feat(fsharp): m01-m06 util, model, rules, random, spawn, game, view with Expecto tests

Co-Authored-By: Claude Opus 5.5 <[email protected]>

fsharp/tests/Fixtures.fs

@@ -1,9 +1,11 @@
-/// Loads shared fixtures from ../../fixtures/<name>.json.
-/// Typed decoders (point, direction, status, action, state, opt) arrive with the model (Task 13).
+/// Loads shared fixtures from ../fixtures/<name>.json and decodes them into the course's types.
 module Snake.Tests.Fixtures
 
 open System.IO
 open System.Text.Json
+open Expecto
+open Snake.Model
+open Snake.View
 
 let private dir =
     Path.GetFullPath(Path.Combine(Directory.GetCurrentDirectory(), "..", "fixtures"))
@@ -19,3 +21,68 @@ let cases (name: string) : JsonElement list =
 /// Decode a nullable JSON value into an Option.
 let opt (f: JsonElement -> 'a) (v: JsonElement) : 'a option =
     if v.ValueKind = JsonValueKind.Null then None else Some(f v)
+
+let prop (key: string) (v: JsonElement) : JsonElement = v.GetProperty(key)
+let str (v: JsonElement) : string = v.GetString()
+let num (v: JsonElement) : int = v.GetInt32()
+let u32 (v: JsonElement) : uint32 = v.GetUInt32()
+let bool (v: JsonElement) : bool = v.GetBoolean()
+let list (f: JsonElement -> 'a) (v: JsonElement) : 'a list = v.EnumerateArray() |> Seq.map f |> List.ofSeq
+
+/// The i-th argument of a case.
+let arg (i: int) (c: JsonElement) : JsonElement = (prop "args" c)[i]
+let expected (c: JsonElement) : JsonElement = prop "expected" c
+let name (c: JsonElement) : string = str (prop "name" c)
+
+let point (v: JsonElement) : Point = { X = num (prop "x" v); Y = num (prop "y" v) }
+
+let direction (v: JsonElement) : Direction =
+    match str v with
+    | "Up" -> Up
+    | "Down" -> Down
+    | "Left" -> Left
+    | "Right" -> Right
+    | other -> failwith $"unknown direction: {other}"
+
+let status (v: JsonElement) : Status =
+    match str v with
+    | "Playing" -> Playing
+    | "Paused" -> Paused
+    | "GameOver" -> GameOver
+    | "Won" -> Won
+    | other -> failwith $"unknown status: {other}"
+
+let action (v: JsonElement) : Action =
+    match str (prop "tag" v) with
+    | "Tick" -> Tick
+    | "Turn" -> Turn(direction (prop "dir" v))
+    | "TogglePause" -> TogglePause
+    | "Restart" -> Restart
+    | "Frame" -> Frame
+    | other -> failwith $"unknown action tag: {other}"
+
+/// JSON uses camelCase field names; the F# record uses PascalCase.
+let gameState (v: JsonElement) : GameState =
+    { Width = num (prop "width" v)
+      Height = num (prop "height" v)
+      Snake = list point (prop "snake" v)
+      Dir = direction (prop "dir" v)
+      NextDir = direction (prop "nextDir" v)
+      Apple = opt point (prop "apple" v)
+      Seed = u32 (prop "seed" v)
+      Score = num (prop "score" v)
+      Status = status (prop "status" v)
+      Frame = num (prop "frame" v) }
+
+let shape (v: JsonElement) : Shape =
+    let n key = num (prop key v)
+    let s key = str (prop key v)
+
+    match s "tag" with
+    | "Rect" -> Rect(n "x", n "y", n "w", n "h", s "color")
+    | "Text" -> Text(n "x", n "y", s "text", s "color", n "size", s "align")
+    | other -> failwith $"unknown shape tag: {other}"
+
+/// One test per case of a fixture, named "<label>: <case name>".
+let fixtureTests (fixture: string) (label: string) (body: JsonElement -> unit) : Test list =
+    [ for c in cases fixture -> testCase $"{label}: {name c}" (fun () -> body c) ]