如何在方法内部对新创建的对象进行单元测试？

Question

我有使用方法payWorkOrder（）的PaymentPresenter。该方法接受一些参数，并根据逻辑创建了两个新对象：

1. WoPayment
2. PaymentRequest

这里是代码：

public void payWorkOrderInvoice(int workOrderId, double amount, String paymentMethod, String checkNumber) {
disposables = RxUtil.initDisposables(disposables);

WoPayment woPayment = new WoPayment();

if(amount > 0) {
  woPayment.setAmount(amount);
} else {
  view.displayAmountShouldBeGreaterThanZero();
  return;
}

if(TextUtils.isEmpty(paymentMethod)) {
  view.displayPaymentMethodInvalid();
  return;
} else {
  woPayment.setPaymentMethod(paymentMethod);
}

if(paymentMethod.equalsIgnoreCase("Check") && TextUtils.isEmpty(checkNumber)) {
  view.displayReferenceNumberError();
  return;
} else {
  woPayment.setCheckNumber(checkNumber);
}

view.disablePayButton();

Disposable disposable = workOrdersRepository.payWorkOrderInvoice(workOrderId, new PaymentRequest(woPayment))
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(response -> {
      if(response.isSuccessful()) {
        view.displayWorkOrderInvoicePaid(response.body());
      } else {
        view.enablePayButton();
        view.displayWorkOrderInvoiceNotPaid();
      }
      }, throwable -> {
      view.enablePayButton();
      view.handleError(throwable);
    });

disposables.add(disposable);
}
}

这是我的单元测试：

@Test public void shouldPayWorkOrderInvoice() {
// Given
int workOrderId = 1;
double amount = 1.0;
String paymentMethod = "cash";
String checkNumber = "1";
WorkOrderDetails workOrderDetails = Mockito.mock(WorkOrderDetails.class);
Response<WorkOrderDetails> response = Response.success(200, workOrderDetails);
WoPayment woPayment = new WoPayment();
woPayment.setAmount(amount);
woPayment.setCheckNumber(checkNumber);
woPayment.setPaymentMethod(paymentMethod);
PaymentRequest paymentRequest = new PaymentRequest(woPayment);

// When
Mockito.when(workOrdersRepository.payWorkOrderInvoice(workOrderId, paymentRequest)).thenReturn(Single.just(response));
presenter.payWorkOrderInvoice(workOrderId, amount, paymentMethod, checkNumber);

// Then
Mockito.verify(view).displayWorkOrderInvoicePaid(workOrderDetails);
}

但是使用以下堆栈跟踪失败：

java.lang.NullPointerException在com.test.presentation.agreements.payment.PaymentPresenter.payWorkOrderInvoice（PaymentPresenter.java:168）在com.test.presentation.agreements.PaymentPresenterTest.shouldPayWorkOrderInvoice（PaymentPresenterTest.java:175）在sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）处sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:62）在sun.reflect.DelegatingMethodAccessorImpl.invoke（DelegatingMethodAccessorImpl.java:43）在java.lang.reflect.Method.invoke（Method.java:498）在org.junit.internal.runners.TestMethod.invoke（TestMethod.java:68）在org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl $ PowerMockJUnit44MethodRunner.runTestMethod（PowerMockJUnit44RunnerDelegateImpl.java:310）在org.junit.internal.runners.MethodRoadie $ 2.run（MethodRoadie.java:89）在org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters（MethodRoadie.java:97）在org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl $ PowerMockJUnit44MethodRunner.executeTest（PowerMockJUnit44RunnerDelegateImpl.java:294）在org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl $ PowerMockJUnit47MethodRunner.executeTestInSuper（PowerMockJUnit47RunnerDelegateImpl.java:127）在org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl $ PowerMockJUnit47MethodRunner.access $ 100（PowerMockJUnit47RunnerDelegateImpl.java:59）在org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl $ PowerMockJUnit47MethodRunner $ LastRuleTestExecutorStatement.evaluate（PowerMockJUnit47RunnerDelegateImpl.java:148）在com.test.presentation.core.TrampolineSchedulerRule $ 1.evaluate（TrampolineSchedulerRule.java:21）

Answer 1

[堆栈跟踪说，在第168行的PaymentPresenter.java文件中，可以访问'null'的对象，即未实例化。因此，请看该行并尝试找出为什么未实例化该对象的原因。没有文件的行号很难分辨。