Add test for calendar reducer

__tests__/reducers/__snapshots__/calendar.spec.js.snap

+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`calendar reducer initially should not be fetched 1`] = `
+Object {
+  "eventList": Array [],
+  "loading": true,
+  "status": "initial",
+}
+`;

__tests__/reducers/calendar.spec.js

+import reducer from '../../app/reducers/calendar';
+import * as actions from '../../app/actions/calendar';
+
+describe('calendar reducer', () => {
+  const initial = reducer();
+
+  describe('initially', () => {
+    it('should not be fetched', () => {
+      expect(initial).toMatchSnapshot();
+    });
+  });
+
+  describe('is refreshing', () => {
+    const state = reducer(
+      { loading: false },
+      actions.refresh(),
+    );
+
+    it('should be loading', () => {
+      expect(state).toHaveProperty('loading', true);
+    });
+  });
+
+  describe('is successful', () => {
+    const state = reducer(
+      initial,
+      actions.success([{ pk: 1 }]),
+    );
+
+    it('should not be loading', () => {
+      expect(state).toHaveProperty('loading', false);
+    });
+
+    it('should have events', () => {
+      expect(state).toHaveProperty('eventList', [{ pk: 1 }]);
+    });
+
+    it('should have status success', () => {
+      expect(state).toHaveProperty('status', 'success');
+    });
+  });
+
+  describe('is failure', () => {
+    const state = reducer(
+      initial,
+      actions.failure(),
+    );
+
+    it('should not be loading', () => {
+      expect(state).toHaveProperty('loading', false);
+    });
+
+    it('should not have events', () => {
+      expect(state).toHaveProperty('eventList', []);
+    });
+
+    it('should have status failure', () => {
+      expect(state).toHaveProperty('status', 'failure');
+    });
+  });
+
+});
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