PODAM (POjo DAta Mocker)

Writing unit tests, especially for data converters, requires creating a lot of POJOs and populate them to see that fields’ values are mapped correctly. In my previous experience, projects had simple POJOs and it was not a big deal to fill them with data manually, however, one of the last projects has complex model and creating test objects with all the relations became an issue. I started to finding for a solution that can create and populate objects for me and found a great tool called PODAM.

PODAM is abbreviation for POjo DAta Mocker and its API for creating beans is pretty simple. All you need to do is create PodamFactory instance and use its manufacturePojo method that instantiates object and fills its fields with random values:

PodamFactory factory = new PodamFactoryImpl();
Order order = factory.manufacturePojo(Order.class);

Sometimes you need to specify rules for field values. For example, ids of entities have String type and UUIDformat. For generated entities to pass validation logic smoothly it is necessary to generate valid ids. PODAM suggests two ways to deal with such issues:

The first one is to implement AttributeStrategy class and add @PodamStrategyValue annotation on required field. However, in my case this approach was undesirable, because I needed to test business entities and it is not a good idea to clutter them with annotation from test dependencies.

The second approach is to implement custom TypeManufacturer

public class CustomStringManufacturer extends StringTypeManufacturerImpl {

    private static final String FIELD_ID = "id";

    @Override
    public String getType(final DataProviderStrategy strategy, final AttributeMetadata attributeMetadata,
                    	  final Map<String, Type> genericTypesArgumentsMap) {
        if (FIELD_ID.equals(attributeMetadata.getAttributeName())) {
            return UUID.randomUUID().toString();
        }
        return super.getType(strategy, attributeMetadata, genericTypesArgumentsMap);
    };

}

and register it for using by PodamFactory

podamFactory.getStrategy().addOrReplaceTypeManufacturer(String.class, new CustomStringManufacturer());

I described only a subset of PODAM features. You can always visit their documentation for further info.

Another alternative that I found later is random-beans project. However, I did not have time to test it thoroughly. If you know other tools for generating and populating beans feel free to share your experience in comments.