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改进这个问题
我是java&ood新手，一直在尝试为一个小型jdbc项目编写一些测试，但是在获得greenlight的测试时遇到了问题。我就是从这里开始的，玩了很多也没用。
这是我的测试：

@Test // 3
public void testThatWhenIAddACustomerThatWHenICallTheGetCustomerMethodInCustomerDAOItReturnsTheUser() {

    CustomerDAO customerDAO = new CustomerDAO();
    customerDAO.setEntityManager(entityManager);
    Customer customer = new Customer();
    Customer.setUsername("Customer1");
    customerDAO.addCustomer(customer);

    Customer customerInDB = customerDAO.getCustomer("Customer1");
    String usernameInDB = customerInDB.getUsername();
    assertEquals("Customer1", customerInDB);

}

我的刀：

public void addCustomer(Customer customer) {
    EntityTransaction entityTransaction = entityManager.getTransaction();
    entityTransaction.begin();
    entityManager.persist(customer);
    entityTransaction.commit();

}

public Customer getCustomer(String username) {
    Customer customerInDB = entityManager.find(Customer.class, username);
    return customerInDB;
}

public void removeCustomer(String username) {

    Customer customerInDB = entityManager.find(Customer.class, username);

    EntityTransaction entityTransaction = entityManager.getTransaction();
    entityTransaction.begin();

    entityManager.remove(customerInDB);
    entityTransaction.commit();

}

我的客户类别：

@Entity public class Customer {
@Id public String username;

private int customerId;
private double customerBalance;
private String firstName;
private String lastName;
private String email;

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}