如何使用when（）…解决Mockito丢失MethodInvocationException？

Question

MissingMethodInvocationException：when（）需要一个必须是“mock上的方法调用”的参数。例如：when（mock.getarticles（））.ThenReturn（articles）；

此外，出现此错误的原因可能是：1。您使用final/private/equals()/hashCode（）方法中的任一个作为存根。这些方法不能被截取/验证。2.内部when（）不是对mock而是对其他对象调用method。

我的测试：

class ValidateBookResultsTests {

public static ArrayList<Book> searchResults = new ArrayList<Book>();
public static List<Book> topFive;
public static ArrayList<String> authors = new ArrayList<String>();

public static Book book1;
public static Book book2;
public static Book book3;
public static Book book4;
public static Book book5;
public static Book book6;

@BeforeEach
public void setUp() {
    book1 = new Book("title1", authors, "publisher1");
    book2 = new Book("title2", authors, "publisher2");
    book3 = new Book("title3", authors, "publisher3");
    book4 = new Book("title4", authors, "publisher4");
    book5 = new Book("title5", authors, "publisher5");
    book6 = new Book("title6", authors, "publisher6");

    searchResults.add(book1);
    searchResults.add(book2);
    searchResults.add(book3);
    searchResults.add(book4);
    searchResults.add(book5);
    searchResults.add(book6);
}

@Test
public void returnFiveBooksFromSearchResults() {
    authors.add("John Doe");
    authors.add("Bill Gates");

    BookSearch mockBookSearch = Mockito.mock(BookSearch.class);
    Mockito.when(mockBookSearch.returnFiveBooks(searchResults)).thenReturn(topFive);

    System.out.println("return books: " + mockBookSearch.returnFiveBooks(searchResults));
    System.out.println("top: "+ topFive);

    assertEquals(topFive.size(), 5);
 }
}

public static List<Book> returnFiveBooks(ArrayList<Book> searchResults) {
  Collections.shuffle(searchResults);
  topFive = searchResults.subList(0, 5);

  printFiveResults();

  return topFive; }

Answer 1

错误消息告诉您，您的方法调用不是模拟上的方法调用。

org.mockito.exceptions.misusing.MissingMethodInvocationException: 
when() requires an argument which has to be 'a method call on a mock'.
For example:
    when(mock.getArticles()).thenReturn(articles);

为什么？因为您正在尝试模拟静态方法。

Mockito.when(mockBookSearch.returnFiveBooks(searchResults)).thenReturn(topFive);

这相当于：

Mockito.when(BookSearch.returnFiveBooks(searchResults)).thenReturn(topFive);

@Test
public void returnFiveBooksFromSearchResults() {
    var topFive = BookSearch.returnFiveBooks(searchResults);
    assertEquals(topFive.size(), 5);
}