adding some redux steps

step2-06/src/reducers/pureFunctions.spec.ts

@@ -0,0 +1,20 @@
+import { addTodo } from './pureFunctions';
+import { Store } from '../store';
+
+describe('TodoApp reducers', () => {
+  it('can add an item', () => {
+    const state = <Store>{
+      todos: {},
+      filter: 'all'
+    };
+
+    const newState = addTodo(state, 'item1');
+
+    const keys = Object.keys(newState.todos);
+
+    expect(newState).not.toBe(state);
+    expect(keys.length).toBe(1);
+    expect(newState.todos[keys[0]].label).toBe('item1');
+    expect(newState.todos[keys[0]].completed).toBeFalsy();
+  });
+});