feat: add generated unit test to files automatically

[abeatrix]

Part of #1475

• Add new command for generating unit test in file so that it'd work with the edit command (will replace the old /test command once it's out of experimental)
• Set it behind a config cody.internal.unstable
• Add new EditMode file for inserting response to a different file (only used by /test currently)
• Generates new unsaved test files based on existing test files in codebase if LLM didn't provide us with a name suggestion
• Adds the generated test to the unsaved test file for users to review
• Some additional codebase cleanup for commands

Note

This will not affect the /test command used by agent. In a follow up PR I will add a param that allows all commands to be run in chat mode only

Test plan

0. Enable cody.internal.unstable
1. Run the /unit command in the selected code to generate unit tests
2. If there is a test file exists for the file that contains your selected code, the new unit tests will be added below the import statements in the file

• if the user is not happy with the generated tests, simply close the file with the unsaved change

3. If a test file does not exist for the selected file, the new unit tests will be added to a new unsaved file with the proposed file name for the new test file

• user can then review the file before hitting save

In addition, confirm the following works as expected:

• All existing tests are passing
• Other commands should not be affected by this change

Demo

demo_auto_test.mov

Follow-ups

To-dos in follow-up PRs:

• Add code lenses in the new test file with undo button
• Update prompt to eliminate duplicated imports in new tests

[umpox]

Feels really nice! Left some comments.

Mainly just wary of how we link Commands and Edits... It'd be awesome if we can abstract this slightly more - and might mean we can reuse this code easier in the future for any non-Command requirements

[abeatrix]

Feels really nice! Left some comments.

Mainly just wary of how we link Commands and Edits... It'd be awesome if we can abstract this slightly more - and might mean we can reuse this code easier in the future for any non-Command requirements

Thank you so much for your input @umpox! What you suggested makes sense and I've made some new changes in my local branch to reflect some of them.
I have some questions for you regarding the context fetching step, will discuss more during our 1:1 tomorrow. Thanks again for the review Tom!

[umpox]

This notification shows 🤔 It should usually only show if the file is not visible but I think it should be.

This is the code in streamTask:

            if (!visibleEditor) {
                await this.notifyTaskComplete(task)
            }

[umpox]

Looking really good, left some comments!

I noticed that it can duplicate some stuff when there's already an existing test file with tests in it. I wonder if there's a nice way to provide the precedingText if the test file already exists 🤔 We use precedingText for the add intent and it works well to avoid duplication. Maybe one for a follow up PR though

[abeatrix]

@umpox it's now behind an experimental configuration.

Regarding I noticed that it can duplicate some stuff when there's already an existing test file with tests in it. it's an existing issue that I will look into in a follow up PR since it's more of a prompting issue.