feat: NCS-25 Add linters to keep quality up (#27)

Reviewed-on: #27
Reviewed-by: Leon Hermann <lq@blackhole.local>
Co-authored-by: Janis <janis.e.20@gmx.de>
Co-committed-by: Janis <janis.e.20@gmx.de>

modules/core/src/main/scala/de/nowchess/chess/command/Command.scala

@@ -1,11 +1,11 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, Piece}
+import de.nowchess.api.board.{Piece, Square}
 import de.nowchess.api.game.GameContext
 
-/** Marker trait for all commands that can be executed and undone.
- *  Commands encapsulate user actions and game state transitions.
- */
+/** Marker trait for all commands that can be executed and undone. Commands encapsulate user actions and game state
+  * transitions.
+  */
 trait Command:
   /** Execute the command and return true if successful, false otherwise. */
   def execute(): Boolean
@@ -16,15 +16,14 @@ trait Command:
   /** A human-readable description of this command. */
   def description: String
 
-/** Command to move a piece from one square to another.
- *  Stores the move result so undo can restore previous state.
- */
+/** Command to move a piece from one square to another. Stores the move result so undo can restore previous state.
+  */
 case class MoveCommand(
-  from: Square,
-  to: Square,
-  moveResult: Option[MoveResult] = None,
-  previousContext: Option[GameContext] = None,
-  notation: String = ""
+    from: Square,
+    to: Square,
+    moveResult: Option[MoveResult] = None,
+    previousContext: Option[GameContext] = None,
+    notation: String = "",
 ) extends Command:
 
   override def execute(): Boolean =
@@ -39,18 +38,18 @@ case class MoveCommand(
 sealed trait MoveResult
 object MoveResult:
   case class Successful(newContext: GameContext, captured: Option[Piece]) extends MoveResult
-  case object InvalidFormat extends MoveResult
-  case object InvalidMove extends MoveResult
+  case object InvalidFormat                                               extends MoveResult
+  case object InvalidMove                                                 extends MoveResult
 
 /** Command to quit the game. */
 case class QuitCommand() extends Command:
-  override def execute(): Boolean = true
-  override def undo(): Boolean = false
+  override def execute(): Boolean  = true
+  override def undo(): Boolean     = false
   override def description: String = "Quit game"
 
 /** Command to reset the board to initial position. */
 case class ResetCommand(
-  previousContext: Option[GameContext] = None
+    previousContext: Option[GameContext] = None,
 ) extends Command:
 
   override def execute(): Boolean = true

modules/core/src/main/scala/de/nowchess/chess/command/CommandInvoker.scala

@@ -3,21 +3,19 @@ package de.nowchess.chess.command
 /** Manages command execution and history for undo/redo support. */
 class CommandInvoker:
   private val executedCommands = scala.collection.mutable.ListBuffer[Command]()
+  @SuppressWarnings(Array("DisableSyntax.var"))
   private var currentIndex = -1
 
-  /** Execute a command and add it to history.
-   *  Discards any redo history if not at the end of the stack.
-   */
+  /** Execute a command and add it to history. Discards any redo history if not at the end of the stack.
+    */
   def execute(command: Command): Boolean = synchronized {
     if command.execute() then
       // Remove any commands after current index (redo stack is discarded)
-      while currentIndex < executedCommands.size - 1 do
-        executedCommands.remove(executedCommands.size - 1)
+      while currentIndex < executedCommands.size - 1 do executedCommands.remove(executedCommands.size - 1)
       executedCommands += command
       currentIndex += 1
       true
-    else
-      false
+    else false
   }
 
   /** Undo the last executed command if possible. */
@@ -27,10 +25,8 @@ class CommandInvoker:
       if command.undo() then
         currentIndex -= 1
         true
-      else
-        false
-    else
-      false
+      else false
+    else false
   }
 
   /** Redo the next command in history if available. */
@@ -40,10 +36,8 @@ class CommandInvoker:
       if command.execute() then
         currentIndex += 1
         true
-      else
-        false
-    else
-      false
+      else false
+    else false
   }
 
   /** Get the history of all executed commands. */

modules/core/src/main/scala/de/nowchess/chess/controller/Parser.scala

@@ -4,21 +4,25 @@ import de.nowchess.api.board.{File, Rank, Square}
 
 object Parser:
 
-  /** Parses coordinate notation such as "e2e4" or "g1f3".
-   *  Returns None for any input that does not match the expected format.
-   */
+  /** Parses coordinate notation such as "e2e4" or "g1f3". Returns None for any input that does not match the expected
+    * format.
+    */
   def parseMove(input: String): Option[(Square, Square)] =
     val trimmed = input.trim.toLowerCase
-    Option.when(trimmed.length == 4)(trimmed).flatMap: s =>
-      for
-        from <- parseSquare(s.substring(0, 2))
-        to   <- parseSquare(s.substring(2, 4))
-      yield (from, to)
+    Option
+      .when(trimmed.length == 4)(trimmed)
+      .flatMap: s =>
+        for
+          from <- parseSquare(s.substring(0, 2))
+          to   <- parseSquare(s.substring(2, 4))
+        yield (from, to)
 
   private def parseSquare(s: String): Option[Square] =
-    Option.when(s.length == 2)(s).flatMap: sq =>
-      val fileIdx = sq(0) - 'a'
-      val rankIdx = sq(1) - '1'
-      Option.when(fileIdx >= 0 && fileIdx <= 7 && rankIdx >= 0 && rankIdx <= 7)(
-        Square(File.values(fileIdx), Rank.values(rankIdx))
-      )
+    Option
+      .when(s.length == 2)(s)
+      .flatMap: sq =>
+        val fileIdx = sq(0) - 'a'
+        val rankIdx = sq(1) - '1'
+        Option.when(fileIdx >= 0 && fileIdx <= 7 && rankIdx >= 0 && rankIdx <= 7)(
+          Square(File.values(fileIdx), Rank.values(rankIdx)),
+        )

modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala

@@ -6,45 +6,46 @@ import de.nowchess.api.game.GameContext
 import de.nowchess.chess.controller.Parser
 import de.nowchess.chess.observer.*
 import de.nowchess.chess.command.{CommandInvoker, MoveCommand, MoveResult}
-import de.nowchess.io.{GameContextImport, GameContextExport}
+import de.nowchess.io.{GameContextExport, GameContextImport}
 import de.nowchess.rules.RuleSet
 import de.nowchess.rules.sets.DefaultRules
 
-/** Pure game engine that manages game state and notifies observers of state changes.
- *  All rule queries delegate to the injected RuleSet.
- *  All user interactions go through Commands; state changes are broadcast via GameEvents.
- */
+/** Pure game engine that manages game state and notifies observers of state changes. All rule queries delegate to the
+  * injected RuleSet. All user interactions go through Commands; state changes are broadcast via GameEvents.
+  */
 class GameEngine(
-  val initialContext: GameContext = GameContext.initial,
-  val ruleSet: RuleSet = DefaultRules
+    val initialContext: GameContext = GameContext.initial,
+    val ruleSet: RuleSet = DefaultRules,
 ) extends Observable:
+  @SuppressWarnings(Array("DisableSyntax.var"))
   private var currentContext: GameContext = initialContext
-  private val invoker = new CommandInvoker()
+  private val invoker                     = new CommandInvoker()
 
