Create CLI

[anp]

This CLI should:

1. run snapshot tests in order
2. show interactive prompt at each failing test with test output diff and asking user whether to update
3. run any "marked for update" tests with UPDATE_SNAPSHOTS env var set
4. warn about any snap files on disk which don't correspond to tests ran during step 1

[RadicalZephyr]

FWIW I personally would not use the interactive CLI. I would want to be able to simply update all snapshots. The workflow I'm thinking I would use is something like:

• start from a clean version control revision
• update all snapshots with CLI tool
• use my version control diffing tools to see which tests have changed and how
• use my version control tools to discard changes to files that I don't want.
• commit

Another note about this is that it would be nicer in this paradigm for the files containing the test output to be only the result of the test. I'm kind of curious about that design decision btw. It seems to me that it would be simpler to encode the full rust module path to the test snapshot in the file path that holds the snapshot content. So for instance the file path to the test example in your blog post would change like:

-PATH_OF_TEST_FILE/__snapshots__/FILENAME_OF_TEST_FILE.snap
+PATH_OF_TEST_FILE/__snapshots__/FILENAME_OF_TEST_FILE/simple/test/simple_snapshot.snap`

Thoughts?

[anp]

use my version control tools to discard changes to files that I don't want.

My personal experience is that development tools are nicest to use when they minimize their assumptions about other tools in the environment. That said it's not like I have a lot of time for this at the moment!

It seems to me that it would be simpler to encode the full rust module path to the test snapshot in the file path that holds the snapshot content.

I believe this was an outcome of being in a rush and considering this experimental. PRs very welcome!