Minor test coverage improvement; ensure round-trippability of JDK singleton collections/maps

Author: cowtowncoder

src/test/java/com/fasterxml/jackson/databind/deser/TestCollectionDeserialization.java

@@ -37,6 +37,9 @@ public CustomList deserialize(JsonParser jp, DeserializationContext ctxt)
 
     static class XBean {
         public int x;
+
+        public XBean() { }
+        public XBean(int x) { this.x = x; }
     }
 
     // [Issue#199]
@@ -281,4 +284,22 @@ public void testWrapExceptions() throws Exception
             assertEquals("I want to catch this exception", exc.getMessage());
         }
     }
+
+    // And then a round-trip test for singleton collections
+    public void testSingletonCollections() throws Exception
+    {
+        final TypeReference<?> xbeanListType = new TypeReference<List<XBean>>() { };
+
+        String json = MAPPER.writeValueAsString(Collections.singleton(new XBean(3)));
+        Collection<XBean> result = MAPPER.readValue(json, xbeanListType);
+        assertNotNull(result);
+        assertEquals(1, result.size());
+        assertEquals(3, result.iterator().next().x);
+
+        json = MAPPER.writeValueAsString(Collections.singletonList(new XBean(28)));
+        result = MAPPER.readValue(json, xbeanListType);
+        assertNotNull(result);
+        assertEquals(1, result.size());
+        assertEquals(28, result.iterator().next().x);
+    }
 }

src/test/java/com/fasterxml/jackson/databind/deser/TestMapDeserialization.java

@@ -11,6 +11,7 @@
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.fasterxml.jackson.databind.deser.TestCollectionDeserialization.XBean;
 import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
 
 @SuppressWarnings("serial")
@@ -576,7 +577,21 @@ public void testReadProperties() throws Exception
         assertEquals("123", props.getProperty("b"));
         assertEquals("true", props.getProperty("c"));
     }
-    
+
+    // JDK singletonMap
+    public void testSingletonMapRoundtrip() throws Exception
+    {
+        final TypeReference<?> type = new TypeReference<Map<String,IntWrapper>>() { };
+
+        String json = MAPPER.writeValueAsString(Collections.singletonMap("value", new IntWrapper(5)));
+        Map<String,IntWrapper> result = MAPPER.readValue(json, type);
+        assertNotNull(result);
+        assertEquals(1, result.size());
+        IntWrapper w = result.get("value");
+        assertNotNull(w);
+        assertEquals(5, w.i);
+    }
+
     /*
     /**********************************************************
     /* Error tests