feat(store): adding an internal setting _ngrxMockEnvironment

Closes ngrx#2363

modules/store/src/flags.ts

@@ -0,0 +1,7 @@
+let _ngrxMockEnvironment = false;
+export function setNgrxMockEnvironment(value: boolean): void {
+  _ngrxMockEnvironment = value;
+}
+export function isNgrxMockEnvironment(): boolean {
+  return _ngrxMockEnvironment;
+}

modules/store/src/index.ts

@@ -14,6 +14,7 @@ export {
 export { createAction, props, union } from './action_creator';
 export { Store, select } from './store';
 export { combineReducers, compose, createReducerFactory } from './utils';
+export { setNgrxMockEnvironment, isNgrxMockEnvironment } from './flags';
 export { ActionsSubject, INIT } from './actions_subject';
 export {
   ReducerManager,

modules/store/src/selector.ts

@@ -1,4 +1,5 @@
 import { Selector, SelectorWithProps } from './models';
+import { isNgrxMockEnvironment } from './flags';
 import { isDevMode } from '@angular/core';
 
 export type AnyFn = (...args: any[]) => any;
@@ -613,7 +614,7 @@ export function createFeatureSelector(
 ): MemoizedSelector<any, any> {
   return createSelector((state: any) => {
     const featureState = state[featureName];
-    if (isDevMode() && !(featureName in state)) {
+    if (!isNgrxMockEnvironment() && isDevMode() && !(featureName in state)) {
       console.warn(
         `@ngrx/store: The feature name \"${featureName}\" does ` +
           'not exist in the state, therefore createFeatureSelector ' +

modules/store/testing/src/testing.ts

@@ -6,6 +6,7 @@ import {
   ReducerManager,
   StateObservable,
   Store,
+  setNgrxMockEnvironment,
 } from '@ngrx/store';
 import { MockStore } from './mock_store';
 import { MockReducerManager } from './mock_reducer_manager';
@@ -20,6 +21,7 @@ export interface MockStoreConfig<T> {
 export function provideMockStore<T = any>(
   config: MockStoreConfig<T> = {}
 ): Provider[] {
+  setNgrxMockEnvironment(true);
   return [
     ActionsSubject,
     MockState,