adds readName test about single discriminator serialization

bson/src/test/unit/org/bson/codecs/pojo/PojoCodecDiscriminatorTest.java

@@ -18,6 +18,7 @@
 
 import org.bson.codecs.pojo.entities.DiscriminatorModel;
 import org.bson.codecs.pojo.entities.DiscriminatorWithGetterModel;
+import org.bson.codecs.pojo.entities.DiscriminatorWithProperty;
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
@@ -26,7 +27,7 @@ public final class PojoCodecDiscriminatorTest extends PojoTestCase {
 
     @Test
     public void testDiscriminatorEncodedOnceWhenItIsAlsoAGetter() {
-        byte[] encodedDiscriminatorWithoutGetter = encode(
+        byte[] encodedDiscriminatorModel = encode(
                 getCodec(DiscriminatorModel.class),
                 new DiscriminatorModel(),
                 false
@@ -36,7 +37,7 @@ public void testDiscriminatorEncodedOnceWhenItIsAlsoAGetter() {
                 new DiscriminatorWithGetterModel(),
                 false
         ).toByteArray();
-        assertArrayEquals(encodedDiscriminatorWithoutGetter, encodedDiscriminatorWithGetter);
+        assertArrayEquals(encodedDiscriminatorModel, encodedDiscriminatorWithGetter);
     }
 
     @Test
@@ -46,4 +47,27 @@ public void testDiscriminatorRoundTripWhenItIsAlsoAGetter() {
                 "{discriminatorKey:'discriminatorValue'}"
         );
     }
+
+    @Test
+    public void testDiscriminatorEncodedOnceWhenItIsAlsoAProperty() {
+        byte[] encodedDiscriminatorModel = encode(
+                getCodec(DiscriminatorModel.class),
+                new DiscriminatorModel(),
+                false
+        ).toByteArray();
+        byte[] encodedDiscriminatorWithProperty = encode(
+                getCodec(DiscriminatorWithProperty.class),
+                new DiscriminatorWithProperty(),
+                false
+        ).toByteArray();
+        assertArrayEquals(encodedDiscriminatorModel, encodedDiscriminatorWithProperty);
+    }
+
+    @Test
+    public void testDiscriminatorRoundTripWhenItIsAlsoAProperty() {
+        roundTrip(
+                new DiscriminatorWithProperty(),
+                "{discriminatorKey:'discriminatorValue'}"
+        );
+    }
 }

bson/src/test/unit/org/bson/codecs/pojo/entities/DiscriminatorWithProperty.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * 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.bson.codecs.pojo.entities;
+
+import org.bson.codecs.pojo.annotations.BsonDiscriminator;
+import org.bson.codecs.pojo.annotations.BsonProperty;
+
+import java.util.Objects;
+
+@BsonDiscriminator(key = "discriminatorKey", value = "discriminatorValue")
+public class DiscriminatorWithProperty {
+
+    public DiscriminatorWithProperty() {
+    }
+
+    @BsonProperty("discriminatorKey")
+    public String getDiscriminator() {
+        return "discriminatorValue";
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (o == null || getClass() != o.getClass()) return false;
+        final DiscriminatorWithProperty that = (DiscriminatorWithProperty) o;
+        return Objects.equals(getDiscriminator(), that.getDiscriminator());
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(getDiscriminator());
+    }
+
+    @Override
+    public String toString() {
+        return "DiscriminatorWithProperty{}";
+    }
+}