   /** Pending promotion: the Move that triggered it (from/to only, moveType filled in later). */
   private case class PendingPromotion(from: Square, to: Square, contextBefore: GameContext)
+  @SuppressWarnings(Array("DisableSyntax.var"))
   private var pendingPromotion: Option[PendingPromotion] = None
 
   /** True if a pawn promotion move is pending and needs a piece choice. */
-  def isPendingPromotion: Boolean = synchronized { pendingPromotion.isDefined }
+  def isPendingPromotion: Boolean = synchronized(pendingPromotion.isDefined)
 
   // Synchronized accessors for current state
-  def board: Board   = synchronized { currentContext.board }
-  def turn: Color    = synchronized { currentContext.turn }
-  def context: GameContext = synchronized { currentContext }
+  def board: Board         = synchronized(currentContext.board)
+  def turn: Color          = synchronized(currentContext.turn)
+  def context: GameContext = synchronized(currentContext)
 
   /** Check if undo is available. */
-  def canUndo: Boolean = synchronized { invoker.canUndo }
+  def canUndo: Boolean = synchronized(invoker.canUndo)
 
   /** Check if redo is available. */
-  def canRedo: Boolean = synchronized { invoker.canRedo }
+  def canRedo: Boolean = synchronized(invoker.canRedo)
 
   /** Get the command history for inspection (testing/debugging). */
-  def commandHistory: List[de.nowchess.chess.command.Command] = synchronized { invoker.history }
+  def commandHistory: List[de.nowchess.chess.command.Command] = synchronized(invoker.history)
 
-  /** Process a raw move input string and update game state if valid.
-   *  Notifies all observers of the outcome via GameEvent.
-   */
+  /** Process a raw move input string and update game state if valid. Notifies all observers of the outcome via
+    * GameEvent.
+    */
   def processUserInput(rawInput: String): Unit = synchronized {
     val trimmed = rawInput.trim.toLowerCase
     trimmed match
@@ -62,10 +63,12 @@ class GameEngine(
           invoker.clear()
           notifyObservers(DrawClaimedEvent(currentContext))
         else
-          notifyObservers(InvalidMoveEvent(
-            currentContext,
-            "Draw cannot be claimed: the 50-move rule has not been triggered."
-          ))
+          notifyObservers(
+            InvalidMoveEvent(
+              currentContext,
+              "Draw cannot be claimed: the 50-move rule has not been triggered.",
+            ),
+          )
 
       case "" =>
         notifyObservers(InvalidMoveEvent(currentContext, "Please enter a valid move or command."))
@@ -73,10 +76,12 @@ class GameEngine(
       case moveInput =>
         Parser.parseMove(moveInput) match
           case None =>
-            notifyObservers(InvalidMoveEvent(
-              currentContext,
-              s"Invalid move format '$moveInput'. Use coordinate notation, e.g. e2e4."
-            ))
+            notifyObservers(
+              InvalidMoveEvent(
+                currentContext,
+                s"Invalid move format '$moveInput'. Use coordinate notation, e.g. e2e4.",
+              ),
+            )
           case Some((from, to)) =>
             handleParsedMove(from, to)
   }
@@ -108,9 +113,8 @@ class GameEngine(
       to.rank.ordinal == promoRank
     }
 
-  /** Apply a player's promotion piece choice.
-   *  Must only be called when isPendingPromotion is true.
-   */
+  /** Apply a player's promotion piece choice. Must only be called when isPendingPromotion is true.
+    */
   def completePromotion(piece: PromotionPiece): Unit = synchronized {
     pendingPromotion match
       case None =>
@@ -120,23 +124,19 @@ class GameEngine(
         val move = Move(pending.from, pending.to, MoveType.Promotion(piece))
         // Verify it's actually legal
         val legal = ruleSet.legalMoves(currentContext)(pending.from)
-        if legal.contains(move) then
-          executeMove(move)
-        else
-          notifyObservers(InvalidMoveEvent(currentContext, "Error completing promotion."))
+        if legal.contains(move) then executeMove(move)
+        else notifyObservers(InvalidMoveEvent(currentContext, "Error completing promotion."))
   }
 
   /** Undo the last move. */
-  def undo(): Unit = synchronized { performUndo() }
+  def undo(): Unit = synchronized(performUndo())
 
   /** Redo the last undone move. */
-  def redo(): Unit = synchronized { performRedo() }
+  def redo(): Unit = synchronized(performRedo())
 
-  /** Load a game using the provided importer.
-   *  If the imported context has moves, they are replayed through the command system.
-   *  Otherwise, the position is set directly.
-   *  Notifies observers with PgnLoadedEvent on success.
-   */
+  /** Load a game using the provided importer. If the imported context has moves, they are replayed through the command
+    * system. Otherwise, the position is set directly. Notifies observers with PgnLoadedEvent on success.
+    */
   def loadGame(importer: GameContextImport, input: String): Either[String, Unit] = synchronized {
     importer.importGameContext(input) match
       case Left(err) => Left(err)
@@ -155,29 +155,24 @@ class GameEngine(
     if ctx.moves.isEmpty then
       currentContext = ctx
       Right(())
-    else
-      replayMoves(ctx.moves, savedContext)
+    else replayMoves(ctx.moves, savedContext)
 
   private[engine] def replayMoves(moves: List[Move], savedContext: GameContext): Either[String, Unit] =
-    var error: Option[String] = None
-    moves.foreach: move =>
-      if error.isEmpty then
-        handleParsedMove(move.from, move.to)
+    val result = moves.foldLeft[Either[String, Unit]](Right(())) { (acc, move) =>
+      acc.flatMap(_ => applyReplayMove(move))
+    }
+    result.left.foreach(_ => currentContext = savedContext)
+    result
 
-        move.moveType match {
-          case MoveType.Promotion(pp) =>
-            if pendingPromotion.isDefined then
-              completePromotion(pp)
-            else
-              error = Some(s"Promotion required for move ${move.from}${move.to}")
-          case _ => ()
-        }
-    error match
-      case Some(err) =>
-        currentContext = savedContext
-        Left(err)
-      case None =>
+  private def applyReplayMove(move: Move): Either[String, Unit] =
+    handleParsedMove(move.from, move.to)
+    move.moveType match
+      case MoveType.Promotion(pp) if pendingPromotion.isDefined =>
+        completePromotion(pp)
         Right(())
+      case MoveType.Promotion(_) =>
+        Left(s"Promotion required for move ${move.from}${move.to}")
+      case _ => Right(())
 
   /** Export the current game context using the provided exporter. */
   def exportGame(exporter: GameContextExport): String = synchronized {
@@ -203,25 +198,27 @@ class GameEngine(
 
   private def executeMove(move: Move): Unit =
     val contextBefore = currentContext
-    val nextContext = ruleSet.applyMove(currentContext)(move)
-    val captured = computeCaptured(currentContext, move)
+    val nextContext   = ruleSet.applyMove(currentContext)(move)
+    val captured      = computeCaptured(currentContext, move)
 
     val cmd = MoveCommand(
       from = move.from,
       to = move.to,
       moveResult = Some(MoveResult.Successful(nextContext, captured)),
       previousContext = Some(contextBefore),
-      notation = translateMoveToNotation(move, contextBefore.board)
+      notation = translateMoveToNotation(move, contextBefore.board),
     )
     invoker.execute(cmd)
     currentContext = nextContext
 
