Add a test for #125

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/dataformat/csv/CsvGenerator.java

@@ -540,7 +540,7 @@ public final void writeEndObject() throws IOException
         // not 100% fool-proof, but chances are row should be done now
         finishRow();
     }
-    
+
     /*
     /**********************************************************
     /* Output method implementations, textual

src/test/java/com/fasterxml/jackson/dataformat/csv/ser/UnwrappedWriteTest.java

@@ -0,0 +1,36 @@
+package com.fasterxml.jackson.dataformat.csv.ser;
+
+import com.fasterxml.jackson.annotation.*;
+
+import com.fasterxml.jackson.dataformat.csv.*;
+
+public class UnwrappedWriteTest extends ModuleTestBase
+{
+    @JsonPropertyOrder({ "f1", "f2", "f3" })
+    static class Inner {
+        public String f1;
+        public String f2;
+        public String f3;
+    }
+
+    @JsonPropertyOrder({ "a", "inner" })
+    static class Outer {
+        public String a;
+
+        @JsonUnwrapped
+        public Inner inner = new Inner();
+    }
+
+    // for [dataformat-csv#125]
+    public void testWriteUnwrapped() throws Exception
+    {
+        CsvMapper mapper = mapperForCsv();
+
+        // Set null value to 'null'
+        final CsvSchema schema = mapper.schemaFor(Outer.class).withNullValue("null");
+
+        // Create an object. All the fields are NULLs
+        String csv = mapper.writer(schema).writeValueAsString(new Outer());
+        assertEquals("null,null,null,null", csv.trim());
+    }
+}