Spring + QueryDsl + Mockito: How to write a unit test case for a simple function - spring

Question

I have the following function in my service.
public boolean checkNameUnique(String name) {
QEntity qEntity = QEntity.entity;
BooleanExpression nameUniquePredicate = qEntity.name.eq(name);
long count = entityReadRepository.count(nameUniquePredicate);
return count == 0;
}
It just checks if the name already exists in db. That needs to be unique, so it returns true if does not already exist and false if it does.
Now how do I write a mockito unit test case for this? I am new to Mockito and writing unit test cases, hence the question.
My reading on Mockito has lead me to write something on the lines of
when(entityReadRepository.count(nameUniquePredicate)).thenReturn(1);
and then call the function to be tested. But that doesn't make any sense.
Entity is Hibernate entity which corresponds to a table in the DB
entityReadRepository extends JpaRepository and QueryDslPredicateExecutor. QEntity is the Q object generated by QueryDsl's plugin.

Answer 1

A unit test would normally mock out any external dependencies, in your case entityReadRepository. If you want to do actual db call it would be classed as integration test.
Your method should return two different values depending on the entityReadRepository response and this is what you would stub in order to unit test it. You were on a good path trying:
when(entityReadRepository.count(any(BooleanExpression.class))).thenReturn(1l);
The problem you have is that you have a lot of static calls and objects in your method and that can't be handled gracefully. One option is to use tools like Powermockito where you can mock behaviour of static methods. If you prefer to stick with mockito you could extract static piece of code to a separate method and create a spy of your class under test:
package com.slavpilus;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.Spy;
import org.mockito.runners.MockitoJUnitRunner;
import static org.mockito.Matchers.any;
import static org.mockito.Mockito.doReturn;
import static org.mockito.Mockito.when;
#RunWith(MockitoJUnitRunner.class)
public class TPresenterTest {
#InjectMocks
#Spy
private ClassUnderTest target = new ClassUnderTest();
#Before
public void setUp() {
doReturn(null).when(target).getUniqueNamePredicate();
}
#Mock
private YourRepositoryDependency entityReadRepository;
#Test
public void checkNameUniqueShouldBeTrueIfNameNotInDatabase() {
when(entityReadRepository.count(any())).thenReturn(0l);
boolean isUnique = target.checkNameUnique("anyName");
Assert.assertTrue(isUnique);
}
#Test
public void checkNameUniqueShouldBeFalseIfNameFoundInDatabase() {
when(entityReadRepository.count(any())).thenReturn(1l);
boolean isUnique = target.checkNameUnique("anyName");
Assert.assertFalse(isUnique);
}
}
and your production code would look something like that:
public boolean checkNameUnique(String name) {
BooleanExpression nameUniquePredicate = getUniqueNamePredicate();
long count = entityReadRepository.count(nameUniquePredicate);
return count == 0;
}
protected BooleanExpression getUniqueNamePredicate() {
QEntity qEntity = QEntity.entity;
return qEntity.name.eq(name);
}
This approach however leaves you with some code untested as getUniqueNamePredicate method is skipped entirely during the test execution.