wrote the test for sum.js and updated the sum function to check if the input is not NaN

Author: HadiVahidi20

Sprint-1/implement/sum.js

@@ -7,7 +7,7 @@ function sum(elements) {
         let current = elements[i]; // get the current element
 
         // Only add it if it's a number
-        if (typeof current === "number") {
+        if (typeof current === "number" && !Number.isNaN(current)) {
             total = total + current; // add to total
         }
     }

Sprint-1/implement/sum.test.js

@@ -13,24 +13,64 @@ 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("given an empty array, returns 0",()=>{
+    const currentOutput = sum([]);
+    const targetPitPut= 0;
+
+    expect(currentOutput).toEqual(targetPitPut);
+})
+
 
 // Given an array with just one number
 // When passed to the sum function
 // Then it should return that number
+test("given an array whit only 1 number, returns same input",()=>{
+    const currentOutput = sum([4]);
+    const targetPitPut= 4;
+
+    expect(currentOutput).toEqual(targetPitPut);
+})
+
 
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
+test("given an  array whit a negative number, returns correct total (subtract the negative number)",()=>{
+    const currentOutput = sum([1,2,3,4,-5,]);
+    const targetPitPut= 5;
+
+    expect(currentOutput).toEqual(targetPitPut);
+})
+
 
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
 
+test("given an  array whit a decimal/float number, returns correct total (decimal/float number)",()=>{
+    const currentOutput = sum([1,2,3,4,3.5,]);
+    const targetPitPut= 13.5;
+
+    expect(currentOutput).toEqual(targetPitPut);
+})
+
+
 // 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("given an  array whit a non-number values, returns correct total (ignore the NaN and sum the others)",()=>{
+    const currentOutput = sum([1,2,3,4,"hi",5]);
+    const targetPitPut= 15;
+
+    expect(currentOutput).toEqual(targetPitPut);
+})
 
 // 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("given an array with only non-number values, returns the least surprising value (0)", () => {
+    const currentOutput = sum(["hello", null, undefined, {}, [], true, NaN]);
+    const targetOutput = 0;
+
+    expect(currentOutput).toEqual(targetOutput);
+});