Added unit test covering case in PR #249.

Author: PrimosK

src/test/java/com/microsoft/graph/models/MessageStub.java

@@ -0,0 +1,20 @@
+package com.microsoft.graph.models;
+
+import com.google.gson.annotations.Expose;
+import com.google.gson.annotations.SerializedName;
+
+/**
+ * This class shouldn't be moved as it's location in this
+ * particular package is tightly coupled with the logic present at:
+ * com/microsoft/graph/serializer/DerivedClassIdentifier.java:38
+ */
+public class MessageStub extends TestIJsonBackedObject {
+
+    @SerializedName("name")
+    @Expose()
+    public String name;
+
+    @SerializedName("reaction")
+    @Expose()
+    public ReactionStub reaction;
+}

src/test/java/com/microsoft/graph/models/MessagesCollectionResponseStub.java

@@ -0,0 +1,10 @@
+package com.microsoft.graph.models;
+
+import com.microsoft.graph.http.BaseCollectionResponse;
+
+public class MessagesCollectionResponseStub extends BaseCollectionResponse<MessageStub> {
+
+    public MessagesCollectionResponseStub() {
+    }
+
+}

src/test/java/com/microsoft/graph/models/ReactionStub.java

@@ -0,0 +1,21 @@
+package com.microsoft.graph.models;
+
+import com.google.gson.annotations.Expose;
+import com.google.gson.annotations.SerializedName;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * This class shouldn't be moved as it's location in this
+ * particular package is tightly coupled with the logic present at:
+ * com/microsoft/graph/serializer/DerivedClassIdentifier.java:38
+ */
+public class ReactionStub extends TestIJsonBackedObject {
+
+    /**
+     * the OData type of the object as returned by the service
+     */
+    @SerializedName("@odata.type")
+    @Expose
+    @Nullable
+    public String oDataType;
+}

src/test/java/com/microsoft/graph/models/SubReactionStub1.java

@@ -0,0 +1,10 @@
+package com.microsoft.graph.models;
+
+/**
+ * This class shouldn't be moved as it's location in this
+ * particular package is tightly coupled with the logic present at:
+ * com/microsoft/graph/serializer/DerivedClassIdentifier.java:38
+ */
+public class SubReactionStub1 extends ReactionStub {
+
+}

src/test/java/com/microsoft/graph/models/SubReactionStub2.java

@@ -0,0 +1,10 @@
+package com.microsoft.graph.models;
+
+/**
+ * This class shouldn't be moved as it's location in this
+ * particular package is tightly coupled with the logic present at:
+ * com/microsoft/graph/serializer/DerivedClassIdentifier.java:38
+ */
+public class SubReactionStub2 extends ReactionStub {
+
+}

src/test/java/com/microsoft/graph/models/TestIJsonBackedObject.java

@@ -0,0 +1,24 @@
+package com.microsoft.graph.models;
+
+import com.google.gson.JsonObject;
+import com.microsoft.graph.serializer.AdditionalDataManager;
+import com.microsoft.graph.serializer.IJsonBackedObject;
+import com.microsoft.graph.serializer.ISerializer;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import static org.mockito.Mockito.mock;
+
+public abstract class TestIJsonBackedObject implements IJsonBackedObject {
+
+    @Override
+    public void setRawObject(@NotNull ISerializer serializer, @NotNull JsonObject json) {
+        // Do nothing
+    }
+
+    @Nullable
+    @Override
+    public AdditionalDataManager additionalDataManager() {
+        return mock(AdditionalDataManager.class);
+    }
+}

src/test/java/com/microsoft/graph/serializer/FallbackTypeAdapterFactoryTest.java

@@ -0,0 +1,54 @@
+package com.microsoft.graph.serializer;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonObject;
+import com.google.gson.reflect.TypeToken;
+import com.microsoft.graph.http.BaseCollectionResponse;
+import com.microsoft.graph.logger.ILogger;
+import com.microsoft.graph.models.MessageStub;
+import com.microsoft.graph.models.MessagesCollectionResponseStub;
+import com.microsoft.graph.models.SubReactionStub1;
+import com.microsoft.graph.models.SubReactionStub2;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.junit.jupiter.api.Test;
+
+import java.lang.reflect.Type;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
+
+public class FallbackTypeAdapterFactoryTest {
+
+    /**
+     * This test covers the scenario of objects not being
+     * properly deserialized (@odata.type not taken into account):
+     * https://github.com/microsoftgraph/msgraph-sdk-java-core/pull/249
+     */
+    @Test
+    public void testDeserializationOfNestedODataTypeAnnotatedObjects() {
+        final ILogger logger = mock(ILogger.class);
+        final Gson gsonInstance = GsonFactory.getGsonInstance(logger);
+
+        final Type listType = new TypeToken<MessagesCollectionResponseStub>(){}.getType();
+        final String testJsonResponse =
+            "{\"value\": " +
+            "  [" +
+            "    {\"name\": \"parent1\",\"reaction\": {\"@odata.type\": \"#microsoft.graph.subReactionStub1\"}}," +
+            "    {\"name\": \"parent2\",\"reaction\": {\"@odata.type\": \"#microsoft.graph.subReactionStub2\"}}" +
+            "  ]" +
+            "}";
+
+        final BaseCollectionResponse<MessageStub> baseCollectionResponse = gsonInstance.fromJson(testJsonResponse, listType);
+
+        assertNotNull(baseCollectionResponse.value);
+
+        final MessageStub messageStub1 = baseCollectionResponse.value.get(0);
+        final MessageStub messageStub2 = baseCollectionResponse.value.get(1);
+
+        assertTrue(messageStub1.reaction instanceof SubReactionStub1);
+        assertTrue(messageStub2.reaction instanceof SubReactionStub2);
+    }
+
+}