Create test to describe the behavior of TreeReference.contextualize

Also, take the chance to fix the new ref creation to copy not only the context's multiplicity value, but its predicates too.

src/main/java/org/javarosa/core/model/instance/TreeReference.java

@@ -328,6 +328,7 @@ public TreeReference contextualize (TreeReference contextRef) {
                 //may have been done.
                 if(newRef.getPredicate(i) == null) {
                     newRef.setMultiplicity(i, contextRef.getMultiplicity(i));
+                    newRef.addPredicate(i, contextRef.getPredicate(i));
                 }
             } else {
                 break;

src/test/java/org/javarosa/core/model/instance/TreeReferenceContextualizeTest.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2019 Nafundi
+ *
+ * Licensed 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.
+ */
+
+package org.javarosa.core.model.instance;
+
+import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.nullValue;
+import static org.javarosa.core.model.instance.TestHelpers.buildRef;
+import static org.junit.Assert.assertThat;
+
+import java.util.Arrays;
+import java.util.Collection;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(Parameterized.class)
+public class TreeReferenceContextualizeTest {
+    @Parameterized.Parameter(value = 0)
+    public String testCase;
+
+    @Parameterized.Parameter(value = 1)
+    public TreeReference a;
+
+    @Parameterized.Parameter(value = 2)
+    public TreeReference b;
+
+    @Parameterized.Parameter(value = 3)
+    public TreeReference expectedResult;
+
+    @Parameterized.Parameters(name = "{0}")
+    public static Collection<Object[]> data() {
+        return Arrays.asList(new Object[][]{
+            // Self references
+            {"Relative context ref", buildRef("bar"), buildRef("foo"), null},
+            {"Non-matching absolute refs", buildRef("/foo"), buildRef("/bar"), buildRef("/foo")},
+            {"Contextualizing a ref with itself and multiplicity #1", buildRef("/foo"), buildRef("/foo[2]"), buildRef("/foo[2]")},
+            {"Contextualizing a ref with itself and multiplicity #2", buildRef("/foo[-1]"), buildRef("/foo[2]"), buildRef("/foo[-1]")},
+            {"Contextualizing a ref with itself and multiplicity #3", buildRef("/foo[0]"), buildRef("/foo[2]"), buildRef("/foo[0]")},
+            {"Contextualizing a ref with itself and multiplicity #4", buildRef("/foo[3]"), buildRef("/foo[2]"), buildRef("/foo[3]")},
+            {"Contextualizing a ref with itself and predicate #1", buildRef("/foo"), buildRef("/foo[position() = 3]"), buildRef("/foo[position() = 3]")},
+            {"Contextualizing a ref with itself and predicate #2", buildRef("/foo[position() = 2]"), buildRef("/foo[position() = 3]"), buildRef("/foo[position() = 2]")},
+            {"Wildcards #1", buildRef("bar"), buildRef("/foo/*"), buildRef("/foo/*/bar")},
+            {"Wildcards #2", buildRef("../baz"), buildRef("/foo/*/bar"), buildRef("/foo/*/baz")},
+            {"Wildcards #3", buildRef("*/baz"), buildRef("/foo/*/bar"), buildRef("/foo/*/bar/*/baz")},
+            {"Wildcards #4", buildRef("*/bar"), buildRef("/foo"), buildRef("/foo/*/bar")},
+        });
+    }
+
+
+    @Test
+    public void contextualize() {
+        assertThat(
+            a.contextualize(b),
+            expectedResult == null
+                ? nullValue()
+                : is(expectedResult)
+        );
+    }
+
+}