Added edge cases to tests

test/squareSum.test.js

@@ -7,3 +7,11 @@ test('squareSum is a Function', () => {
 test('squareSum returns the proper result', () => {
   expect(squareSum(2, 3, 4)).toBe(29);
 });
+
+test('works with negative numbers', () => {
+  expect(squareSum(-2, 3, -4)).toBe(29);
+});
+
+test('NaN when parameters have text', () => {
+  expect(squareSum(-2, 3, -4, 'text')).toBe(NaN);
+});