Unit testing a method that takes a ResultSet as parameter

Laurens :

How does one go about unit testing an object that can't be instantiated? Because currently I have a method that converts a ResultSet to an object but I'm unsure if this violates any programming principles.

public CItem convert(ResultSet rs) {
    CItem ci = new CItem ();

    try {
        ci.setHinumber(rs.getString("id"));
        ci.setHostname(rs.getString("sysname"));
        ci.setOs(rs.getString("zos"));
        ci.setTenant(rs.getString("customer_name"));
        //ci.setInstallation(rs.getField("installation_name"));
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return ci;
}

Do I need to look for a different way to approach this solely because it can't be unit tested? Or can I somehow fake a ResultSet object.

Any help would be appreciated.

Nicolas Filotto :

You could simply mock your ResultSet to provide a value for each field and check that the result contains what you expect.

For example with Mockito, your test would be something like this:

@RunWith(MockitoJUnitRunner.class)
public class SomeClassTest {

    @Mock
    private ResultSet resultSet;

    @Test
    public void testConvert() throws SQLException {
        // Define the behavior of the mock for each getString method's call
        Mockito.when(resultSet.getString("id")).thenReturn("myId");
        Mockito.when(resultSet.getString("sysname")).thenReturn("myHost");
        Mockito.when(resultSet.getString("zos")).thenReturn("myOS");
        Mockito.when(resultSet.getString("customer_name")).thenReturn("myCustomerName");

        // Launch the method against your mock
        SomeClass someClass = new SomeClass();
        CItem item = someClass.convert(resultSet);

        // Check the result
        Assert.assertNotNull(item);
        Assert.assertEquals("myId", item.getHinumber());
        Assert.assertEquals("myHost", item.getHostname());
        Assert.assertEquals("myOS", item.getOs());
        Assert.assertEquals("myCustomerName", item.getTenant());
    }
}