-    notifyObservers(MoveExecutedEvent(
-      currentContext,
-      move.from.toString,
-      move.to.toString,
-      captured.map(c => s"${c.color.label} ${c.pieceType.label}")
-    ))
+    notifyObservers(
+      MoveExecutedEvent(
+        currentContext,
+        move.from.toString,
+        move.to.toString,
+        captured.map(c => s"${c.color.label} ${c.pieceType.label}"),
+      ),
+    )
 
     if ruleSet.isCheckmate(currentContext) then
       val winner = currentContext.turn.opposite
@@ -232,18 +229,16 @@ class GameEngine(
       notifyObservers(StalemateEvent(currentContext))
       invoker.clear()
       currentContext = GameContext.initial
-    else if ruleSet.isCheck(currentContext) then
-      notifyObservers(CheckDetectedEvent(currentContext))
+    else if ruleSet.isCheck(currentContext) then notifyObservers(CheckDetectedEvent(currentContext))
 
-    if currentContext.halfMoveClock >= 100 then
-      notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
+    if currentContext.halfMoveClock >= 100 then notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
 
   private def translateMoveToNotation(move: Move, boardBefore: Board): String =
     move.moveType match
-      case MoveType.CastleKingside  => "O-O"
-      case MoveType.CastleQueenside => "O-O-O"
-      case MoveType.EnPassant   => enPassantNotation(move)
-      case MoveType.Promotion(pp) => promotionNotation(move, pp)
+      case MoveType.CastleKingside    => "O-O"
+      case MoveType.CastleQueenside   => "O-O-O"
+      case MoveType.EnPassant         => enPassantNotation(move)
+      case MoveType.Promotion(pp)     => promotionNotation(move, pp)
       case MoveType.Normal(isCapture) => normalMoveNotation(move, boardBefore, isCapture)
 
   private def enPassantNotation(move: Move): String =
@@ -295,8 +290,7 @@ class GameEngine(
           moveCmd.previousContext.foreach(currentContext = _)
           invoker.undo()
           notifyObservers(MoveUndoneEvent(currentContext, moveCmd.notation))
-    else
-      notifyObservers(InvalidMoveEvent(currentContext, "Nothing to undo."))
+    else notifyObservers(InvalidMoveEvent(currentContext, "Nothing to undo."))
 
   private def performRedo(): Unit =
     if invoker.canRedo then
@@ -307,12 +301,13 @@ class GameEngine(
             currentContext = nextCtx
             invoker.redo()
             val capturedDesc = cap.map(c => s"${c.color.label} ${c.pieceType.label}")
-            notifyObservers(MoveRedoneEvent(
-              currentContext,
-              moveCmd.notation,
-              moveCmd.from.toString,
-              moveCmd.to.toString,
-              capturedDesc
-            ))
-    else
-      notifyObservers(InvalidMoveEvent(currentContext, "Nothing to redo."))
+            notifyObservers(
+              MoveRedoneEvent(
+                currentContext,
+                moveCmd.notation,
+                moveCmd.from.toString,
+                moveCmd.to.toString,
+                capturedDesc,
+              ),
+            )
+    else notifyObservers(InvalidMoveEvent(currentContext, "Nothing to redo."))

modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala

@@ -3,82 +3,81 @@ package de.nowchess.chess.observer
 import de.nowchess.api.board.{Color, Square}
 import de.nowchess.api.game.GameContext
 
-/** Base trait for all game state events.
- *  Events are immutable snapshots of game state changes.
- */
+/** Base trait for all game state events. Events are immutable snapshots of game state changes.
+  */
 sealed trait GameEvent:
   def context: GameContext
 
 /** Fired when a move is successfully executed. */
 case class MoveExecutedEvent(
-  context: GameContext,
-  fromSquare: String,
-  toSquare: String,
-  capturedPiece: Option[String]
+    context: GameContext,
+    fromSquare: String,
+    toSquare: String,
+    capturedPiece: Option[String],
 ) extends GameEvent
 
 /** Fired when the current player is in check. */
 case class CheckDetectedEvent(
-  context: GameContext
+    context: GameContext,
 ) extends GameEvent
 
 /** Fired when the game reaches checkmate. */
 case class CheckmateEvent(
-  context: GameContext,
-  winner: Color
+    context: GameContext,
+    winner: Color,
 ) extends GameEvent
 
 /** Fired when the game reaches stalemate. */
 case class StalemateEvent(
-  context: GameContext
+    context: GameContext,
 ) extends GameEvent
 
 /** Fired when a move is invalid. */
 case class InvalidMoveEvent(
-  context: GameContext,
-  reason: String
+    context: GameContext,
+    reason: String,
 ) extends GameEvent
 
 /** Fired when a pawn reaches the back rank and the player must choose a promotion piece. */
 case class PromotionRequiredEvent(
-  context: GameContext,
-  from: Square,
-  to: Square
+    context: GameContext,
+    from: Square,
+    to: Square,
 ) extends GameEvent
 
 /** Fired when the board is reset. */
 case class BoardResetEvent(
-  context: GameContext
+    context: GameContext,
 ) extends GameEvent
 
 /** Fired after any move where the half-move clock reaches 100 — the 50-move rule is now claimable. */
 case class FiftyMoveRuleAvailableEvent(
-  context: GameContext
+    context: GameContext,
 ) extends GameEvent
 
 /** Fired when a player successfully claims a draw under the 50-move rule. */
 case class DrawClaimedEvent(
-  context: GameContext
+    context: GameContext,
 ) extends GameEvent
 
 /** Fired when a move is undone, carrying PGN notation of the reversed move. */
 case class MoveUndoneEvent(
-  context: GameContext,
-  pgnNotation: String
+    context: GameContext,
+    pgnNotation: String,
 ) extends GameEvent
 
 /** Fired when a previously undone move is redone, carrying PGN notation of the replayed move. */
 case class MoveRedoneEvent(
-  context: GameContext,
-  pgnNotation: String,
-  fromSquare: String,
-  toSquare: String,
-  capturedPiece: Option[String]
+    context: GameContext,
+    pgnNotation: String,
+    fromSquare: String,
+    toSquare: String,
+    capturedPiece: Option[String],
 ) extends GameEvent
 
 /** Fired after a PGN string is successfully loaded and all moves are replayed into history. */
 case class PgnLoadedEvent(
-  context: GameContext
+    context: GameContext,
 ) extends GameEvent
 
 /** Observer trait: implement to receive game state updates. */

modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerBranchTest.scala

@@ -1,6 +1,6 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, File, Rank}
+import de.nowchess.api.board.{File, Rank, Square}
 import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -10,13 +10,16 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
   private def sq(f: File, r: Rank): Square = Square(f, r)
 
   private case class FailingCommand() extends Command:
-    override def execute(): Boolean = false
-    override def undo(): Boolean = false
+    override def execute(): Boolean  = false
+    override def undo(): Boolean     = false
     override def description: String = "Failing command"
 
