Making `Browser.application.init` testable?

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I am curious if there is some simple way to modify the definition of init to make it possible to test it directly?

init : flags -> Url -> Key -> ( model, Cmd msg )

I am not sure if I even want to be implementing tests at such a high level, but I was just curious.

I’m guessing people will recommend that I define a helper function like:

initHelper : flags -> Url -> (Model a -> Model a) -> ( Model a, Cmd msg)

to abstract references to the Key, if my model stores the Key.

I am also curious to read through full test suites for larger Elm apps.

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https://elm-program-test.netlify.app/ does exactly that.

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That library looks nice.

Looks like you need to slightly reorganize your program to use it: elm-program-test/NavigationKeyExample.elm at main · avh4/elm-program-test · GitHub

I might try something simpler that is focused on init only to get going.

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As I reflect more on this, if elm/browser chooses to hide the implementation of Key, then elm/browser should also provide some utilities for testing contexts. It feels like a lot of noise to have to define an effect variant for each potential command occurring after init/update.

I also noticed that the elm/browser package does not have a test suite. For a community that uses testability as a selling point, I would generally expect all core libraries have test suites easily browseble on GitHub close to the source code.

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