test(create-app): add integration tests

[jamesgeorge007]

Description

This PR aims at adding an integration test suite for the create-app CLI utility.

Additional context

No

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other (Test update)

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[Shinigami92]

Nice 🙌

[antfu]

Thanks for your contributions! Can you describe a bit about the context why you want to add these tests? Having tests is good thing for sure, but I am a bit afraid of this could foot-gun contributors for future changes, which also require them to change the corresponding tests. As the logic here is fair simply and more UI oriented, I am a bit now sure if the value for testing this is worth-wise.

[Shinigami92]

I think it's a good thing also to have tests for the CLI, cause if someone ones to change it somehow, they get notified via tests if the CLI is still working as expected or if there is e.g. a breaking change.

[jamesgeorge007]

@antfu, thanks for raising your concerns. I do agree with @Shinigami92. For a CLI utility aimed at project scaffolding, there are a couple of things that are expected not to change. For instance, generating a project in the current directory and the associated validations. Also, there are project-specific implementations like the --template option. This PR aims at adding a test suite to ensure the minimum expectations. Adding a new template, or tweaking the CLI UI, doesn't require getting one's hands on the test suite.