Added a failing implementation of NumberInputField mocking test.

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

-// import { render, screen } from '@testing-library/react';
+import { render, screen } from '@testing-library/react';
 import '../../testing/mockRedux.js';
-// import { NumberInputField, internals } from './numberInputField.js';
+import { NumberInputField} from './numberInputField.js';
 import numberInputFieldSlice from '../number-input-field/numberInputFieldSlice.js';
 
 import {
   selectNumberOfUnits,
   setNumberOfUnits,
 } from './numberInputFieldSlice.js';
-/*
+
 import {
   selectCurrentInputUnit,
-  selectCurrentOutputUnit,
 } from '../unit-selector/unitSelectorSlice.js';
-*/
 
 describe('the NumberInputField slice', () => {
   test('selects input value according to the store', () => {
@@ -43,26 +41,18 @@ describe('the NumberInputField slice', () => {
   });
 });
 
-jest.mock('./numberInputField.js', () => ({
-  selectNumberOfUnits: jest.fn().mockName('selectNumberOfUnits'),
-}));
-
+describe('the NumberInputField component', () => {
+  test('numberInputField displays apropriate content', () => {
     jest.mock('../unit-selector/unitSelectorSlice.js', () => ({
       selectCurrentInputUnit: jest.fn().mockName('selectCurrentInputUnit'),
-  selectCurrentOutputUnit: jest.fn().mockName('selectCurrentOutputUnit'),
     }));
 
-/*
-describe('the NumberInputField component', () => {
-  test('numberInputField displays apropriate content', () => {
-    selectNumberOfUnits.mockReturnValue(10);
     selectCurrentInputUnit.mockReturnValue('cm');
-    selectCurrentOutputUnit.mockReturnValue('cm');
 
-    render(<NumberInputField/>);
+    const { container } = render(<NumberInputField/>);
     expect(screen.getByLabelText('inputField')).toHaveAttribute(
       'placeholder', expect.stringContaining('Enter # of "cm"'),
     );
+    expect(container).toMatchSnapshot();
   });
 });
-*/

unit-conversion/src/features/unit-selector/unitSelector.test.js

-// import { render, screen } from '@testing-library/react';
 import '../../testing/mockRedux.js';
-// import { UnitSelector } from './unitSelector.js';
-
-/*
-import {
-  selectNumberOfUnits,
-} from '../number-input-field/numberInputFieldSlice.js';
-*/
 
 import unitSelectorSlice, {
   selectCurrentInputUnit,