Vue Unit Testing #23 - Activity item component test

Summary

In this video, the instructor demonstrates how to refactor test code for improved readability and maintainability. By extracting the component mounting logic into a reusable function and using TypeScript’s `Partial` type to allow customizable activity objects, the process is streamlined. The video covers creating separate functions for mounting components and generating activity objects, and adjusting tests accordingly. The main goal is to reduce code repetition, improve test clarity, and ensure components are correctly rendered with dynamic data, using simple examples like checking if the activity name displays correctly in the component.

Takeaways

• 😀 Refactoring redundant code into reusable functions can improve code readability and maintainability.
• 😀 Moving the logic for mounting the component into a separate function reduces repetition across tests.
• 😀 The 'Mount activity item component' function is designed to mount the component and return the result for use in tests.
• 😀 Introducing a 'createActivity' function helps in generating activity objects with customizable fields, minimizing boilerplate code.
• 😀 The new 'createActivity' function uses default values for fields, which can be overridden using the 'Partial' TypeScript type.
• 😀 A new parameter, 'overwrites,' was added to the 'mountActivityItemComponent' function to allow passing custom properties into the component.
• 😀 The goal of refactoring is to make tests cleaner and easier to maintain by extracting repetitive logic into functions.
• 😀 The second test required passing activity objects as props to the component, which is handled by the new functions.
• 😀 A new test was introduced to verify that the activity name is properly rendered by the 'activity item' component.
• 😀 After the changes, all tests pass successfully, confirming that the refactoring worked as expected.

Q & A

Why is the refactoring necessary in the first place?

The refactoring is necessary because the logic to mount the component is repeated in multiple tests, which results in redundant code. By refactoring it into a reusable function, the code becomes cleaner and easier to maintain.

What is the purpose of the function `MountActivityItemComponent`?

The `MountActivityItemComponent` function is created to encapsulate the logic of mounting the component so it can be reused in multiple tests, avoiding repetition and making the test code more concise.

What additional functionality does the second test require that the first test does not?

The second test requires not just mounting the component but also passing an activity object as a prop. This necessitates creating a separate function for generating activity objects, which can be reused in the test.

Why does the activity object need to be passed into the `MountActivityItemComponent` function?

The activity object needs to be passed into the `MountActivityItemComponent` function because it is a prop that the component relies on to render. This allows the test to use a custom activity for each test scenario.

What is the role of the `createActivity` function?

The `createActivity` function is responsible for creating a new activity object. It allows customization of activity properties and is used to generate the activity object that gets passed to the component during testing.

What does the `partial` TypeScript type do in this context?

The `partial` TypeScript type makes the properties of the `activity` object optional, allowing for the overriding of specific fields without requiring all fields to be provided.

What is the advantage of renaming the parameter to `overwrites` in the `MountActivityItemComponent` function?

Renaming the parameter to `overwrites` clarifies that the object is used to overwrite specific properties of the default activity object, making the function's intent easier to understand.

How does passing the `activity` object to `MountActivityItemComponent` improve test readability?

Passing the `activity` object to `MountActivityItemComponent` makes the test more readable by clearly showing which activity object is being used in each test case. It also allows tests to customize the activity data more easily.

Why does the second test check that the component displays the activity name?

The second test checks that the component correctly renders the activity name to ensure that the component is properly receiving and displaying data passed via props, confirming the correctness of its rendering logic.

What happens if the `name` property is removed from the activity object in the test?

If the `name` property is removed, the test will fail because the component relies on the `name` property to display the activity name, and without it, the component's rendered output will not match the expected result.