Q:

Snapshot test with Jest on nested react-navigation component - Object keys change so Snapshot match fails

When I run my jest test on my StackNavigator.test.js it always fails because of generated keys:
- Snapshot
+ Received

@@ -79,11 +79,11 @@
              fromRoute={null}
              index={0}
              navigation={
                Object {
                  "_childrenNavigation": Object {
-                   "**id-1542980055400-0**": Object {
+                   "**id-1542980068677-0**": Object {
                      "actions": Object {
                        "dismiss": [Function],
                        "goBack": [Function],
                        "navigate": [Function],
                        "pop": [Function],
@@ -109,11 +109,11 @@
                      "replace": [Function],
                      "reset": [Function],
                      "router": undefined,
                      "setParams": [Function],
                      "state": Object {
-                       "key": "**id-1542980055400-0**",
+                       "key": "**id-1542980068677-0**",
                        "routeName": "SignInOrRegister",
                      },
                    },
                  },
                  "actions": Object {
@@ -157,15 +157,15 @@
                  },
                  "setParams": [Function],
                  "state": Object {
                    "index": 0,
                    "isTransitioning": false,
-                   "key": "**id-1542980055400-1**",
+                   "key": "**id-1542980068677-1**",
                    "routeName": "FluidTransitionNavigator",
                    "routes": Array [
                      Object {
-                       "key": "**id-1542980055400-0**",
+                       "key": "**id-1542980068677-0**",
                        "routeName": "SignInOrRegister",
                      },
                    ],
                  },
                }
@@ -191,11 +191,11 @@
                    "overflow": "hidden",
                  },
                  undefined,
                ]
              }
-             toRoute="**id-1542980055400-0**"
+             toRoute="**id-1542980068677-0**"
            >
              <View
                style={
                  Object {
                    "bottom": 0,

The StackNavigator component uses 'react-navigation' and has a nested FluidTransition component from 'react-navigation-fluid-transitions':
StackNavigator.js
import React, { Component } from 'react';
import { Platform, Animated, Easing } from 'react-native';
import { createStackNavigator } from 'react-navigation';
import { ThemeContext, getTheme } from 'react-native-material-ui';
import PropTypes from 'prop-types'

import FluidTransitionNavigator from './FluidTransitionNavigator';
import Dashboard from './../pages/Dashboard';
import Login from './../pages/Login';
import SignInOrRegister from './../pages/SignInOrRegister';

import UniToolbar from './UniToolbar';

const transitionConfig = () => {
  return {
    transitionSpec: {
      duration: 1000,
      easing: Easing.out(Easing.poly(4)),
      timing: Animated.timing,
      useNativeDriver: false,
    },
    screenInterpolator: sceneProps => {
      const { layout, position, scene } = sceneProps

      const thisSceneIndex = scene.index
      const width = layout.initWidth

      const translateX = position.interpolate({
        inputRange: [thisSceneIndex - 1, thisSceneIndex],
        outputRange: [width, 0],
      })

      return { transform: [ { translateX } ] }
    },
  }
}

const StackNavigator = createStackNavigator(
  {
    FluidTransitionNavigator: {
      screen: FluidTransitionNavigator
    },
    Dashboard: {
      screen: Dashboard
    }
  },
  {
    initialRouteName: 'FluidTransitionNavigator',
    headerMode: 'float',
    navigationOptions: (props) => ({
      header: renderHeader(props)
    }),
    transitionConfig: transitionConfig
  }
);

const renderHeader = (props) => {
  let index = props.navigation.state.index;

  const logout = (props.navigation.state.routeName === 'Dashboard');
  let title = '';
  switch (props.navigation.state.routeName) {
    case 'Dashboard':
      title = 'Dashboard';
      break;
    case 'FluidTransitionNavigator':
      if (index ! == undefined) {
        switch (props.navigation.state.routes[index].routeName) {
          case 'Login':
            title = 'Sign In';
            break;
          case 'SignInOrRegister':
            title = 'SignInOrRegister';
            break;
          default:
            title = '';
        }
      }
      break;
    default:
      title = '';
  }

  return (['SignInOrRegister', 'Sign In'].includes(title)) ?  null : (
    <ThemeContext. Provider value={getTheme(uiTheme)} >
      <UniToolbar navigation={props.navigation} toolbarTitle={title} logout={logout} />
    </ThemeContext. Provider>
  );
};

renderHeader.propTypes = {
  navigation: PropTypes.object
};

const uiTheme = {
    toolbar: {
        container: {
          ...Platform.select({
            ios: {
              height: 70
            },
            android: {
              height: 76
            }
          })
        },
    },
};

export default StackNavigator;

Below is my test:
StackNavigator.test.js
import React from "react";
import renderer from "react-test-renderer";
import StackNavigator from "../StackNavigator";

test("renders correctly", () => {
  const tree = renderer.create(<StackNavigator />).toJSON();
  expect(tree).toMatchSnapshot();
});

I have seen a similar almost identical question here: Jest snapshot test failing due to react navigation generated key
The accepted answer still does not answer my question.  It did however lead me down another rabbit hole:
I tried to use inline matching: expect(tree).toMatchInlineSnapshot() to generate the tree after running yarn run test:unit and then tried to insert Any<String> in place of all the keys.  That did not work unfortunately. 
I'm stumped.  I don't know how to resolve this.  I have searched and searched, tried multiple things to get around it, I just can't solve this. 
Please can someone lend me a hand? 

A:

I solved my problem, but not by mocking Date.now which was suggested in many other cases. 
Instead I adapted an answer I found on https://github.com/react-navigation/react-navigation/issues/2269#issuecomment-369318490 by a user named joeybaker. 
The rationale for this was given as:

The keys aren't really important for your testing purposes.  What you
  really care about is the routes and the index. 

His code is as follows and assumes the use of actions and reducers in Redux:
// keys are date and order-of-test based, so just removed them
const filterKeys = (state) => {
  if (state.routes) {
    return {
      ...state,
      routes: state.routes.map((route) => {
        const { key, ...others } = route
        return filterKeys(others)
      }),
    }
  }
  return state
}

it('clears all other routes', () => {
    const inputState = {}
    const action = { type: AUTH_LOGOUT_SUCCESS }
    const state = filterKeys(reducer(inputState, action))
    expect(state.routes).toBe........
})

I have adapted this for my case (I do not use Redux yet) as follows:
test("renders correctly", () => {

  const tree = renderer.create(<StackNavigator />);
  const instance = tree.getInstance();
  const state = filterKeys(instance.state.nav);

  expect(state).toMatchSnapshot();
});

// keys are date and order-of-test based, so just removed them
const filterKeys = (state) => {
  if (state.routes) {
    return {
      ...state,
      routes: state.routes.map((route) => {
        const { key, ...others } = route
        return filterKeys(others);
      }),
    }
  }
  return state;
};

The test that gets rendered looks like this:
// Jest Snapshot v1

exports[`renders correctly 1`] = `
Object {
  "index": 0,
  "isTransitioning": false,
  "key": "StackRouterRoot",
  "routes": Array [
    Object {
      "index": 0,
      "isTransitioning": false,
      "routeName": "FluidTransitionNavigator",
      "routes": Array [
        Object {
          "routeName": "SignInOrRegister",
        },
      ],
    },
  ],
}
`;

