Fix divergent changes removal, improve unit test

core/src/main/java/dev/kske/undoredo/core/UnlimitedChangeManager.java

@@ -27,8 +27,7 @@ public final class UnlimitedChangeManager<C extends Change> implements ChangeMan
 			change.apply();
 
 			// Remove divergent changes
-			for (int i = index + 1; i < changes.size(); ++i)
-				changes.remove(i);
+			changes.subList(index + 1, changes.size()).clear();
 
 			changes.add(change);
 			++index;

core/src/test/java/dev/kske/undoredo/core/ChangeManagerTest.java

@@ -14,11 +14,22 @@ class ChangeManagerTest {
 	IntWrapper					wrapper;
 	IntChange					change;
 
+	/**
+	 * Generates an int change with the given value.
+	 *
+	 * @param value the value of the change
+	 * @return the created change
+	 * @since 0.0.1
+	 */
+	IntChange change(int value) {
+		return new IntChange(wrapper, value);
+	}
+
 	@BeforeEach
 	void prepareChangeManager() {
 		manager	= new UnlimitedChangeManager<>();
 		wrapper	= new IntWrapper();
-		change	= new IntChange(wrapper, 1);
+		change	= change(1);
 	}
 
 	/**
@@ -43,7 +54,7 @@ class ChangeManagerTest {
 	@Order(15)
 	void testDiscardIdentity() {
 		manager.addChange(change);
-		assertFalse(manager.addChange(new IntChange(wrapper, 0)));
+		assertFalse(manager.addChange(change(0)));
 		assertSame(1, wrapper.value);
 	}
 
@@ -122,10 +133,13 @@ class ChangeManagerTest {
 	@Order(55)
 	void testDiscardDivergentHistory() {
 		manager.addChange(change);
+		manager.addChange(change(2));
 		manager.undo();
-		assertTrue(manager.addChange(new IntChange(wrapper, 2)));
+		manager.undo();
+		assertTrue(manager.addChange(change(3)));
 		assertFalse(manager.isRedoAvailable());
-		assertSame(2, wrapper.value);
+		assertSame(3, wrapper.value);
+		assertSame(1, manager.getChanges().size());
 	}
 
 	/**

core/src/test/java/dev/kske/undoredo/core/IntChange.java

@@ -1,5 +1,7 @@
 package dev.kske.undoredo.core;
 
+import java.util.Objects;
+
 /**
  * @author Kai S. K. Engelbart
  * @since 0.0.1
@@ -28,4 +30,24 @@ class IntChange implements Change {
 	public boolean isIdentity() {
 		return value == 0;
 	}
+
+	@Override
+	public String toString() {
+		return String.valueOf(value);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(value, wrapper);
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (!(obj instanceof IntChange))
+			return false;
+		IntChange other = (IntChange) obj;
+		return value == other.value && Objects.equals(wrapper, other.wrapper);
+	}
 }

core/src/test/java/dev/kske/undoredo/core/IntWrapper.java

@@ -1,5 +1,7 @@
 package dev.kske.undoredo.core;
 
+import java.util.Objects;
+
 /**
  * @author Kai S. K. Engelbart
  * @since 0.0.1
@@ -7,4 +9,24 @@ package dev.kske.undoredo.core;
 class IntWrapper {
 
 	int value;
+
+	@Override
+	public String toString() {
+		return String.valueOf(value);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(value);
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (!(obj instanceof IntWrapper))
+			return false;
+		IntWrapper other = (IntWrapper) obj;
+		return value == other.value;
+	}
 }