Merge #3204

3204: Remove wallet types from coin selection test suite. r=jonathanknowles a=jonathanknowles

## Issue Numbers

Epic: ADP-1448 (_Coin Selection Type Generalization: Part 1_)

Tasks: ADP-1527, ADP-1528, ADP-1529, ADP-1530, ADP-1531.

## Summary

This PR adjusts the following modules:
- `CoinSelection.InternalSpec`
- `CoinSelection.Internal.BalanceSpec`
- `CoinSelection.Internal.CollateralSpec`
- `Primitive.Types.UTxOIndexSpec`
- `Primitive.Types.UTxOSelectionSpec`

Within these modules, we remove all usages of the following types:
- `Primitive.Types.Address`
- `Primitive.Types.TxIn`
- `Primitive.Types.TxOut`

To achieve this, we replace our dependency on `WalletSelectionContext` with a new `TestSelectionContext`:

```patch
- instance SelectionContext WalletSelectionContext where
-     type Address WalletSelectionContext = W.Address
-     type UTxO    WalletSelectionContext = W.WalletUTxO
+ instance SelectionContext TestSelectionContext where
+     type Address TestSelectionContext = TestAddress
+     type UTxO    TestSelectionContext = TestUTxO
```

From the point of view of the coin selection algorithm, the actual concrete types used for `Address ctx` and `UTxO ctx` are **_not important_**: it's **_only_** important that these types have `Ord`, `Show`, and `Buildable` instances. For the test suite, it's also important that these types have `Arbitrary` and `CoArbitrary` instances.

With that in mind, we define types `TestAddress` and `TestUTxO` in terms of the `Quid` (quasi-unique identifier) type, which provides support for **_deriving_** all these instances **_automatically_**:

```hs
newtype TestAddress = TestAddress (Hexadecimal Quid)
    deriving (Arbitrary, CoArbitrary) via Quid
    deriving Buildable via Pretty TestAddress
    deriving stock (Eq, Ord, Read, Show)

newtype TestUTxO = TestUTxO (Hexadecimal Quid)
    deriving (Arbitrary, CoArbitrary) via Quid
    deriving Buildable via Pretty TestUTxO
    deriving stock (Eq, Ord, Read, Show)
```

The `Arbitrary` instance for `Quid` generates values of a **_length_** that is governed by the QuickCheck size parameter. By adjusting the size parameter, we can control the level of "uniqueness" of generated `Quid` values, and the frequency of collisions:

- Choosing a **_lower value_** for the size parameter results in **_less uniqueness_,** and a **_higher rate_** of collisions.
- Choosing a **_higher value_** for the size parameter results in **_more uniqueness_,** and a **_lower rate_** of collisions.

For some properties, a certain level of collisions is desirable. In many cases we can satisfy our coverage checks just by adjusting the QC size parameter.

Co-authored-by: Jonathan Knowles <[email protected]>
Co-authored-by: Samuel Evans-Powell <[email protected]>
Co-authored-by: IOHK <[email protected]>

cabal.project

@@ -38,7 +38,7 @@
 --
 --------------------------------------------------------------------------------
 
-index-state: 2022-02-22T20:47:03Z
+index-state: 2022-03-30T00:00:00Z
 with-compiler: ghc-8.10.7
 
 packages:

lib/core/cardano-wallet-core.cabal

@@ -371,6 +371,7 @@ test-suite unit
     , QuickCheck
     , quickcheck-classes
     , quickcheck-state-machine >= 0.6.0
+    , quickcheck-quid
     , quiet
     , random
     , retry