Given a record of your Dict functions, this function will run a comprehensive suite of tests against them, comparing them to the elm/core Dict.

It will:

• Create the initial Dict using a random constructor (like empty, singleton or fromList)
• Run a random sequence of "updating" actions on it (like insert, filter, diff etc.)
• Query the final Dict using a random function (like size, get, partition, toList etc.)

The process above will run on both your Dict and the elm/core Dict in tandem. (The same commands will run for both.)

There should be no visible difference in behaviour: eg. order of items given from toList should be the same.

This helps prevent subtle surprises when users switch between Dict implementations, like update key (\_ -> Nothing) not removing items from the Dict (a real bug in one of the 3rd-party Dicts!).

Provide your functions. Typically something like the below example.

Note: you can opt out of testing some functions with Nothing, but beware: not providing eg. toList will result in almost no tests being actually ran.

-- Debug.toString
{ dictToString = Debug.toString


-- Creation
, empty = Just <| OpaqueDict.empty identity
, singleton = Just <| OpaqueDict.singleton identity
, fromList = Just <| OpaqueDict.fromList identity


-- Updating
, insert = Just OpaqueDict.insert
, update = Just OpaqueDict.update
, remove = Just OpaqueDict.remove
, map = Just OpaqueDict.map
, filter = Just OpaqueDict.filter
, union = Just OpaqueDict.union
, intersect = Just OpaqueDict.intersect
, diff = Just OpaqueDict.diff


-- Querying
, size = Just OpaqueDict.size
, isEmpty = Just OpaqueDict.isEmpty
, member = Just OpaqueDict.member
, get = Just OpaqueDict.get
, toList = Just OpaqueDict.toList
, foldl = Just OpaqueDict.foldl
, foldr = Just OpaqueDict.foldr
, partition = Just OpaqueDict.partition
, keys = Just OpaqueDict.keys
, values = Just OpaqueDict.values
, merge = Just OpaqueDict.merge
}