Add unit tests for #106

Author: cowtowncoder

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

@@ -2,19 +2,21 @@
 
 import java.io.ByteArrayOutputStream;
 import java.io.StringWriter;
+import java.util.Arrays;
+import java.util.List;
 
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.dataformat.csv.*;
 
 // for [dataformat-csv#69], other null value serialization
 public class NullWritingTest extends ModuleTestBase
 {
-    private final CsvMapper csv = new CsvMapper();
-    
     public static class Nullable {
         public String a, b, c, d;
     }
-     
+
+    private final CsvMapper csv = new CsvMapper();
+
     public void testObjectWithNullMembersToString() throws Exception {
         CsvSchema schema = csv.schemaFor(Nullable.class).withUseHeader(true);
         ObjectWriter writer = csv.writer(schema);
@@ -78,4 +80,44 @@ public void testCustomNullValue() throws Exception
         // MUST use doubling for quotes!
         assertEquals("id,n/a\n", result);
     }
+
+    public void testNullFieldsOfListsContainedByMainLevelListIssue106() throws Exception
+    {
+        CsvMapper mapper = mapperForCsv();
+        CsvSchema schema = CsvSchema.builder().build();
+
+        List<String> row1 = Arrays.asList("d0", null, "d2");
+        List<String> row2 = Arrays.asList(null, "d1", "d2");
+        List<String> row3 = Arrays.asList("d0", "d1", null);
+
+        List<List<String>> dataList = Arrays.asList(row1, row2, row3);
+
+        String result = mapper.writer(schema).writeValueAsString(dataList);
+        assertEquals("d0,,d2\n,d1,d2\nd0,d1,\n", result);
+
+        schema = schema.withNullValue("n/a");
+        result = mapper.writer(schema).writeValueAsString(dataList);
+        assertEquals("d0,n/a,d2\nn/a,d1,d2\nd0,d1,n/a\n", result);
+    }
+
+    public void testNullElementsOfMainLevelListIssue106() throws Exception
+    {
+        CsvMapper mapper = mapperForCsv();
+        CsvSchema schema = CsvSchema.builder().build();
+
+        List<String> row1 = Arrays.asList("d0", null, "d2");
+        List<String> row2 = Arrays.asList(null, "d1", "d2");
+        List<String> row3 = Arrays.asList("d0", "d1", null);
+
+        // when serialized, the added root level nulls at index 1 and 3
+        // should be absent from the output
+       List<List<String>> dataList = Arrays.asList(row1, null, row2, null, row3);
+
+        String result = mapper.writer(schema).writeValueAsString(dataList);
+        assertEquals("d0,,d2\n,d1,d2\nd0,d1,\n", result);
+
+        schema = schema.withNullValue("n/a");
+        result = mapper.writer(schema).writeValueAsString(dataList);
+        assertEquals("d0,n/a,d2\nn/a,d1,d2\nd0,d1,n/a\n", result);
+    }
 }