => typeof el === "number");
+
+  if (numbers.length === 0) return 0;
+
+  if (numbers.length === 1) return numbers[0];
+
+  const sumNumbers = numbers.reduce((a, b) => a + b, 0);
+  return sumNumbers;
 }
 
 module.exports = sum;

Sprint-1/implement/sum.test.js

@@ -1,36 +1,45 @@
-/* Sum the numbers in an array
-
-In this kata, you will need to implement a function that sums the numerical elements of an array
-
-E.g. sum([10, 20, 30]), target output: 60
-E.g. sum(['hey', 10, 'hi', 60, 10]), target output: 80 (ignore any non-numerical elements)
-*/
-
 const sum = require("./sum.js");
 
-// Acceptance Criteria:
-
-// Given an empty array
-// When passed to the sum function
-// Then it should return 0
-test.todo("given an empty array, returns 0")
-
-// Given an array with just one number
-// When passed to the sum function
-// Then it should return that number
-
-// Given an array containing negative numbers
-// When passed to the sum function
-// Then it should still return the correct total sum
-
-// Given an array with decimal/float numbers
-// When passed to the sum function
-// Then it should return the correct total sum
-
-// 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
-
-// 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
+describe("sum", () => {
+  // Given an empty array
+  // When passed to the sum function
+  // Then it should return 0
+  test("given an empty array, returns 0", () => {
+    expect(sum([])).toBe(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 one number, returns that number", () => {
+    expect(sum([5])).toBe(5);
+  });
+
+  // Given an array containing negative numbers
+  // When passed to the sum function
+  // Then it should still return the correct total sum
+  test("sums negative numbers correctly", () => {
+    expect(sum([-5, -10, 15])).toBe(0);
+  });
+
+  // Given an array with decimal/float numbers
+  // When passed to the sum function
+  // Then it should return the correct total sum
+  test("sums decimal numbers correctly", () => {
+    expect(sum([1.5, 2.5, 3.5])).toBe(7.5);
+  });
+
+  // Given an array containing non-number values
+  // When passed to the sum function
+  // Then it should ignore the non-numerical values
+  test("ignores non-number values", () => {
+    expect(sum(["hey", 10, "hi", 60, 10])).toBe(80);
+  });
+
+  // Given an array with only non-number values
+  // When passed to the sum function
+  // Then it should return the least surprising value
+  test("returns 0 when array contains only non-number values", () => {
+    expect(sum(["a", "b", "c"])).toBe(0);
+  });
+});