Add test case to reproduce multiplicity=1 simple type association issue

Co-authored-by: slachiewicz <[email protected]>

Author: Copilot

modello-plugins/modello-plugin-xpp3/src/test/java/org/codehaus/modello/generator/xml/xpp3/SimpleAssociationXpp3GeneratorTest.java

@@ -0,0 +1,46 @@
+package org.codehaus.modello.generator.xml.xpp3;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.util.Map;
+
+import org.codehaus.modello.AbstractModelloJavaGeneratorTest;
+import org.codehaus.modello.core.ModelloCore;
+import org.codehaus.modello.model.Model;
+
+public class SimpleAssociationXpp3GeneratorTest extends AbstractModelloJavaGeneratorTest {
+    public SimpleAssociationXpp3GeneratorTest() {
+        super("testSimpleAssociation");
+    }
+
+    public void testSimpleAssociation() throws Throwable {
+        ModelloCore modello = (ModelloCore) lookup(ModelloCore.ROLE);
+
+        Model model = modello.loadModel(getXmlResourceReader("/simple-association.mdo"));
+
+        Map<String, Object> parameters = getModelloParameters("1.0.0", 8);
+
+        modello.generate(model, "java", parameters);
+        modello.generate(model, "xpp3-reader", parameters);
+        modello.generate(model, "xpp3-writer", parameters);
+
+        compileGeneratedSources(8);
+    }
+}

modello-plugins/modello-plugin-xpp3/src/test/resources/simple-association.mdo

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<model xmlns="http://codehaus-plexus.github.io/MODELLO/1.4.0"
+       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xsi:schemaLocation="http://codehaus-plexus.github.io/MODELLO/1.4.0
+                           http://codehaus-plexus.github.io/modello/xsd/modello-1.4.0.xsd">
+  <id>test</id>
+  <name>SimpleAssociationTest</name>
+  <defaults>
+    <default>
+      <key>package</key>
+      <value>org.codehaus.modello.generator.xml.xpp3.test.simpleassociation</value>
+    </default>
+  </defaults>
+  <classes>
+    <class rootElement="true" xml.tagName="root">
+      <name>Root</name>
+      <version>1.0.0+</version>
+      <fields>
+        <field>
+          <name>stringField</name>
+          <version>1.0.0+</version>
+          <association>
+            <type>String</type>
+            <multiplicity>1</multiplicity>
+          </association>
+        </field>
+      </fields>
+    </class>
+  </classes>
+</model>