Added return value mocking to the component unit test.

unit-conversion/src/features/number-input-field/__snapshots__/numberInputField.test.js.snap

@@ -13,7 +13,7 @@ exports[`the NumberInputField component numberInputField displays apropriate con
     <input
       class="inputField"
       id="inputField"
-      placeholder="Enter # of \\"undefined\\""
+      placeholder="Enter # of \\"cm\\""
       type="text"
     />
   </div>

unit-conversion/src/features/number-input-field/numberInputField.test.js

@@ -8,11 +8,9 @@ import {
   setNumberOfUnits,
 } from './numberInputFieldSlice.js';
 
-/*
 import {
   selectCurrentInputUnit,
 } from '../unit-selector/unitSelectorSlice.js';
-*/
 
 jest.mock('../unit-selector/unitSelectorSlice.js', () => ({
   selectCurrentInputUnit: jest.fn().mockName('selectCurrentInputUnit'),
@@ -49,12 +47,11 @@ describe('the NumberInputField slice', () => {
 
 describe('the NumberInputField component', () => {
   test('numberInputField displays apropriate content', () => {
-    // HOW DO I GET THIS TO WORK????
-    // selectCurrentInputUnit.mockReturnValue('cm');
+    selectCurrentInputUnit.mockReturnValue('cm');
 
     const { container } = render(<NumberInputField/>);
     expect(screen.getByLabelText('inputField')).toHaveAttribute(
-      'placeholder', expect.stringContaining('Enter # of "undefined"'),
+      'placeholder', expect.stringContaining('Enter # of "cm"'),
     );
     expect(container).toMatchSnapshot();
   });

unit-conversion/src/setupTests.js

 import '@testing-library/jest-dom/extend-expect';
+
+afterEach(() => {
+  jest.clearAllMocks();
+});