Vue Unit Testing #18 - Header progress component test

Summary

In this video script, the focus is on testing the functionality of a progress indicator using Tailwind CSS. The script outlines how to verify that the correct color class is applied based on the percentage value. It also explores testing user interactions, specifically checking that clicking on the progress indicator redirects users to the progress page. Additionally, the video demonstrates mocking functions, verifying event handling, and restoring mocks after testing. The overall approach combines CSS class validation with interaction testing to ensure robust front-end functionality.

Takeaways

• 😀 The progress indicator's color changes dynamically based on the current value of the percentage using Tailwind CSS classes.
• 😀 The proper class corresponding to the background color of the progress indicator is applied dynamically in the component.
• 😀 To test the dynamic class change, the HTML content of the rendered component needs to be checked for the appropriate class matching the current percentage value.
• 😀 Tests are written to check that the class applied to the progress indicator matches the expected color (e.g., blue or red).
• 😀 If the percentage or color class is changed in the component, the test is designed to fail if the color doesn't match the expected value.
• 😀 The next test scenario involves ensuring that clicking on the progress indicator redirects the user to the progress page.
• 😀 The behavior of clicking the progress indicator is emulated in tests by triggering a click event and verifying that the correct function is called.
• 😀 The navigate function, responsible for redirecting to the progress page, is imported from another module and spied on using Jest's spy function.
• 😀 In the test, the navigate function is checked to be called with the correct argument ('progress') after a click on the progress indicator.
• 😀 To ensure the accuracy of the tests, if the click listener is removed or the arguments change, the test is designed to fail, verifying that the function behavior is working as expected.
• 😀 After running the tests, all mocks are restored to their original state to ensure proper test isolation and prevent interference with other tests.

Q & A

What is the purpose of the progress indicator test in the script?

The purpose is to verify that the color of the progress indicator dot changes dynamically based on the percentage value. This ensures the UI accurately reflects progress in a visually intuitive way.

How does the test ensure that the correct Tailwind CSS class is applied?

The test checks the rendered HTML content of the progress indicator component. It verifies that the class responsible for the background color of the indicator matches the expected color class corresponding to the current percentage value.

What happens if the color class in the test is incorrectly set?

If the color class is incorrectly set, the test fails because it is expecting a specific class (e.g., 'blue') based on the percentage value, and any mismatch will trigger a failure.

How does the script handle the click event on the progress indicator?

The script simulates a click on the progress indicator using a test. It verifies that clicking triggers the `navigate` function from the router module, redirecting the user to the progress page.

How does the test ensure that the `navigate` function is called with the correct arguments?

The test uses a spy on the `navigate` function from the router module. It checks that the function is called once with the correct argument, which is the page name 'progress'.

What would cause the test for the click event to fail?

The test would fail if the click listener on the progress component is removed or if the `navigate` function is called with incorrect arguments, such as a different page name.

What role does mocking play in the tests?

Mocking is used to simulate the behavior of external dependencies, like the `navigate` function from the router module. This allows for testing the component behavior in isolation without relying on the actual router module.

What is the purpose of the `restoreMocks()` method?

The `restoreMocks()` method is called at the end of the test to reset all mocks to their original state. This ensures that mocks do not interfere with subsequent tests, maintaining a clean test environment.

How does the script test for dynamic changes in the color of the progress indicator?

The script tests dynamic changes by rendering the component with different values for the percentage and checking if the correct class (e.g., 'blue' or 'red') is applied. If the color doesn't match, the test fails.

What is the significance of printing out the HTML content of the component during testing?

Printing the HTML content of the component helps inspect the rendered structure and confirm whether the correct CSS class has been applied. It allows for debugging and ensuring the component behaves as expected in the test.