Add Counter component tests

Author: alexandr-g

src/components/counter/Counter.spec.tsx

@@ -0,0 +1,73 @@
+import React from 'react'
+import { Provider } from 'react-redux'
+import { mount } from 'enzyme'
+import configureStore from 'redux-mock-store'
+
+import { actionTypes } from '../../features/counter'
+import Counter from './Counter'
+
+describe('Counter', () => {
+  const mockStore = configureStore([])
+  const store = mockStore({
+    count: {
+      value: 42,
+    },
+  })
+
+  // Add jest mock spy to watch for store.dispatch method. See https://jestjs.io/docs/en/jest-object#jestspyonobject-methodname for more info
+  jest.spyOn(store, 'dispatch')
+
+  beforeEach(() => {
+    // Clear any saved mock data from previous tests, because jest saves calls data for spies and mocks, https://jestjs.io/docs/en/mock-function-api#mockfnmockclear
+    store.dispatch.mockClear()
+  })
+
+  it('renders without crashing.', () => {
+    const wrapper = mount(
+      <Provider store={store}>
+        <Counter />
+      </Provider>
+    )
+
+    const countValue = wrapper.find('strong').text()
+    expect(countValue).toBe('42')
+  })
+
+  it('should be possible to increment counter.', () => {
+    const wrapper = mount(
+      <Provider store={store}>
+        <Counter />
+      </Provider>
+    )
+
+    wrapper
+      .find('button')
+      .filter({ 'data-qa': 'increment-counter' })
+      .simulate('click')
+
+    expect(store.dispatch).toBeCalledTimes(1)
+
+    expect(store.dispatch).toBeCalledWith({
+      type: actionTypes.INCREMENT_COUNTER,
+    })
+  })
+
+  it('should be possible to decrement counter.', () => {
+    const wrapper = mount(
+      <Provider store={store}>
+        <Counter />
+      </Provider>
+    )
+
+    wrapper
+      .find('button')
+      .filter({ 'data-qa': 'decrement-counter' })
+      .simulate('click')
+
+    expect(store.dispatch).toHaveBeenCalledTimes(1)
+
+    expect(store.dispatch).toHaveBeenCalledWith({
+      type: actionTypes.DECREMENT_COUNTER,
+    })
+  })
+})