Add tests for SetPasscode screen

src/screens/SetPasscode.js

@@ -5,7 +5,7 @@ import PasscodeForm from '../components/PasscodeForm';
 import { setPasscode, getCurrentPasscode } from '../redux/modules/settings';
 import { hashString } from '../utils/crypto';
 
-class SetPasscode extends React.Component {
+export class SetPasscode extends React.Component {
   static navigationOptions = {
     title: 'Set Passcode',
   };
@@ -15,7 +15,7 @@ class SetPasscode extends React.Component {
   }
 }
 
-const mapDispatchToProps = (dispatch, ownProps) => ({
+export const mapDispatchToProps = (dispatch, ownProps) => ({
   handlePasscodeSubmit(passcode) {
     dispatch(setPasscode(hashString(passcode)));
     ownProps.navigation.goBack();

src/screens/SetPasscode.test.js

@@ -0,0 +1,38 @@
+import React from 'react';
+
+import {
+  SetPasscode,
+  mapDispatchToProps as dispatchProps,
+} from './SetPasscode';
+
+import { SET_PASSCODE } from '../redux/modules/settings';
+
+describe('SetPasscode screen test', () => {
+  it('should render as expected', () => {
+    const wrapper = shallow(<SetPasscode />);
+    expect(wrapper).toMatchSnapshot();
+  });
+
+  describe('mapDispatchToProps test', () => {
+    it('should set the hashed passcode on submit and go back one route', () => {
+      const dispatchMock = jest.fn();
+      const ownPropsMock = {
+        navigation: {
+          goBack: jest.fn(),
+        },
+      };
+      const props = dispatchProps(dispatchMock, ownPropsMock);
+      props.handlePasscodeSubmit('password');
+      expect(dispatchMock.mock.calls.length).toBe(1);
+      expect(dispatchMock.mock.calls[0]).toEqual([
+        {
+          passcodeHash:
+            '5e884898da28047151d0e56f8dc6292773603d0d6aabbdd62a11ef721d1542d8',
+          type: SET_PASSCODE,
+        },
+      ]);
+
+      expect(ownPropsMock.navigation.goBack.mock.calls.length).toBe(1);
+    });
+  });
+});

src/screens/__snapshots__/SetPasscode.test.js.snap

@@ -0,0 +1,3 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`SetPasscode screen test should render as expected 1`] = `<PasscodeForm />`;