Fix loop's statements copy

src/main/java/org/mozilla/zest/core/v1/ZestLoop.java

@@ -361,13 +361,15 @@ public void onControlNext(){
 	 * @return the list of copied statements
 	 */
 	public List<ZestStatement> copyStatements() {
-		if (this.getStatements() != null) {
-			List<ZestStatement> statements = new LinkedList<>();
-			for (ZestStatement stmt : this.getStatements()) {
-				statements.add(stmt.deepCopy());
-			}
+		List<ZestStatement> copiedStatements = new LinkedList<>();
+		if (this.getStatements() == null) {
+			return copiedStatements;
+		}
+
+		for (ZestStatement stmt : getStatements()) {
+			copiedStatements.add(stmt.deepCopy());
 		}
-		return statements;
+		return copiedStatements;
 	}
 
 	/**

src/test/java/org/mozilla/zest/test/v1/ZestLoopUnitTest.java

@@ -0,0 +1,73 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+package org.mozilla.zest.test.v1;
+
+import static org.junit.Assert.assertTrue;
+
+import java.util.List;
+
+import org.junit.Test;
+import org.mozilla.zest.core.v1.ZestComment;
+import org.mozilla.zest.core.v1.ZestLoop;
+import org.mozilla.zest.core.v1.ZestLoopTokenSet;
+import org.mozilla.zest.core.v1.ZestStatement;
+
+/**
+ * Unit test for {@link ZestLoop}.
+ */
+public class ZestLoopUnitTest {
+
+    @Test
+    public void shouldReturnEmptyListIfNoStatementsWhenCopyingStatements() throws Exception {
+        // Given
+        ZestLoop<String> loop = new ZestLoopTest();
+        // When
+        List<ZestStatement> copiedStatements = loop.copyStatements();
+        // Then
+        assertTrue(copiedStatements.isEmpty());
+    }
+
+    @Test
+    public void shouldReturnADifferentListAndStatementsWhenCopyingStatements() throws Exception {
+        // Given
+        ZestLoop<String> loop = new ZestLoopTest();
+        loop.addStatement(new ZestComment());
+        loop.addStatement(new ZestComment());
+        // When
+        List<ZestStatement> copiedStatements = loop.copyStatements();
+        // Then
+        assertTrue(copiedStatements != loop.getStatements());
+        assertTrue(copiedStatements.size() == loop.getStatements().size());
+        assertTrue(copiedStatements.get(0) != loop.getStatements().get(0));
+        assertTrue(copiedStatements.get(1) != loop.getStatements().get(1));
+    }
+
+    private static class ZestLoopTest extends ZestLoop<String> {
+
+        @Override
+        public ZestLoopTokenSet<String> getSet() {
+            return null;
+        }
+
+        @Override
+        public ZestLoop<String> deepCopy() {
+            return null;
+        }
+
+        @Override
+        public boolean isLastState() {
+            return false;
+        }
+
+        @Override
+        protected void increase() {
+        }
+
+        @Override
+        public void toLastState() {
+        }
+
+    }
+
+}