jimbol

Feature flags

A simple feature flag implementation

Setup

A hash is provided for the current environment in the application setup.

type Features = { [FLAG_NAME]: Boolean | Function };
const features: Features = (NODE_ENV === 'production') ? productionFeatures : testingFeatures;
export featureFlag = setUpFeatureFlags(features, platform);

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const update = (id, hash, changes) => {
  const newHash = hash;
  const updateEntity = { ...newHash[id], ...changes };
  newHash[id] = updateEntity;
  return newHash;
};

const replace = (id, nextEntity, hash) => {
  let newHash = hash;
  newHash = remove(id, newHash);

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// ACTION FORMAT
// const scope = 'MY_SCOPE';
// const createAction = (id, payload) => ({
//   type: 'START_LOADING',
//   payload,
//   meta: {
//     scope,
//     type: EXPECT,
//     id,
//   },

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const lookUp = ({ hash, ids }) => ids.map((id) => hash[id]);

createTransformer({
  hash: getHash,
  ids: getIds,
}, lookUp, []);

const createTransformer = (dependencies, transformer, fallbackValue) => {
  return function(state, props, overrides) {
    const keys = Object.keys(dependencies);

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// my-reducer.js
function myReducer(plugins, state, action) {
  // ...
}

// reducers.js
import { myReducer } from './my-reducer';

export const reducers = {
  myReducers,

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0 == null; // false
'' == null; // false
undefined == null; // true

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// It gets hard to test combined selectors after a while.
// The dependency chains run deep.  To get around this we
// can test the callback function seperately from the rest
// of the selector, but that leaves a testing gap.

// In order to test that createSelector gets called with the
// right stuff, we could do something like this

// WARNING UNTESTED CODE

jimbol

Testing with Effect Runner

A Redux-Saga test runner for Mocha

Goals

• Switching the order of instructions should be easy
• Associate instructions with their results
• Changing instruction results should be easy

Guide

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// Having some sort of feature flags allows us to
// - write centralized logic around when to show features
// - develop features in smaller pieces behind feature flags
// - turn on/off features at will

// In a view, effect, whereever 
import features from '../features'

if (features('showFooBar')) {
  // display FooBar

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// In test file

const spy = effectSpy(generator)
  .next('init')
  .next('getToken', token) // name and pass in yield values
  .next('getUpdatedFooBars', fooBars)
  .next('putFooBars');

// in beforeEach
mySpyRun = spy.run({