Create TestMixedCollections.java (#4149)

Author: pjfanning

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

@@ -0,0 +1,40 @@
+package com.fasterxml.jackson.databind.deser;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+// tests based on tests in vavr-jackson
+public class TestMixedCollections extends BaseMapTest {
+
+    public void testMapOfLists() throws IOException {
+        HashMap<Object, Object> src = new HashMap<>();
+        ArrayList<Integer> l1 = new ArrayList<>();
+        l1.add(1);
+        l1.add(2);
+        ArrayList<Integer> l2 = new ArrayList<>();
+        l2.add(3);
+        l2.add(4);
+        src.put("key1", l1);
+        src.put("key2", l2);
+        ObjectMapper mapper = newJsonMapper();
+        String json = mapper.writer().writeValueAsString(src);
+        assertEquals(src, mapper.readValue(json, new TypeReference<Map<?, List<?>>>() {}));
+    }
+
+    public void testMapOfMaps() throws IOException {
+        HashMap<Object, Object> src = new HashMap<>();
+        HashMap<Object, Object> innerMap = new HashMap<>();
+        innerMap.put("X", "Y");
+        src.put("1", innerMap);
+        ObjectMapper mapper = newJsonMapper();
+        String json = mapper.writer().writeValueAsString(src);
+        assertEquals(src, mapper.readValue(json, new TypeReference<Map<?, Map<?, ?>>>() {}));
+    }
+}