-  private case class ConditionalFailCommand(var shouldFailOnUndo: Boolean = false, var shouldFailOnExecute: Boolean = false) extends Command:
-    override def execute(): Boolean = !shouldFailOnExecute
-    override def undo(): Boolean = !shouldFailOnUndo
+  private case class ConditionalFailCommand(
+      var shouldFailOnUndo: Boolean = false,
+      var shouldFailOnExecute: Boolean = false,
+  ) extends Command:
+    override def execute(): Boolean  = !shouldFailOnExecute
+    override def undo(): Boolean     = !shouldFailOnUndo
     override def description: String = "Conditional fail"
 
   private def createMoveCommand(from: Square, to: Square, executeSucceeds: Boolean = true): MoveCommand =
@@ -24,12 +27,12 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
       from = from,
       to = to,
       moveResult = if executeSucceeds then Some(MoveResult.Successful(GameContext.initial, None)) else None,
-      previousContext = Some(GameContext.initial)
+      previousContext = Some(GameContext.initial),
     )
 
   test("execute rejects failing commands and keeps history unchanged"):
     val invoker = new CommandInvoker()
-    val cmd = FailingCommand()
+    val cmd     = FailingCommand()
     invoker.execute(cmd) shouldBe false
     invoker.history.size shouldBe 0
     invoker.getCurrentIndex shouldBe -1
@@ -52,8 +55,8 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
 
     {
       val invoker = new CommandInvoker()
-      val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-      val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
+      val cmd1    = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val cmd2    = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
       invoker.execute(cmd1)
       invoker.execute(cmd2)
       invoker.undo()
@@ -62,7 +65,7 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
     }
 
     {
-      val invoker = new CommandInvoker()
+      val invoker        = new CommandInvoker()
       val failingUndoCmd = ConditionalFailCommand(shouldFailOnUndo = true)
       invoker.execute(failingUndoCmd) shouldBe true
       invoker.canUndo shouldBe true
@@ -71,7 +74,7 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
     }
 
     {
-      val invoker = new CommandInvoker()
+      val invoker        = new CommandInvoker()
       val successUndoCmd = ConditionalFailCommand()
       invoker.execute(successUndoCmd) shouldBe true
       invoker.undo() shouldBe true
@@ -85,15 +88,15 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
 
     {
       val invoker = new CommandInvoker()
-      val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
       invoker.execute(cmd)
       invoker.canRedo shouldBe false
       invoker.redo() shouldBe false
     }
 
     {
-      val invoker = new CommandInvoker()
-      val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val invoker     = new CommandInvoker()
+      val cmd1        = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
       val redoFailCmd = ConditionalFailCommand()
       invoker.execute(cmd1)
       invoker.execute(redoFailCmd)
@@ -106,7 +109,7 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
 
     {
       val invoker = new CommandInvoker()
-      val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
       invoker.execute(cmd) shouldBe true
       invoker.undo() shouldBe true
       invoker.redo() shouldBe true
@@ -115,9 +118,9 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
 
     {
       val invoker = new CommandInvoker()
-      val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-      val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-      val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
+      val cmd1    = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val cmd2    = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
+      val cmd3    = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
       invoker.execute(cmd1)
       invoker.execute(cmd2)
       invoker.undo()
@@ -130,10 +133,10 @@ class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
 
     {
       val invoker = new CommandInvoker()
-      val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-      val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-      val cmd3 = createMoveCommand(sq(File.G, Rank.R1), sq(File.F, Rank.R3))
-      val cmd4 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
+      val cmd1    = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+      val cmd2    = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
+      val cmd3    = createMoveCommand(sq(File.G, Rank.R1), sq(File.F, Rank.R3))
+      val cmd4    = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
       invoker.execute(cmd1)
       invoker.execute(cmd2)
       invoker.execute(cmd3)

modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerTest.scala

@@ -1,6 +1,6 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, File, Rank}
+import de.nowchess.api.board.{File, Rank, Square}
 import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -14,12 +14,12 @@ class CommandInvokerTest extends AnyFunSuite with Matchers:
       from = from,
       to = to,
       moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
-      previousContext = Some(GameContext.initial)
+      previousContext = Some(GameContext.initial),
     )
 
   test("execute appends commands and updates index"):
     val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+    val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     invoker.execute(cmd) shouldBe true
     invoker.history.size shouldBe 1
     invoker.getCurrentIndex shouldBe 0
@@ -31,7 +31,7 @@ class CommandInvokerTest extends AnyFunSuite with Matchers:
 
   test("undo and redo update index and availability flags"):
     val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+    val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     invoker.canUndo shouldBe false
     invoker.execute(cmd)
     invoker.canUndo shouldBe true
@@ -43,7 +43,7 @@ class CommandInvokerTest extends AnyFunSuite with Matchers:
 
   test("clear removes full history and resets index"):
     val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+    val cmd     = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
     invoker.execute(cmd)
     invoker.clear()
     invoker.history.size shouldBe 0
@@ -51,9 +51,9 @@ class CommandInvokerTest extends AnyFunSuite with Matchers:
 
   test("execute after undo discards redo history"):
     val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
+    val cmd1    = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
+    val cmd2    = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
+    val cmd3    = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
     invoker.execute(cmd1)
     invoker.execute(cmd2)
     invoker.undo()

modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandTest.scala

@@ -1,6 +1,6 @@
 package de.nowchess.chess.command
 
-import de.nowchess.api.board.{Square, File, Rank}
+import de.nowchess.api.board.{File, Rank, Square}
 import de.nowchess.api.game.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -21,7 +21,7 @@ class MoveCommandTest extends AnyFunSuite with Matchers:
     val executable = MoveCommand(
       from = sq(File.E, Rank.R2),
       to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(GameContext.initial, None))
+      moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
     )
     executable.execute() shouldBe true
 
@@ -29,7 +29,7 @@ class MoveCommandTest extends AnyFunSuite with Matchers:
       from = sq(File.E, Rank.R2),
       to = sq(File.E, Rank.R4),
       moveResult = Some(MoveResult.Successful(GameContext.initial, None)),
-      previousContext = Some(GameContext.initial)
+      previousContext = Some(GameContext.initial),
     )
     undoable.undo() shouldBe true
 
@@ -39,7 +39,7 @@ class MoveCommandTest extends AnyFunSuite with Matchers:
     val result = MoveResult.Successful(GameContext.initial, None)
     val cmd2 = cmd1.copy(
       moveResult = Some(result),
-      previousContext = Some(GameContext.initial)
+      previousContext = Some(GameContext.initial),
     )
 
     cmd1.moveResult shouldBe None
@@ -52,14 +52,14 @@ class MoveCommandTest extends AnyFunSuite with Matchers:
       from = sq(File.E, Rank.R2),
       to = sq(File.E, Rank.R4),
       moveResult = None,
-      previousContext = None
+      previousContext = None,
     )
 
     val eq2 = MoveCommand(
       from = sq(File.E, Rank.R2),
       to = sq(File.E, Rank.R4),
       moveResult = None,
-      previousContext = None
+      previousContext = None,
     )
 
     eq1 shouldBe eq2

modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala

@@ -27,7 +27,7 @@ object EngineTestHelpers:
     private val _events = mutable.ListBuffer[GameEvent]()
 
     def events: mutable.ListBuffer[GameEvent] = _events
-    def eventCount: Int = _events.length
+    def eventCount: Int                       = _events.length
     def hasEvent[T <: GameEvent](implicit ct: scala.reflect.ClassTag[T]): Boolean =
       _events.exists(ct.runtimeClass.isInstance(_))
     def getEvent[T <: GameEvent](implicit ct: scala.reflect.ClassTag[T]): Option[T] =

