Add a simple test for JsonMapper.rebuild()

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/databind/json/JsonMapper.java

@@ -118,7 +118,7 @@ public static Builder builder(JsonFactory streamFactory) {
         return new Builder(new JsonMapper(streamFactory));
     }
 
-    public JsonMapper.Builder  rebuild() {
+    public JsonMapper.Builder rebuild() {
         // 09-Dec-2018, tatu: Not as good as what 3.0 has wrt immutability, but best approximation
         //     we have for 2.x
         return new Builder(this.copy());

src/test/java/com/fasterxml/jackson/databind/ObjectMapperTest.java

@@ -12,7 +12,7 @@
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.core.json.JsonWriteFeature;
 import com.fasterxml.jackson.core.util.MinimalPrettyPrinter;
-
+import com.fasterxml.jackson.databind.cfg.EnumFeature;
 import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;
 import com.fasterxml.jackson.databind.introspect.VisibilityChecker;
 import com.fasterxml.jackson.databind.json.JsonMapper;
@@ -267,6 +267,27 @@ public void testAnnotationIntrospectorCopying()
                 m2.getSerializationConfig().getAnnotationIntrospector().getClass());
     }
 
+    /*
+    /**********************************************************
+    /* Test methods, JsonMapper.rebuild()
+    /**********************************************************
+     */
+
+    @Test
+    public void jsonMapperRebuildTest()
+    {
+        JsonMapper m = JsonMapper.builder().build();
+        JsonMapper m2 = m.copy();
+        assertNotSame(m, m2);
+
+        JsonMapper m3 = m2.rebuild()
+                .propertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE)
+                .enable(MapperFeature.ACCEPT_CASE_INSENSITIVE_ENUMS)
+                .enable(EnumFeature.WRITE_ENUMS_TO_LOWERCASE)
+                .build();
+        assertNotSame(m2, m3);
+    }
+
     /*
     /**********************************************************
     /* Test methods, other