Only starting applications (Ecto etc) if necessary when running tests

Phoenix Forum Questions / Help
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I’m finding that the startup time to run mix test on my Phoenix app is getting quite long (5–10 seconds). This isn’t a problem when running the whole suite, but is annoying when I’m test-driving a module that only contains pure functions, and doesn’t interact with the database etc.

For now, I’ve worked round it by using mix test --no-start where appropriate, and wrapping setup code in test_helper.exs with a check that the application is running, but it would be nice to run the tests with --no-start as the default, and start things as appropriate in setup hooks. I had a go at getting that set up, but couldn’t get the Ecto connection checkout stuff to work reliably (particularly with async enabled).

Has anyone got this kind of thing working, or am I embarking on a wild goose chase?

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One option could be to use a Mix alias to supply default arguments to the test task:

Finally, aliases can also be used to augment existing tasks. Let’s suppose you want to augment mix clean to clean another directory Mix does not know about:

[clean: ["clean", &clean_extra/1]]

So something like:

[test: ["test --no-start"]]
# or
[test: "test --no-start"]

What technique(s) have you been trying so far to start the Ecto Repo, and what sort of errors are you receiving?

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