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala

@@ -2,7 +2,7 @@ package de.nowchess.chess.engine
 
 import scala.collection.mutable
 import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.observer.{Observer, GameEvent, CheckDetectedEvent, CheckmateEvent, StalemateEvent}
+import de.nowchess.chess.observer.{CheckDetectedEvent, CheckmateEvent, GameEvent, Observer, StalemateEvent}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -10,82 +10,91 @@ import org.scalatest.matchers.should.Matchers
 class GameEngineGameEndingTest extends AnyFunSuite with Matchers:
 
   test("GameEngine handles Checkmate (Fool's Mate)"):
-    val engine = new GameEngine()
+    val engine   = new GameEngine()
     val observer = new EndingMockObserver()
     engine.subscribe(observer)
-    
+
     // Play Fool's mate
     engine.processUserInput("f2f3")
     engine.processUserInput("e7e5")
     engine.processUserInput("g2g4")
-    
+
     observer.events.clear()
     engine.processUserInput("d8h4")
 
     // Verify CheckmateEvent (engine also fires MoveExecutedEvent before CheckmateEvent)
     observer.events.last shouldBe a[CheckmateEvent]
-    
+
     val event = observer.events.last.asInstanceOf[CheckmateEvent]
     event.winner shouldBe Color.Black
-    
+
     // Board should be reset after checkmate
     engine.board shouldBe Board.initial
     engine.turn shouldBe Color.White
 
   test("GameEngine handles check detection"):
-    val engine = new GameEngine()
+    val engine   = new GameEngine()
     val observer = new EndingMockObserver()
     engine.subscribe(observer)
-    
+
     // Play a simple check
     engine.processUserInput("e2e4")
     engine.processUserInput("e7e5")
     engine.processUserInput("f1c4")
     engine.processUserInput("g8f6")
-    
+
     observer.events.clear()
     engine.processUserInput("c4f7") // Check!
-    
+
     val checkEvents = observer.events.collect { case e: CheckDetectedEvent => e }
     checkEvents.size shouldBe 1
     checkEvents.head.context.turn shouldBe Color.Black // Black is now in check
-    
+
   // Shortest known stalemate is 19 moves. Here is a faster one:
   // e3 a5 Qh5 Ra6 Qxa5 h5 h4 Rah6 Qxc7 f6 Qxd7+ Kf7 Qxb7 Qd3 Qxb8 Qh7 Qxc8 Kg6 Qe6
   // Wait, let's just use Sam Loyd's 10-move stalemate:
   // 1. e3 a5 2. Qh5 Ra6 3. Qxa5 h5 4. h4 Rah6 5. Qxc7 f6 6. Qxd7+ Kf7 7. Qxb7 Qd3 8. Qxb8 Qh7 9. Qxc8 Kg6 10. Qe6
   test("GameEngine handles Stalemate via 10-move known sequence"):
-    val engine = new GameEngine()
+    val engine   = new GameEngine()
     val observer = new EndingMockObserver()
     engine.subscribe(observer)
-    
+
     val moves = List(
-      "e2e3", "a7a5",
-      "d1h5", "a8a6",
-      "h5a5", "h7h5",
-      "h2h4", "a6h6",
-      "a5c7", "f7f6",
-      "c7d7", "e8f7",
-      "d7b7", "d8d3",
-      "b7b8", "d3h7",
-      "b8c8", "f7g6",
-      "c8e6"
+      "e2e3",
+      "a7a5",
+      "d1h5",
+      "a8a6",
+      "h5a5",
+      "h7h5",
+      "h2h4",
+      "a6h6",
+      "a5c7",
+      "f7f6",
+      "c7d7",
+      "e8f7",
+      "d7b7",
+      "d8d3",
+      "b7b8",
+      "d3h7",
+      "b8c8",
+      "f7g6",
+      "c8e6",
     )
-    
+
     moves.dropRight(1).foreach(engine.processUserInput)
-    
+
     observer.events.clear()
     engine.processUserInput(moves.last)
-    
+
     val stalemateEvents = observer.events.collect { case e: StalemateEvent => e }
     stalemateEvents.size shouldBe 1
-    
+
     // Board should be reset after stalemate
     engine.board shouldBe Board.initial
     engine.turn shouldBe Color.White
 
 private class EndingMockObserver extends Observer:
   val events = mutable.ListBuffer[GameEvent]()
-  
+
   override def onGameEvent(event: GameEvent): Unit =
-    events += event
+    events += event

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala

@@ -92,12 +92,12 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
       def candidateMoves(context: GameContext)(square: Square): List[Move] = legalMoves(context)(square)
       def legalMoves(context: GameContext)(square: Square): List[Move] =
         if square == sq("e2") then List(promotionMove) else List.empty
-      def allLegalMoves(context: GameContext): List[Move] = List(promotionMove)
-      def isCheck(context: GameContext): Boolean = false
-      def isCheckmate(context: GameContext): Boolean = false
-      def isStalemate(context: GameContext): Boolean = false
-      def isInsufficientMaterial(context: GameContext): Boolean = false
-      def isFiftyMoveRule(context: GameContext): Boolean = false
+      def allLegalMoves(context: GameContext): List[Move]          = List(promotionMove)
+      def isCheck(context: GameContext): Boolean                   = false
+      def isCheckmate(context: GameContext): Boolean               = false
+      def isStalemate(context: GameContext): Boolean               = false
+      def isInsufficientMaterial(context: GameContext): Boolean    = false
+      def isFiftyMoveRule(context: GameContext): Boolean           = false
       def applyMove(context: GameContext)(move: Move): GameContext = DefaultRules.applyMove(context)(move)
 
     val engine = new GameEngine(ruleSet = permissiveRules)
@@ -112,14 +112,14 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
     val promotionMove = Move(sq("e2"), sq("e8"), MoveType.Promotion(PromotionPiece.Queen))
     val noLegalMoves = new RuleSet:
       def candidateMoves(context: GameContext)(square: Square): List[Move] = List.empty
-      def legalMoves(context: GameContext)(square: Square): List[Move] = List.empty
-      def allLegalMoves(context: GameContext): List[Move] = List.empty
-      def isCheck(context: GameContext): Boolean = false
-      def isCheckmate(context: GameContext): Boolean = false
-      def isStalemate(context: GameContext): Boolean = false
-      def isInsufficientMaterial(context: GameContext): Boolean = false
-      def isFiftyMoveRule(context: GameContext): Boolean = false
-      def applyMove(context: GameContext)(move: Move): GameContext = context
+      def legalMoves(context: GameContext)(square: Square): List[Move]     = List.empty
+      def allLegalMoves(context: GameContext): List[Move]                  = List.empty
+      def isCheck(context: GameContext): Boolean                           = false
+      def isCheckmate(context: GameContext): Boolean                       = false
+      def isStalemate(context: GameContext): Boolean                       = false
+      def isInsufficientMaterial(context: GameContext): Boolean            = false
+      def isFiftyMoveRule(context: GameContext): Boolean                   = false
+      def applyMove(context: GameContext)(move: Move): GameContext         = context
 
