Vue Event Testing with TypeScript: Simulating User Interactions

This challenge focuses on writing robust unit tests for Vue components that handle user events. You'll be simulating user interactions (like clicks, input changes, and form submissions) and verifying that the component responds correctly. This is crucial for ensuring your Vue applications behave as expected and are resilient to different user actions.

Problem Description

You are tasked with creating a Vue component called CounterComponent that displays a counter and provides buttons to increment and decrement the counter. You need to write unit tests using a testing framework like Jest and Vue Test Utils to verify the component's behavior when these buttons are clicked. The tests should ensure that the counter value updates correctly and that any associated methods are called as expected.

What needs to be achieved:

1. Create a CounterComponent in Vue.js with TypeScript. This component should:
   • Display a counter value (initialized to 0).
   • Have two buttons: "Increment" and "Decrement".
   • Increment the counter value by 1 when the "Increment" button is clicked.
   • Decrement the counter value by 1 when the "Decrement" button is clicked.
2. Write unit tests for the CounterComponent using Jest and Vue Test Utils. These tests should:
   • Verify that the initial counter value is 0.
   • Verify that clicking the "Increment" button increases the counter value by 1.
   • Verify that clicking the "Decrement" button decreases the counter value by 1.
   • (Bonus) Verify that a custom method called resetCounter is called when a button with the id "reset" is clicked. This method should set the counter back to 0.

Key Requirements:

• Use TypeScript for both the component and the tests.
• Utilize Vue Test Utils for mounting the component and interacting with it.
• Employ Jest for running the tests.
• Ensure the tests are clear, concise, and well-documented.

Expected Behavior:

The tests should pass, indicating that the CounterComponent functions as intended and that the event handling logic is correct. The tests should accurately simulate user interactions and verify the resulting state changes.

Edge Cases to Consider:

• Decrementing the counter when it's already at 0 (should not go negative). While not explicitly required to test this, it's good practice to consider.
• Ensure the component updates correctly after multiple clicks.

Examples

Example 1:

Input: CounterComponent mounted, Increment button clicked once.
Output: Counter value changes from 0 to 1.
Explanation: The Increment button click triggers the increment method, updating the counter value.

Example 2:

Input: CounterComponent mounted, Decrement button clicked once.
Output: Counter value changes from 0 to -1.
Explanation: The Decrement button click triggers the decrement method, updating the counter value.

Example 3: (Bonus)

Input: CounterComponent mounted, Reset button clicked once.
Output: Counter value changes from any value to 0.
Explanation: The Reset button click triggers the resetCounter method, setting the counter value to 0.

Constraints

• The component should be a functional component using the <script setup> syntax.
• Tests should be written using Jest and Vue Test Utils.
• The component should be self-contained and not rely on external dependencies beyond Vue and Vue Test Utils.
• The tests should be reasonably performant (avoid unnecessary complexity).

Notes

• Consider using findComponent or find from Vue Test Utils to locate the buttons within the component.
• Use trigger from Vue Test Utils to simulate button clicks.
• Use getComponent or findComponent to access the counter value and assert its correctness.
• Think about how to best structure your tests to ensure they are readable and maintainable.
• The resetCounter method is optional, but provides a good opportunity to test additional event handling.