Tests for actions, reducers, and thunks

chapter09/package-lock.json

@@ -9261,6 +9261,12 @@
       "integrity": "sha1-+wMJF/hqMTTlvJvsDWngAT3f7bI=",
       "dev": true
     },
+    "lodash.isplainobject": {
+      "version": "4.0.6",
+      "resolved": "https://registry.npmjs.org/lodash.isplainobject/-/lodash.isplainobject-4.0.6.tgz",
+      "integrity": "sha1-fFJqUtibRcRcxpC4gWO+BJf1UMs=",
+      "dev": true
+    },
     "lodash.memoize": {
       "version": "4.1.2",
       "resolved": "https://registry.npmjs.org/lodash.memoize/-/lodash.memoize-4.1.2.tgz",
@@ -12736,6 +12742,15 @@
         "deep-diff": "^0.3.5"
       }
     },
+    "redux-mock-store": {
+      "version": "1.5.3",
+      "resolved": "https://registry.npmjs.org/redux-mock-store/-/redux-mock-store-1.5.3.tgz",
+      "integrity": "sha512-ryhkkb/4D4CUGpAV2ln1GOY/uh51aczjcRz9k2L2bPx/Xja3c5pSGJJPyR25GNVRXtKIExScdAgFdiXp68GmJA==",
+      "dev": true,
+      "requires": {
+        "lodash.isplainobject": "^4.0.6"
+      }
+    },
     "redux-thunk": {
       "version": "2.3.0",
       "resolved": "https://registry.npmjs.org/redux-thunk/-/redux-thunk-2.3.0.tgz",

chapter09/package.json

@@ -23,7 +23,8 @@
         "react-devtools": "^3.2.3",
         "react-scripts": "1.1.4",
         "react-test-renderer": "^16.4.2",
-        "redux-devtools-extension": "^2.13.5"
+        "redux-devtools-extension": "^2.13.5",
+        "redux-mock-store": "^1.5.3"
     },
     "dependencies": {
         "axios": "^0.18.0",

chapter09/src/regionsApp/world.actions.js

@@ -72,6 +72,20 @@ export const getCountries = () => async dispatch => {
     }
 };
 
+export const getCountries2 = () => async (dispatch, getState) => {
+    if (getState().countries.length) {
+        // no need to do anything!
+    } else {
+        try {
+            dispatch(countriesRequest());
+            const result = await getCountriesAPI();
+            dispatch(countriesSuccess(result.data));
+        } catch (e) {
+            dispatch(countriesFailure());
+        }
+    }
+};
+
 export const getRegions = (country: string) => async dispatch => {
     if (country) {
         try {

chapter09/src/regionsApp/world.actions.test.js

@@ -0,0 +1,77 @@
+/* @flow */
+
+import configureMockStore from "redux-mock-store";
+import thunk from "redux-thunk";
+
+import {
+    getCountries,
+    getCountries2,
+    countriesSuccess,
+    COUNTRIES_REQUEST,
+    COUNTRIES_SUCCESS,
+    COUNTRIES_FAILURE
+} from "./world.actions.js";
+
+import { getCountriesAPI } from "./serviceApi";
+
+let mockPromise;
+jest.mock("./serviceApi", () => {
+    return {
+        getCountriesAPI: jest.fn().mockImplementation(() => mockPromise)
+    };
+});
+
+describe("getCountries", () => {
+    it("on API success", async () => {
+        const fakeCountries = {
+            data: [{ code: "UY" }, { code: "AR" }, { code: "BR" }]
+        };
+        mockPromise = Promise.resolve(fakeCountries);
+
+        const store = configureMockStore([thunk])({});
+
+        await store.dispatch(getCountries());
+
+        const dispatchedActions = store.getActions();
+
+        expect(getCountriesAPI).toHaveBeenCalledWith();
+        expect(dispatchedActions.length).toBe(2);
+        expect(dispatchedActions[0].type).toBe(COUNTRIES_REQUEST);
+        expect(dispatchedActions[1].type).toBe(COUNTRIES_SUCCESS);
+        expect(dispatchedActions[1].listOfCountries).toEqual(
+            fakeCountries.data
+        );
+
+        /*
+            We could have written... but then we'd need tests for countriesSuccess()
+        */
+        expect(dispatchedActions[1]).toEqual(
+            countriesSuccess(fakeCountries.data)
+        );
+    });
+
+    it("on API failure", async () => {
+        mockPromise = Promise.reject(new Error("failure!"));
+
+        const store = configureMockStore([thunk])({});
+
+        await store.dispatch(getCountries());
+
+        const dispatchedActions = store.getActions();
+
+        expect(getCountriesAPI).toHaveBeenCalledWith();
+        expect(dispatchedActions.length).toBe(2);
+        expect(dispatchedActions[0].type).toBe(COUNTRIES_REQUEST);
+        expect(dispatchedActions[1].type).toBe(COUNTRIES_FAILURE);
+    });
+});
+
+describe("getCountries2", () => {
+    it("doesn't do unneeded calls", async () => {
+        const store = configureMockStore([thunk])({
+            countries: [{ land: 1 }, { land: 2 }]
+        });
+        await store.dispatch(getCountries2());
+        expect(store.getActions().length).toBe(0);
+    });
+});

chapter09/src/regionsApp/world.reducer.test.js

@@ -1,13 +1,8 @@
 /* @flow */
 
-import Enzyme from "enzyme/build";
-import Adapter from "enzyme-adapter-react-16/build";
-
 import { reducer } from "./world.reducer.js";
 import { countriesRequest, regionsSuccess } from "./world.actions.js";
 
-Enzyme.configure({ adapter: new Adapter() });
-
 describe("The countries and regions reducer", () => {
     it("should process countryRequest actions", () => {
         const initialState = {