Mastering React Test-Driven Development

Handling the undo action

We'll create a new action, UNDO, which causes us to push the current state into a new array called past:

1. For this test, we can reuse the present and innerAction properties, so push those up into the outer describe block now. Also, define a new undoAction. We'll use it within our first test:

describe('withUndoRedo', () => {  const undoAction = { type: 'UNDO' };  const innerAction = { type: 'INNER' };  const present = { a: 123, nextInstructionId: 0 };  const future = { b: 234, nextInstructionId: 1 };  ...});

2. Add a new nested describe block with the following test and setup. The beforeEach block sets up a scenario where we've already performed an action that will have "saved" a previous state. We're then ready to undo ...