You could pass the list as a string directly into the CSVParser instead of creating a writer.

CSVRecord csvr = CSVParser.parse(
values.stream().collect(Collectors.joining(","))
,csvFormat.withHeader(header.toArray(new String[header.size()])))
.getRecords().get(0);

I think Super CSV can help you, detail you can check this doc. Super CSV

private static void readWithCsvBeanReader() throws Exception {
        
        ICsvBeanReader beanReader = null;
        try {
                beanReader = new CsvBeanReader(new FileReader(CSV_FILENAME), CsvPreference.STANDARD_PREFERENCE);
                
                // the header elements are used to map the values to the bean (names must match)
                final String[] header = beanReader.getHeader(true);
                final CellProcessor[] processors = getProcessors();
                
                CustomerBean customer;
                while( (customer = beanReader.read(CustomerBean.class, header, processors)) != null ) {
                        System.out.println(String.format("lineNo=%s, rowNo=%s, customer=%s", beanReader.getLineNumber(),
                                beanReader.getRowNumber(), customer));
                }
                
        }
        finally {
                if( beanReader != null ) {
                        beanReader.close();
                }
        }
}

You can use Powermock. More info: https://github.com/powermock/powermock/wiki/mockfinal

example:

import org.apache.commons.csv.CSVRecord;
import static org.junit.Assert.assertEquals;
import org.junit.Test;
import org.junit.runner.RunWith;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest({CSVRecord.class}) // needed to mock final classes and static methods
public class YourTestClass {
    @Test
    public void testCheckValidNum_null() {
        String columnName = "colName";
        CSVRecord record = mock(CSVRecord.class);
        String contentsOfCol = "hello";
        String result;

        when(record.get(columnName)).thenReturn(contentsOfCol);

        result = record.get(columnName);

        assertEquals(contentsOfCol, result);
    }
}

Here are my maven includes (there are newer versions of libraries, this is just what I'm using):

<dependency>
    <groupId>org.powermock</groupId>
    <artifactId>powermock-module-junit4</artifactId>
    <version>1.7.4</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.powermock</groupId>
    <artifactId>powermock-api-mockito</artifactId>
    <version>1.7.4</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-all</artifactId>
    <version>1.8.5</version>
    <scope>test</scope>
</dependency>

You can simply iterate over the resulting records and access the i-th item of a record via record.get(i), e.g.

    Reader in = new StringReader(
            "DAR_123451                  ,\"XXXXX Hello World Hello World XXX \"\n" +
            "DAR_123452                  ,\"XXXXX Hello World Hello World XXX \"");
    Iterable<CSVRecord> records = CSVFormat.DEFAULT.parse(in);
    for (CSVRecord record : records) {
        for (int i = 0; i < record.size(); i++) {
            System.out.println("At " + i + ": " + record.get(i));
        }
    }