InvoiceFilter.java

package nl.tudelft.mocks;

import java.util.ArrayList;
import java.util.List;
import java.util.Queue;

public class InvoiceFilter {


    private InvoiceDao invoiceDao;

    public InvoiceFilter(InvoiceDao invoiceDao) {
        this.invoiceDao = invoiceDao;
    }

    public List<Invoice> filter() {

        List<Invoice> filtered = new ArrayList<>();

        List<Invoice> allInvoices = invoiceDao.all();

        for(Invoice inv : allInvoices) {
            if(inv.getValue() < 100.0)
                filtered.add(inv);
        }

        return filtered;

    }
}

InvoiceFilterTest.java

package nl.tudelft.mocks;


import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

import org.junit.jupiter.api.Test;
import org.mockito.Mockito;

import java.util.Arrays;
import java.util.List;

public class InvoiceFilterTest {


    @Test
    void filterInvoices() {

        InvoiceDao dao = mock(InvoiceDao.class);

        Invoice mauricio = new Invoice("Mauricio", 20.0);
        Invoice arie = new Invoice("Arie", 300.0);

        List<Invoice> fakeInvoices = Arrays.asList(mauricio, arie);

        when(dao.all()).thenReturn(fakeInvoices);

        InvoiceFilter filter = new InvoiceFilter(dao);
        List<Invoice> result = filter.filter();

        assertThat(result).containsExactly(mauricio);

    }
}