     val engine = new GameEngine(ruleSet = noLegalMoves)
     engine.processUserInput("e2e4")
@@ -137,21 +137,20 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
 
   test("loadGame replay executes non-promotion moves through default replay branch"):
     val normalMove = Move(sq("e2"), sq("e4"), MoveType.Normal())
-    val engine = new GameEngine()
+    val engine     = new GameEngine()
 
     engine.replayMoves(List(normalMove), engine.context) shouldBe Right(())
     engine.context.moves.lastOption shouldBe Some(normalMove)
 
   test("replayMoves skips later moves after the first move triggers an error"):
-    val engine = new GameEngine()
-    val saved = engine.context
+    val engine           = new GameEngine()
+    val saved            = engine.context
     val illegalPromotion = Move(sq("e2"), sq("e1"), MoveType.Promotion(PromotionPiece.Queen))
-    val trailingMove = Move(sq("e2"), sq("e4"))
+    val trailingMove     = Move(sq("e2"), sq("e4"))
 
     engine.replayMoves(List(illegalPromotion, trailingMove), saved) shouldBe Left("Promotion required for move e2e1")
     engine.context shouldBe saved
 
-
   test("normalMoveNotation handles missing source piece"):
     val engine = new GameEngine()
     val result = engine.normalMoveNotation(Move(sq("e3"), sq("e4")), Board.initial, isCapture = false)
@@ -174,5 +173,3 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
     engine.observerCount shouldBe 1
     engine.unsubscribe(observer)
     engine.observerCount shouldBe 0
-
-

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadGameTest.scala

@@ -3,7 +3,7 @@ package de.nowchess.chess.engine
 import scala.collection.mutable
 import de.nowchess.api.board.{Board, Color}
 import de.nowchess.api.game.GameContext
-import de.nowchess.chess.observer.{Observer, GameEvent, PgnLoadedEvent}
+import de.nowchess.chess.observer.{GameEvent, Observer, PgnLoadedEvent}
 import de.nowchess.io.pgn.PgnParser
 import de.nowchess.io.fen.FenParser
 import de.nowchess.io.pgn.PgnExporter
@@ -15,7 +15,7 @@ class GameEngineLoadGameTest extends AnyFunSuite with Matchers:
 
   test("loadGame with PgnParser: loads valid PGN and enables undo/redo"):
     val engine = new GameEngine()
-    val pgn = "[Event \"Test\"]\n\n1. e4 e5\n"
+    val pgn    = "[Event \"Test\"]\n\n1. e4 e5\n"
     val result = engine.loadGame(PgnParser, pgn)
     result shouldBe Right(())
     engine.context.moves.size shouldBe 2
@@ -23,7 +23,7 @@ class GameEngineLoadGameTest extends AnyFunSuite with Matchers:
 
   test("loadGame with FenParser: loads position without replaying moves"):
     val engine = new GameEngine()
-    val fen = "8/4P3/4k3/8/8/8/8/8 w - - 0 1"
+    val fen    = "8/4P3/4k3/8/8/8/8/8 w - - 0 1"
     val result = engine.loadGame(FenParser, fen)
     result shouldBe Right(())
     engine.context.moves.isEmpty shouldBe true

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineNotationTest.scala

@@ -9,11 +9,11 @@ import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
 /** Tests that exercise moveToPgn branches not covered by other test files:
- *  - CastleQueenside (line 223)
- *  - EnPassant notation (lines 224-225) and computeCaptured EnPassant (lines 254-255)
- *  - Promotion(Bishop) notation (line 230)
- *  - King normal move notation (line 246)
- */
+  *   - CastleQueenside (line 223)
+  *   - EnPassant notation (lines 224-225) and computeCaptured EnPassant (lines 254-255)
+  *   - Promotion(Bishop) notation (line 230)
+  *   - King normal move notation (line 246)
+  */
 class GameEngineNotationTest extends AnyFunSuite with Matchers:
 
   private def captureEvents(engine: GameEngine): collection.mutable.ListBuffer[GameEvent] =
@@ -28,10 +28,10 @@ class GameEngineNotationTest extends AnyFunSuite with Matchers:
     val board = FenParser.parseBoard("k7/8/8/8/8/8/8/R3K3").get
     // Castling rights: white queen-side only (no king-side rook present)
     val castlingRights = de.nowchess.api.board.CastlingRights(
-      whiteKingSide  = false,
+      whiteKingSide = false,
       whiteQueenSide = true,
-      blackKingSide  = false,
-      blackQueenSide = false
+      blackKingSide = false,
+      blackQueenSide = false,
     )
     val ctx = GameContext.initial
       .withBoard(board)
@@ -43,7 +43,7 @@ class GameEngineNotationTest extends AnyFunSuite with Matchers:
 
     // White castles queenside: e1c1
     engine.processUserInput("e1c1")
-    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be (true)
+    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be(true)
 
     events.clear()
     engine.undo()
@@ -55,7 +55,7 @@ class GameEngineNotationTest extends AnyFunSuite with Matchers:
 
   test("undo after en passant emits MoveUndoneEvent with file-x-destination notation"):
     // White pawn on e5, black pawn on d5 (just double-pushed), en passant square d6
-    val board = FenParser.parseBoard("k7/8/8/3pP3/8/8/8/7K").get
+    val board    = FenParser.parseBoard("k7/8/8/3pP3/8/8/8/7K").get
     val epSquare = Square.fromAlgebraic("d6")
     val ctx = GameContext.initial
       .withBoard(board)
@@ -68,12 +68,12 @@ class GameEngineNotationTest extends AnyFunSuite with Matchers:
 
     // White pawn on e5 captures en passant to d6
     engine.processUserInput("e5d6")
-    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be (true)
+    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be(true)
 
     // Verify the captured pawn was found (computeCaptured EnPassant branch)
     val moveEvt = events.collect { case e: MoveExecutedEvent => e }.head
     moveEvt.capturedPiece shouldBe defined
-    moveEvt.capturedPiece.get should include ("Black")
+    moveEvt.capturedPiece.get should include("Black")
 
     events.clear()
     engine.undo()
@@ -117,11 +117,11 @@ class GameEngineNotationTest extends AnyFunSuite with Matchers:
 
     // King moves e1 -> f1
     engine.processUserInput("e1f1")
-    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be (true)
+    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be(true)
 
     events.clear()
     engine.undo()
 
     val evt = events.collect { case e: MoveUndoneEvent => e }.head
-    evt.pgnNotation should startWith ("K")
-    evt.pgnNotation should include ("f1")
+    evt.pgnNotation should startWith("K")
+    evt.pgnNotation should include("f1")

