Improve test suite focusing on the DAG's behavior

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)
+        );
+    }
+
+}