CODEWITHSUNDEEP
javajunitmockito
Jack
Jack

Reputation: 6620

When do we need to use verify method of Mockito?

I am new to Mockito, following this and am trying to find out what verify method does. It seems it is used to make sure the selected method is called once. I have the following code, and by looking at the code I can find out I am calling addBook method twice so why should I use verify? I mean in any case it is easy to make sure a method is called oncem so why should we use verify method?

String isbn = mockedBookDAL.addBook(book1);
        assertNotNull(isbn);
        isbn = mockedBookDAL.addBook(book1);
        assertNotNull(isbn);
        verify(mockedBookDAL).addBook(book1);
        assertEquals(book1.getIsbn(), isbn);

Upvotes: 1

Views: 958

Answers (1)

Max Fichtelmann
Max Fichtelmann

Reputation: 3504

imagine a class to manage an account:

public class Account {
  private Logger logger;
  public Account(Logger logger) {
    this.logger = logger;
  }
  ...

  public void withdraw(int amount) {
    ...
    logger.logWithdrawal(amount);
    ...
  }
}

so to test, that the withdrawal was indeed logged, you mock the logger and verify the interaction:

public class AccountTest {
  @Test
  public void withdrawalShouldBeLogged() {
    Logger logger = mock(Logger.class);
    Account cut = new Account(logger);

    int amount = 10;
    cut.withdraw(amount);

    verify(logger).logWithdrawal(amount);
  }
}

This form of asserting is also called a spy.

A further notice: you should generally assert only one thing per test method. Verifying a spy interaction would be that assertion, so you should generally not use verify and assert in the same method.

Upvotes: 4

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