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineOutcomesTest.scala

@@ -10,7 +10,7 @@ class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
   // ── Checkmate ───────────────────────────────────────────────────
 
   test("checkmate ends game with CheckmateEvent"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -24,7 +24,7 @@ class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
     observer.hasEvent[CheckmateEvent] shouldBe true
 
   test("checkmate with white winner"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -45,20 +45,29 @@ class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
   // ── Stalemate ───────────────────────────────────────────────────
 
   test("stalemate ends game with StalemateEvent"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
     val moves = List(
-      "e2e3", "a7a5",
-      "d1h5", "a8a6",
-      "h5a5", "h7h5",
-      "h2h4", "a6h6",
-      "a5c7", "f7f6",
-      "c7d7", "e8f7",
-      "d7b7", "d8d3",
-      "b7b8", "d3h7",
-      "b8c8", "f7g6"
+      "e2e3",
+      "a7a5",
+      "d1h5",
+      "a8a6",
+      "h5a5",
+      "h7h5",
+      "h2h4",
+      "a6h6",
+      "a5c7",
+      "f7f6",
+      "c7d7",
+      "e8f7",
+      "d7b7",
+      "d8d3",
+      "b7b8",
+      "d3h7",
+      "b8c8",
+      "f7g6",
     )
     moves.foreach(engine.processUserInput)
     observer.clear()
@@ -68,21 +77,30 @@ class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
     observer.hasEvent[StalemateEvent] shouldBe true
 
   test("stalemate when king has no moves and no pieces"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
     val moves = List(
-      "e2e3", "a7a5",
-      "d1h5", "a8a6",
-      "h5a5", "h7h5",
-      "h2h4", "a6h6",
-      "a5c7", "f7f6",
-      "c7d7", "e8f7",
-      "d7b7", "d8d3",
-      "b7b8", "d3h7",
-      "b8c8", "f7g6",
-      "c8e6"
+      "e2e3",
+      "a7a5",
+      "d1h5",
+      "a8a6",
+      "h5a5",
+      "h7h5",
+      "h2h4",
+      "a6h6",
+      "a5c7",
+      "f7f6",
+      "c7d7",
+      "e8f7",
+      "d7b7",
+      "d8d3",
+      "b7b8",
+      "d3h7",
+      "b8c8",
+      "f7g6",
+      "c8e6",
     )
 
     moves.foreach(engine.processUserInput)
@@ -93,7 +111,7 @@ class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
   // ── Check detection ────────────────────────────────────────────
 
   test("check detected after move puts king in check"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -108,7 +126,7 @@ class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
     observer.hasEvent[CheckDetectedEvent] shouldBe true
 
   test("check by knight"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -122,7 +140,7 @@ class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
   // ── Fifty-move rule ────────────────────────────────────────────
 
   test("fifty-move rule triggers when half-move clock reaches 100"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -155,7 +173,7 @@ class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
   // ── Draw claim ────────────────────────────────────────────────
 
   test("draw can be claimed when fifty-move rule is available"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -167,7 +185,7 @@ class GameEngineOutcomesTest extends AnyFunSuite with Matchers:
     observer.hasEvent[DrawClaimedEvent] shouldBe true
 
   test("draw cannot be claimed when not available"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 

modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala

@@ -24,54 +24,54 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
 
   test("processUserInput fires PromotionRequiredEvent when pawn reaches back rank") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = engineWith(promotionBoard)
-    val events = captureEvents(engine)
+    val engine         = engineWith(promotionBoard)
+    val events         = captureEvents(engine)
 
     engine.processUserInput("e7e8")
 
-    events.exists(_.isInstanceOf[PromotionRequiredEvent]) should be (true)
-    events.collect { case e: PromotionRequiredEvent => e }.head.from should be (sq(File.E, Rank.R7))
+    events.exists(_.isInstanceOf[PromotionRequiredEvent]) should be(true)
+    events.collect { case e: PromotionRequiredEvent => e }.head.from should be(sq(File.E, Rank.R7))
   }
 
   test("isPendingPromotion is true after PromotionRequired input") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = engineWith(promotionBoard)
+    val engine         = engineWith(promotionBoard)
     captureEvents(engine)
 
     engine.processUserInput("e7e8")
 
-    engine.isPendingPromotion should be (true)
+    engine.isPendingPromotion should be(true)
   }
 
   test("isPendingPromotion is false before any promotion input") {
     val engine = new GameEngine()
-    engine.isPendingPromotion should be (false)
+    engine.isPendingPromotion should be(false)
   }
 
   test("completePromotion fires MoveExecutedEvent with promoted piece") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = engineWith(promotionBoard)
-    val events = captureEvents(engine)
+    val engine         = engineWith(promotionBoard)
+    val events         = captureEvents(engine)
 
     engine.processUserInput("e7e8")
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-    engine.board.pieceAt(sq(File.E, Rank.R7)) should be (None)
+    engine.isPendingPromotion should be(false)
+    engine.board.pieceAt(sq(File.E, Rank.R8)) should be(Some(Piece(Color.White, PieceType.Queen)))
+    engine.board.pieceAt(sq(File.E, Rank.R7)) should be(None)
     engine.context.moves.last.moveType shouldBe MoveType.Promotion(PromotionPiece.Queen)
-    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be (true)
+    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be(true)
   }
 
   test("completePromotion with rook underpromotion") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = engineWith(promotionBoard)
+    val engine         = engineWith(promotionBoard)
     captureEvents(engine)
 
     engine.processUserInput("e7e8")
     engine.completePromotion(PromotionPiece.Rook)
 
-    engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Rook)))
+    engine.board.pieceAt(sq(File.E, Rank.R8)) should be(Some(Piece(Color.White, PieceType.Rook)))
   }
 
   test("completePromotion with no pending promotion fires InvalidMoveEvent") {
@@ -80,71 +80,71 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
 
     engine.completePromotion(PromotionPiece.Queen)
 
-    events.exists(_.isInstanceOf[InvalidMoveEvent]) should be (true)
-    engine.isPendingPromotion should be (false)
+    events.exists(_.isInstanceOf[InvalidMoveEvent]) should be(true)
+    engine.isPendingPromotion should be(false)
   }
 
   test("completePromotion fires CheckDetectedEvent when promotion gives check") {
     val promotionBoard = FenParser.parseBoard("3k4/4P3/8/8/8/8/8/8").get
-    val engine = engineWith(promotionBoard)
-    val events = captureEvents(engine)
+    val engine         = engineWith(promotionBoard)
+    val events         = captureEvents(engine)
 
     engine.processUserInput("e7e8")
     engine.completePromotion(PromotionPiece.Queen)
 
-    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (true)
+    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be(true)
   }
 
   test("completePromotion results in Moved when promotion doesn't give check") {
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/k7/8").get
+    val board  = FenParser.parseBoard("8/4P3/8/8/8/8/k7/8").get
     val engine = engineWith(board)
     val events = captureEvents(engine)
 
     engine.processUserInput("e7e8")
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
+    engine.isPendingPromotion should be(false)
+    engine.board.pieceAt(sq(File.E, Rank.R8)) should be(Some(Piece(Color.White, PieceType.Queen)))
     events.filter(_.isInstanceOf[MoveExecutedEvent]) should not be empty
-    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (false)
+    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be(false)
   }
 
   test("completePromotion results in Checkmate when promotion delivers checkmate") {
-    val board = FenParser.parseBoard("k7/7P/1K6/8/8/8/8/8").get
+    val board  = FenParser.parseBoard("k7/7P/1K6/8/8/8/8/8").get
     val engine = engineWith(board)
     val events = captureEvents(engine)
 
     engine.processUserInput("h7h8")
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[CheckmateEvent]) should be (true)
+    engine.isPendingPromotion should be(false)
+    events.exists(_.isInstanceOf[CheckmateEvent]) should be(true)
   }
 
   test("completePromotion results in Stalemate when promotion creates stalemate") {
-    val board = FenParser.parseBoard("k7/1PB5/1K6/8/8/8/8/8").get
+    val board  = FenParser.parseBoard("k7/1PB5/1K6/8/8/8/8/8").get
     val engine = engineWith(board)
     val events = captureEvents(engine)
 
     engine.processUserInput("b7b8")
     engine.completePromotion(PromotionPiece.Knight)
 
