SupplySystem with test after refactoring

// AFTER REFACTORING:


package org.legacy;

import org.hamcrest.Matcher;
import org.junit.Before;
import org.junit.Test;
import org.mockito.ArgumentMatcher;
import org.mockito.Mockito;

public class SupplyMonitorTest {
    private SupplyMonitor underTest;
    private Inventory inventory = Mockito.mock(Inventory.class);
    private SupplySystemWrapper supplySystem = Mockito.mock(SupplySystemWrapper.class);
    private Matcher<PurchaseOrder> orderMatcher = new ArgumentMatcher<PurchaseOrder>() {
        @Override
        public boolean matches(Object argument) {
            PurchaseOrder order = (PurchaseOrder) argument;
            return SupplyMonitor.PENCIL_ITEM_CODE.equals(order.getItemCode())
                    && order.getQuantity() == 280;
        }
    };

    @Before
    public void setUp() throws Exception {
        underTest = new SupplyMonitor(inventory, 100, supplySystem);
    }


    @Test
    public void should_order_pencils_when_undersupplied() {
        Mockito.when(inventory.getItemCount(SupplyMonitor.PENCIL_ITEM_CODE)).thenReturn(120);
        underTest.trackAndProcurePencils();
        Mockito.verify(supplySystem).buy(Mockito.argThat(orderMatcher ), Mockito.any());
    }

}


//-------------------------------------------------------


package org.legacy;

public class SupplyMonitor {
    private static final int TARGET_PENCILS_PER_EMPLOYEE = 4;
    static final String PENCIL_ITEM_CODE = "123";
    private static final String CREDIT_CARD_NUMBER = "XXXX XXXX XXXX XXXX";
    private SupplySystemWrapper supplySystem;

    private Inventory inventory;
    private int currentEmployeeCount;

    // legacy constructor - to be deleted once all refererencing code has been
    // refactored
    public SupplyMonitor(Inventory inventory, int currentEmployeeCount) {
        super();
        this.inventory = inventory;
        this.currentEmployeeCount = currentEmployeeCount;

        // one new line to keep the old static call via the wrapper
        this.supplySystem = new SupplySystemWrapper() {
        };
    }

    // new constructor for tests
    public SupplyMonitor(Inventory inventory, int currentEmployeeCount, SupplySystemWrapper supplySystem) {
        super();
        this.supplySystem = supplySystem;
        this.inventory = inventory;
        this.currentEmployeeCount = currentEmployeeCount;
    }

    public void trackAndProcurePencils() {
        int targetPencilCount = this.currentEmployeeCount * TARGET_PENCILS_PER_EMPLOYEE;
        int currentPencilCount = inventory.getItemCount(PENCIL_ITEM_CODE);
        if (currentPencilCount < targetPencilCount) {
            // changed static call to wrapper call:
            this.supplySystem.buy(new PurchaseOrder(PENCIL_ITEM_CODE, targetPencilCount - currentPencilCount),
                    new CreditCard(CREDIT_CARD_NUMBER));
        }
    }
}