Aexus Answers

Vitest: Enhanced Test Selection With Tags And Marks

Alex Johnson
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Vitest: Enhanced Test Selection With Tags And Marks

Hey guys! Let's dive into a super cool discussion about enhancing how we run tests in Vitest, focusing on using tags and marks. If you're coming from Pytest, you probably miss the flexibility of marking tests – it's a feature that can seriously streamline your workflow. There was a previous proposal (#5346) that didn't quite make the cut, but with Vitest v4 on the horizon, it's the perfect time to bring this up again.

The Problem: Fine-Grained Test Selection

In many test frameworks, selecting specific tests to run can be a bit clunky. You often end up running entire suites when you only need to focus on a subset of tests. This is where tags and marks come in handy. They allow you to categorize your tests and then run only the tests that match certain criteria. This is particularly useful in large projects where running all tests can take a significant amount of time.

Currently, Vitest offers some selection capabilities, notably the only() function. While helpful, it's not quite as flexible as a tagging system. Imagine you want to run all tests related to your API or database interactions – with tags, this becomes a breeze. Tags offer a more organized and scalable way to manage your tests, making it easier to target specific areas of your codebase.

Suggested Solution: Tagging Tests in Vitest

So, how can we bring the magic of tags to Vitest? Here are a couple of approaches inspired by Pytest and other frameworks:

Existing Functionality

Before we dive into the new stuff, let's quickly recap what Vitest already offers:

it.only('test', () => {})
test.skipIf(isDev)('prod only test', () => {})

it.only() is great for focusing on a single test during development, and test.skipIf() lets you conditionally skip tests based on your environment. These are useful tools, but tags take things to the next level.

Proposed Tagging Syntax

Here are a couple of ways we could implement tags in Vitest:

Option A

test.tags('domain1').it('should filter the data correctly', async () => { /* ... */});

This syntax is pretty clean. We chain the .tags() method onto the test object, passing in one or more tag names. This approach reads well and is easy to understand. Using chained methods makes the code expressive and maintainable.

Option B

test.tags('domain1')('should filter the data correctly', async () => { /* ... */});

This is a slightly more compact version of Option A. It's a matter of preference which one you find more readable. Both achieve the same goal: associating tags with a test.

Extended Example

To make things even more powerful, we can combine tags with existing Vitest features like skipIf():

test.tags('domain1').skipIf(isDev).it('should filter the data correctly', async () => { /* ... */});
// OR
test.tags('domain1').skipIf(isDev)('should filter the data correctly', async () => { /* ... */});

This allows you to create highly specific test configurations. For example, you might have tests tagged with 'domain1' that should be skipped in development environments. This level of control is invaluable in complex projects.

Original Proposal

For comparison, here's the syntax from the original proposal:

test('should filter the data correctly', { tags: ['domain1'] }, async () => { /* ... */});

While this works, the chained syntax (Options A and B) feels more aligned with Vitest's existing style and offers better readability.

Command-Line Interface (CLI) Enhancements

Of course, tagging tests is only half the battle. We also need a way to run tests based on their tags from the command line. Here's a suggested syntax for the Vitest CLI:

# Run tests for tasks having the tag "api" OR "auth"
vitest --run --tag api --tag auth

# Run tests for tasks having the tag "api" AND "auth"
vitest --run --tag api auth

# Pick test files that contain the word "user", exclude the tasks having the tag "api"
vitest user --run --no-tag api

# Prevent tasks with the tag "database" to be run in parallel
vitest --run --tag api --no-tag-parallelism database

Let's break this down:

  • vitest --run --tag api --tag auth: This would run tests tagged with either api OR auth. The use of multiple --tag flags implies an OR condition.
  • vitest --run --tag api auth: This would run tests tagged with BOTH api AND auth. Listing tags without the --tag flag implies an AND condition.
  • vitest user --run --no-tag api: This is super powerful! It runs tests in files containing "user" but excludes any tests tagged with api. This allows for complex filtering scenarios.
  • vitest --run --tag api --no-tag-parallelism database: This command runs tests tagged with api but prevents tests tagged with database from running in parallel. This is crucial for managing resources and avoiding conflicts in tests that interact with databases or other shared resources.

Benefits of Tagging

Implementing tags in Vitest would bring a ton of benefits:

  • Improved Test Organization: Tags provide a clear and consistent way to categorize tests.
  • Faster Test Runs: By running only the tests you need, you can save time and get feedback more quickly.
  • Better Collaboration: Tags make it easier for teams to understand the purpose of different tests.
  • More Flexible Testing Strategies: You can easily create different test suites for different purposes (e.g., smoke tests, integration tests, end-to-end tests).

Alternative Solutions

While tagging seems like the most intuitive solution, there might be other ways to achieve similar results. However, no specific alternatives were mentioned in the original discussion. Tags offer a balance of simplicity and power that makes them a compelling choice.

Additional Context and Resources

If you're curious about how other frameworks handle test marking, check out the Pytest documentation:

And here's Vitest's current guide on filtering tests:

Validations

This proposal adheres to the Vitest community guidelines:

Conclusion: Let's Make Vitest Even Better!

Guys, adding tags to Vitest would be a game-changer. It would make our testing workflows more efficient, more organized, and more enjoyable. Let's hope the Vitest team reconsiders this proposal for v4! It's a feature that many of us would love to see. This enhancement would significantly improve the developer experience and solidify Vitest's position as a top-tier testing framework.

For further reading on testing methodologies and best practices, you can check out resources on websites like https://testing.googleblog.com/. This blog offers valuable insights and information on software testing from Google's experts.

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