Added unit tests for all project reducers.

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

 // import { render, screen } from '@testing-library/react';
 import '../../testing/mockRedux.js';
 // import { NumberInputField, internals } from './numberInputField.js';
+import numberInputFieldSlice from '../number-input-field/numberInputFieldSlice.js';
 
 import {
   selectNumberOfUnits,
+  setNumberOfUnits,
 } from './numberInputFieldSlice.js';
 /*
 import {
@@ -29,6 +31,18 @@ describe('the NumberInputField slice', () => {
   });
 });
 
+describe('the NumberInputField slice', () => {
+  test('setNumberOfUnits correctly adjusts state value', () => {
+    // This is what the local state looks like to the "setNumberOfUnits" reducer.
+    const state = numberInputFieldSlice.reducer({
+      numberToConvert: 10,
+    }, setNumberOfUnits(100));
+
+    const numberOfUnits = 100;
+    expect(state.numberToConvert).toEqual(numberOfUnits);
+  });
+});
+
 jest.mock('./numberInputField.js', () => ({
   selectNumberOfUnits: jest.fn().mockName('selectNumberOfUnits'),
 }));

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

@@ -8,9 +8,11 @@ import {
 } from '../number-input-field/numberInputFieldSlice.js';
 */
 
-import {
+import unitSelectorSlice, {
   selectCurrentInputUnit,
   selectCurrentOutputUnit,
+  setCurrentInputUnit,
+  setCurrentOutputUnit,
 } from './unitSelectorSlice.js';
 
 describe('the UnitSelector slice', () => {
@@ -46,3 +48,27 @@ describe('the UnitSelector slice', () => {
     expect(selectedOutputUnit).toEqual('cm');
   });
 });
+
+describe('the UnitSelector slice', () => {
+  test('setcurrentInputUnit correctly adjusts state value', () => {
+    // This is what the local state looks like to the "setCurrentInputUnit" reducer.
+    const state = unitSelectorSlice.reducer({
+      currentInputUnit: 'm',
+      currentOutputUnit: 'cm',
+    }, setCurrentInputUnit('km'));
+
+    expect(state.currentInputUnit).toEqual('km');
+  });
+});
+
+describe('the UnitSelector slice', () => {
+  test('setcurrentOutputUnit correctly adjusts state value', () => {
+    // This is what the local state looks like to the "setCurrentOutputUnit" reducer.
+    const state = unitSelectorSlice.reducer({
+      currentInputUnit: 'm',
+      currentOutputUnit: 'cm',
+    }, setCurrentOutputUnit('km'));
+
+    expect(state.currentOutputUnit).toEqual('km');
+  });
+});