Vue Unit Testing #3 - Button component test

Summary

This tutorial demonstrates how to write tests for a Vue.js `BaseButton` component, ensuring that different button types are rendered with the appropriate classes. It starts by testing the `danger` button type and uses TypeScript for stricter prop typing. The script then introduces parameterized tests, allowing the testing of multiple button types in a single function. The tests are verified by deliberately breaking the implementation to ensure error handling works as expected. The video emphasizes the importance of reusable, generalized tests to ensure all button types are correctly rendered with the right classes.

Takeaways

• 😀 Test the BaseButton component to ensure the correct classes are assigned based on the button type (e.g., 'danger').
• 😀 Begin by writing a basic test that checks if the 'danger' button type renders with the appropriate set of classes.
• 😀 Use TypeScript to enforce proper typing by ensuring the 'type' prop is referenced correctly with a custom type ('buttonType').
• 😀 Update the test to cover all button types, not just 'danger', by using a more generalized testing approach.
• 😀 Leverage parameterized or data-driven tests using `.each` to handle multiple button types dynamically in one test.
• 😀 Store each button type and its corresponding classes in an array of objects to be used in the parameterized test.
• 😀 The test description is made dynamic by referencing the button 'type' property to handle all button types generically.
• 😀 For each button type, destructure the data object to dynamically reference the 'type' and 'classes' for each test case.
• 😀 Ensure that any change in the button component (like swapping button classes) causes the test to fail, proving the test’s accuracy.
• 😀 Finally, run all the tests in the project and confirm that all tests are executed successfully without any issues.

Q & A

What is the main purpose of the test in the lesson?

The main purpose of the test is to ensure that the `BaseButton` component renders the appropriate classes for different button types when the `type` prop is passed.

How does the instructor ensure the `BaseButton` component handles the 'danger' button type correctly?

The instructor writes a test to check if the `danger` button type is rendered with the correct set of classes. The test ensures the proper button type is displayed by verifying the button's class names.

What changes are made after testing for the 'danger' button type?

After testing for the `danger` button type, the test is refactored to check all button types. This is achieved by using a data-driven test approach, allowing the test to handle multiple button types in one go.

What is a parameterized test, and how is it used in this lesson?

A parameterized test (also known as a data-driven test) is a test that runs multiple times with different sets of data. In this lesson, the instructor uses the `.each` method to run the test for each button type, passing different button types and their corresponding CSS classes.

How does the `.each` method work in the context of the test?

The `.each` method iterates over an array of objects, where each object contains a button type and its corresponding class names. For each object, the test is executed with the respective type and classes, ensuring that all button types are tested.

What is the significance of the 'type' and 'classes' keys in the test data?

The 'type' key represents the button type being tested (e.g., 'danger'), and the 'classes' key stores the corresponding CSS classes that should be applied when the button type is rendered.

Why does the instructor verify that the test throws an error when button type classes are changed?

The instructor verifies that the test throws an error when the classes are changed to ensure that the button rendering is dependent on the correct classes. This helps in catching errors when button styles are altered incorrectly.

How is TypeScript used in this lesson to ensure proper type checking for the 'type' prop?

TypeScript is used to ensure that the 'type' prop is not just a string, but a specific custom type called 'button type'. This helps avoid passing incorrect values to the `BaseButton` component and ensures type safety.

What is the role of the 'buttonType' in the TypeScript code?

The 'buttonType' is a custom type defined in a TypeScript file ('types.ts') that contains all the valid button types. This ensures that only valid button types are passed to the `BaseButton` component, preventing runtime errors.

How does the instructor finalize the testing process in this lesson?

The instructor runs all the tests in the project to ensure everything is functioning correctly. After ensuring that all tests pass successfully, the lesson concludes.