Mocking SAP S/4HANA Calls

In automated unit testing, it is sometimes necessary to use objects or procedures that look and behave like their release-intended counterparts, but are actually simplified versions that reduce complexity and facilitate testing. Such procedures are called test doubles. Mocking refers to the idea of providing these test doubles instead of the real implementation during tests. This helps in reducing the testing effort in cases where testing could be too cumbersome, or it is not possible to instantiate the entire program.

Furthermore, as we discussed with the testing pyramid, doing more unit tests is preferable during the development of the application as it forces application developers to write more testable application code and apply separation of concerns more thoroughly, which usually leads to more maintainable and understandable code. Using mocking and the tools provided by SAP Cloud SDK, we can test a small portion of the code without the need for a real SAP S/4HANA back-end system. This provides a very convenient way to test the overall functionality.

The MockUtil is a mocking utility class; it is provided by the SAP Cloud SDK. The MockUtil class helps create the mock instances required to simulate instances. The MockUtil class provided by the SAP Cloud SDK can also deal with connectivity to an SAP S/4HANA back-end.

To implement mocking using the MockUtil class (in Java), you need to:

• Create a new test file under your project location – <project>/unit-tests/src/test/java
• Initialize the mocking facility MockUtil provided by the SAP Cloud SDK
• Declare an initialization method beforeClass() which is annotated with @BeforeClass. This means that this method is called exactly once before the execution of all other test methods. Inside the method, all the required SAP Cloud Platform mocks are initialized (tenant, user, etc)
• Inside the method beforeClass(), mock a dummy SAP S/4HANA destination
• Inside the method beforeClass(), initialize the testing parameters
• Lastly add another method inside the newly created file to do the actual first testing. Inside this method we do the actual mocking by defining under which condition what should happen

Consider our existing Business Partner Address Manager application. In the GetAllBusinessPartnersCommand command, the run() method does a type-safe OData call to the BusinessPartner API of the SAP S/4HANA system. This fetches the business partner details and address. To view the code, navigate to your project and choose address-manager → application → src → main → java.

When it comes to mocking, this piece of code is tested locally rather than against a real SAP S/4HANA system. To achieve this, we add a new test command under the unit-tests directory. To access the unit-tests directory, choose address-manager → unit-tests → src → test → java.

import com.sap.cloud.sdk.odatav2.connectivity.ODataException;
import com.google.common.collect.Lists;
import com.sap.cloud.sdk.testutil.MockUtil;
import org.mockito.junit.MockitoJUnitRunner;

import static org.junit.Assert.*;
import static org.mockito.Mockito.*;

public class GetBusinessPartnerMockedTest
{
private static final MockUtil mockUtil = new MockUtil();
private static BusinessPartner tom;
private static BusinessPartner kathy;

@BeforeClass
public static void beforeClass() throws Exception {
mockUtil.mockDefaults();
mockUtil.mockDestination("ErpQueryEndpoint", URI.create(""));

tom = new BusinessPartner();
tom.setFirstName("Tom");

kathy = new BusinessPartner();
kathy.setFirstName("Kathy");
}

@Test
public void testGetAnyBusinessPartner() throws Exception
{
final BusinessPartnerService service = Mockito.mock(BusinessPartnerService.class, RETURNS_DEEP_STUBS);

when(service.getAllBusinessPartner()
.filter(any(ExpressionFluentHelper.class))
.select(any(EntityField.class))
.execute(any(ErpConfigContext.class)))
.thenReturn(Lists.newArrayList(tom, kathy));

final List businessPartnerList = new GetAllBusinessPartnersCommand(new ErpConfigContext(), service).execute();

assertEquals(2, businessPartnerList.size());
assertEquals("Tom", businessPartnerList.get(0).getFirstName());
assertEquals("Kathy", businessPartnerList.get(1).getFirstName());
}
}

The following table explains what happens in this piece of code:

private static final MockUtil mockUtil = new MockUtil();

private static BusinessPartner tom;
private static BusinessPartner kathy;

@BeforeClass
public static void beforeClass() throws Exception {
mockUtil.mockDefaults();
mockUtil.mockDestination("ErpQueryEndpoint", URI.create(""));

tom = new BusinessPartner();
tom.setFirstName("Tom");

kathy = new BusinessPartner();
kathy.setFirstName("Kathy");

final BusinessPartnerService service = Mockito.mock(BusinessPartnerService.class, RETURNS_DEEP_STUBS);

when(service.getAllBusinessPartner()
.filter(any(ExpressionFluentHelper.class))
.select(any(EntityField.class))
.execute(any(ErpConfigContext.class)))
.thenReturn(Lists.newArrayList(tom, kathy));

final List businessPartnerList = new GetAllBusinessPartnersCommand (new ErpConfigContext(), service).execute();

assertEquals(2, businessPartnerList.size());
assertEquals("Tom", businessPartnerList.get(0).getFirstName());
assertEquals("Kathy", businessPartnerList.get(1).getFirstName());