Extensive tests for faroShuffle added

tests/edu/caltech/cs0/war/DeckTests.java

@@ -9,10 +9,7 @@ import org.junit.jupiter.params.provider.CsvSource;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.Random;
+import java.util.*;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -93,6 +90,10 @@ public class DeckTests {
       return inner;
     }
 
+    private static List<Card> cloneList(List<Card> list) {
+      return (ArrayList<Card>) ((ArrayList<Card>) list).clone();
+    }
+
     @Test
     @DisplayName("hasNoCards returns true on an empty deck")
     public void testHasNoCardsEmpty() {
@@ -174,7 +175,7 @@ public class DeckTests {
       List<Card> ref = new ArrayList<>();
       for (int i = 1; i < 10; i++) {
         final int drawCount = i; // should throw an exception for numCards drawn (deck has numCards - 1 cards)
-        final List<Card> inp = (ArrayList<Card>) ((ArrayList<Card>) ref).clone();
+        final List<Card> inp = cloneList(ref);
         assertThrowsExactly(EmptyDeckException.class, () -> newDeck(inp).draw(drawCount));
         ref.add(new Card(null, null));
       }
@@ -213,25 +214,83 @@ public class DeckTests {
       assertEquals(List.of(), getList(deck));
     }
 
-    //TODO: write more tests for faroShuffle?
-    //public void faroShuffle() {
+    @Test
+    @DisplayName("faroShuffle of decks with 0-3 cards work as expected (no effect on 0-2, swap last 2 cards for 3)")
+    public void testFaroShuffleSmall() {
+      List<Card> ref = new ArrayList<>();
+      Deck deck = newDeck(cloneList(ref));
+      for (int i = 0; i < 2; i++) {
+        deck.faroShuffle();
+        assertEquals(ref, getList(deck));
+      }
+      ref.add(new Card(Rank.ACE, null));
+      deck = newDeck(cloneList(ref));
+      for (int i = 0; i < 2; i++) {
+        deck.faroShuffle();
+        assertEquals(ref, getList(deck));
+      }
+      ref.add(new Card(Rank.TWO, null));
+      deck = newDeck(cloneList(ref));
+      for (int i = 0; i < 5; i++) {
+        deck.faroShuffle();
+        assertEquals(ref, getList(deck));
+      }
+      ref.add(new Card(Rank.THREE, null));
+      deck = newDeck(cloneList(ref));
+      List<Card> swapped = List.of(new Card(Rank.ACE, null), new Card(Rank.THREE, null), new Card(Rank.TWO, null));
+      for (int i = 0; i < 10; i++) {
+        deck.faroShuffle();
+        if (i % 2 == 0) assertEquals(swapped, getList(deck));
+        else assertEquals(ref, getList(deck));
+      }
+    }
+
+    public class CardIterator implements Iterator<Card> {
+      private Rank[] ranks = Rank.values();
+      private Suit[] suits = Suit.values();
+      private int rankIdx = 0;
+      private int suitIdx = 0;
+      @Override
+      public boolean hasNext() {
+        return rankIdx < ranks.length && suitIdx < suits.length;
+      }
+      @Override
+      public Card next() {
+        Card card = new Card(ranks[rankIdx], suits[suitIdx]);
+        suitIdx++;
+        if (suitIdx >= suits.length) {
+          suitIdx = 0;
+          rankIdx++;
+        }
+        return card;
+      }
+    }
 
     @Test
-    public void testPerfectFaroShuffle() {
-      Deck d = new Deck();
-      Field dl = Reflection.getFieldByType(Deck.class, List.class);
-      assert dl != null;
-      List<Card> curr = Reflection.getFieldValue(Deck.class, dl.getName(), d);
-      assert curr != null;
-      List<Card> initCopy = curr.stream().toList();
-      for (int i = 0; i < 7; i++) {
-       d.faroShuffle();
-       curr = Reflection.getFieldValue(Deck.class, dl.getName(), d);
-       assertNotEquals(initCopy, curr);
+    @DisplayName("faroShuffle of decks with 1-52 cards works as expected via perfect shuffle properties")
+    public void testFaroShuffleBig() {
+      Iterator<Card> cardGen = new CardIterator();
+      List<Card> ref = new ArrayList<>();
+      for (int i = 0; i < 52; i++) {
+        ref.add(cardGen.next());
+        Deck deck = newDeck(cloneList(ref));
+        int size = ref.size();
+        int modBy = size;
+        if (size % 2 == 0) modBy -= 1;
+        long pow = 1;
+        boolean firstMatch = 1 % modBy != 1;
+        for (int shuffles = 1; shuffles < 63; shuffles++) {
+          pow *= 2;
+          if (pow % modBy == 1) {
+            for (int j = 0; j < shuffles; j++) {
+              deck.faroShuffle();
+              if (firstMatch) assertNotEquals(ref, getList(deck));
+            }
+            firstMatch = false;
+            assertEquals(ref, getList(deck));
+          }
+        }
       }
-      d.faroShuffle();
-      curr = Reflection.getFieldValue(Deck.class, dl.getName(), d);
-      assertEquals(initCopy, curr);
-     }
+    }
   }
 }