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[StalemateEvent]) should be (true)
+    engine.isPendingPromotion should be(false)
+    events.exists(_.isInstanceOf[StalemateEvent]) should be(true)
   }
 
   test("completePromotion with black pawn promotion results in Moved") {
-    val board = FenParser.parseBoard("k7/8/8/8/8/7K/4p3/8").get
+    val board  = FenParser.parseBoard("k7/8/8/8/8/7K/4p3/8").get
     val engine = engineWith(board, Color.Black)
     val events = captureEvents(engine)
 
     engine.processUserInput("e2e1")
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    engine.board.pieceAt(sq(File.E, Rank.R1)) should be (Some(Piece(Color.Black, PieceType.Queen)))
+    engine.isPendingPromotion should be(false)
+    engine.board.pieceAt(sq(File.E, Rank.R1)) should be(Some(Piece(Color.Black, PieceType.Queen)))
     events.filter(_.isInstanceOf[MoveExecutedEvent]) should not be empty
-    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (false)
+    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be(false)
   }
 
   test("completePromotion fires InvalidMoveEvent when legalMoves returns only Normal moves to back rank") {
@@ -177,21 +177,21 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
         DefaultRules.applyMove(context)(move)
 
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val initialCtx = GameContext.initial.withBoard(promotionBoard).withTurn(Color.White)
-    val engine = new GameEngine(initialCtx, delegatingRuleSet)
-    val events = captureEvents(engine)
+    val initialCtx     = GameContext.initial.withBoard(promotionBoard).withTurn(Color.White)
+    val engine         = new GameEngine(initialCtx, delegatingRuleSet)
+    val events         = captureEvents(engine)
 
     // isPromotionMove will fire because pawn is on rank 7 heading to rank 8,
     // and legalMoves returns Normal candidates (still non-empty) — sets pendingPromotion
     engine.processUserInput("e7e8")
-    engine.isPendingPromotion should be (true)
+    engine.isPendingPromotion should be(true)
 
     // completePromotion looks for Move(e7, e8, Promotion(Queen)) in legalMoves,
     // but only Normal moves exist → fires InvalidMoveEvent
     engine.completePromotion(PromotionPiece.Queen)
 
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[InvalidMoveEvent]) should be (true)
+    engine.isPendingPromotion should be(false)
+    events.exists(_.isInstanceOf[InvalidMoveEvent]) should be(true)
     val invalidEvt = events.collect { case e: InvalidMoveEvent => e }.last
-    invalidEvt.reason should include ("Error completing promotion")
+    invalidEvt.reason should include("Error completing promotion")
   }

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineScenarioTest.scala

@@ -1,6 +1,6 @@
 package de.nowchess.chess.engine
 
-import de.nowchess.api.board.{Color, File, Rank, Square, Piece}
+import de.nowchess.api.board.{Color, File, Piece, Rank, Square}
 import de.nowchess.api.game.GameContext
 import de.nowchess.chess.observer.*
 import de.nowchess.io.fen.FenParser
@@ -13,7 +13,7 @@ class GameEngineScenarioTest extends AnyFunSuite with Matchers:
   // ── Observer wiring ────────────────────────────────────────────
 
   test("observer subscribe and unsubscribe behavior"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
     engine.processUserInput("e2e4")
@@ -56,28 +56,28 @@ class GameEngineScenarioTest extends AnyFunSuite with Matchers:
   // ── Invalid moves (minimal) ────────────────────────────────────
 
   test("invalid move forms trigger InvalidMoveEvent and keep turn where relevant"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
     engine.processUserInput("h3h4")
 
     observer.hasEvent[InvalidMoveEvent] shouldBe true
-    engine.turn shouldBe Color.White  // turn unchanged
+    engine.turn shouldBe Color.White // turn unchanged
 
-    engine.processUserInput("e7e5")  // try to move black pawn on white's turn
+    engine.processUserInput("e7e5") // try to move black pawn on white's turn
 
     observer.hasEvent[InvalidMoveEvent] shouldBe true
 
     engine.processUserInput("e2e4")
-    engine.processUserInput("e5e4")  // pawn backward
+    engine.processUserInput("e5e4") // pawn backward
 
     observer.hasEvent[InvalidMoveEvent] shouldBe true
 
   // ── Undo/Redo ────────────────────────────────────────────────
 
   test("undo redo success and empty-history failures"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -103,7 +103,7 @@ class GameEngineScenarioTest extends AnyFunSuite with Matchers:
   // ── Fifty-move rule ────────────────────────────────────────────
 
   test("fifty-move event and draw claim success/failure"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineSpecialMovesTest.scala

@@ -11,7 +11,7 @@ class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
   // ── Castling ────────────────────────────────────────────────────
 
   test("kingside castling executes successfully"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -25,7 +25,7 @@ class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
     engine.turn shouldBe Color.Black
 
   test("queenside castling executes successfully"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -39,7 +39,7 @@ class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
     engine.turn shouldBe Color.Black
 
   test("undo castling emits PGN notation"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -57,7 +57,7 @@ class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
   // ── En passant ──────────────────────────────────────────────────
 
   test("en passant capture executes successfully"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -69,10 +69,10 @@ class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
 
     observer.hasEvent[MoveExecutedEvent] shouldBe true
     val moveEvt = observer.getEvent[MoveExecutedEvent]
-    moveEvt.get.capturedPiece shouldBe defined  // pawn was captured
+    moveEvt.get.capturedPiece shouldBe defined // pawn was captured
 
   test("undo en passant emits file-x-destination notation"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -90,7 +90,7 @@ class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
   // ── Pawn promotion ─────────────────────────────────────────────
 
   test("pawn reaching back rank requires promotion"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -143,7 +143,7 @@ class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
     engine.turn shouldBe Color.Black
 
   test("promotion to Queen with discovered check emits CheckDetectedEvent"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -157,7 +157,7 @@ class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
     observer.hasEvent[CheckDetectedEvent] shouldBe true
 
   test("promotion to Queen with checkmate emits CheckmateEvent"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)
 
@@ -171,7 +171,7 @@ class GameEngineSpecialMovesTest extends AnyFunSuite with Matchers:
     observer.hasEvent[CheckmateEvent] shouldBe true
 
   test("undo promotion emits notation with piece suffix"):
-    val engine = EngineTestHelpers.makeEngine()
+    val engine   = EngineTestHelpers.makeEngine()
     val observer = new EngineTestHelpers.MockObserver()
     engine.subscribe(observer)