Use Mockito to mock some methods but not others

Question

Is there any way  using Mockito  to mock some methods in a class  but not others   For example  in this  admittedly contrived  Stock class I want to mock the getPrice   and getQuantity   return values  as shown in the test snippet below  but I want the getValue   to perform the multiplication as coded in the Stock class  public class Stock     private final double price    private final int quantity     Stock double price  int quantity        this price   price      this quantity   quantity         public double getPrice         return price         public int getQuantity         return quantity        public double getValue         return getPrice     getQuantity            Test   public void getValueTest         Stock stock   mock Stock class       when stock getPrice    thenReturn 100 00       when stock getQuantity    thenReturn 200       double value   stock getValue           Unfortunately the following assert fails  because the mock Stock getValue   method does not perform the Stock getValue   calculation code      assertEquals  Stock value not correct   100 00 200  value   00001

User · Answer

Partial mocking using Mockito s spy method could be the solution to your problem  as already stated in the answers above  To some degree I agree that  for your concrete use case  it may be more appropriate to mock the DB lookup  From my experience this is not always possible - at least not without other workarounds - that I would consider as being very cumbersome or at least fragile  Note  that partial mocking does not work with ally versions of Mockito  You have use at least 1 8 0   I would have just written a simple comment for the original question instead of posting this answer  but StackOverflow does not allow this   Just one more thing  I really cannot understand that many times a question is being asked here gets comment with  Why you want to do this  without at least trying to understand the problem  Escpecially when it comes to then need for partial mocking there are really a lot of use cases that I could imagine where it would be useful  That s why the guys from Mockito provided that functionality  This feature should of course not be overused  But when we talk about test case setups that otherwise could not be established in a very complicated way  spying should be used

User · Answer

Partial mocking of a class is also supported via Spy in mockito  List list   new LinkedList    List spy   spy list      optionally  you can stub out some methods  when spy size    thenReturn 100      using the spy calls real methods spy add  one    spy add  two       size   method was stubbed - 100 is printed System out println spy size       Check the 1 10 19 and 2 7 22 docs for detailed explanation

User · Answer

According to docs    Foo mock   mock Foo class  CALLS REAL METHODS       this calls the real implementation of Foo getSomething   value   mock getSomething     when mock getSomething    thenReturn fakeValue       now fakeValue is returned value   mock getSomething

User · Answer

What you want is org mockito Mockito CALLS REAL METHODS according to the docs          Optional  lt code gt Answer lt  code gt  to be used with   link Mockito mock Class  Answer       lt p gt       link Answer  can be used to define the return values of unstubbed invocations      lt p gt     This implementation can be helpful when working with legacy code     When this implementation is used  unstubbed methods will delegate to the real implementation     This is a way to create a partial mock object that calls real methods by default      lt p gt     As usual you are going to read  lt b gt the partial mock warning lt  b gt      Object oriented programming is more less tackling complexity by dividing the complexity into separate  specific  SRPy objects     How does partial mock fit into this paradigm  Well  it just doesn t        Partial mock usually means that the complexity has been moved to a different method on the same object     In most cases  this is not the way you want to design your application      lt p gt     However  there are rare cases when partial mocks come handy      dealing with code you cannot change easily  3rd party interfaces  interim refactoring of legacy code etc      However  I wouldn t use partial mocks for new  test-driven  amp  well-designed code      lt p gt     Example      lt pre class  code  gt  lt code class  java  gt     Foo mock   mock Foo class  CALLS REAL METHODS            this calls the real implementation of Foo getSomething      value   mock getSomething          when mock getSomething    thenReturn fakeValue            now fakeValue is returned    value   mock getSomething        lt  code gt  lt  pre gt        Thus your code should look like   import org junit Test  import static org mockito Mockito    import static org junit Assert     public class StockTest        public class Stock           private final double price          private final int quantity           Stock double price  int quantity                this price   price              this quantity   quantity                     public double getPrice                 return price                     public int getQuantity                 return quantity                     public double getValue                 return getPrice     getQuantity                          Test     public void getValueTest             Stock stock   mock Stock class  withSettings   defaultAnswer CALLS REAL METHODS            when stock getPrice    thenReturn 100 00           when stock getQuantity    thenReturn 200           double value   stock getValue             assertEquals  Stock value not correct   100 00   200  value   00001               The call to Stock stock   mock Stock class   calls org mockito Mockito mock Class lt T gt   which looks like this    public static  lt T gt  T mock Class lt T gt  classToMock        return mock classToMock  withSettings   defaultAnswer RETURNS DEFAULTS        The docs of the value RETURNS DEFAULTS tell          The default  lt code gt Answer lt  code gt  of every mock  lt b gt if lt  b gt  the mock was not stubbed     Typically it just returns some empty value       lt p gt       link Answer  can be used to define the return values of unstubbed invocations       lt p gt     This implementation first tries the global configuration      If there is no global configuration then it uses   link ReturnsEmptyValues   returns zeros  empty collections  nulls  etc

User · Answer

To directly answer your question  yes  you can mock some methods without mocking others  This is called a partial mock  See the Mockito documentation on partial mocks for more information   For your example  you can do something like the following  in your test   Stock stock   mock Stock class   when stock getPrice    thenReturn 100 00         Mock implementation when stock getQuantity    thenReturn 200         Mock implementation when stock getValue    thenCallRealMethod        Real implementation   In that case  each method implementation is mocked  unless specify thenCallRealMethod   in the when     clause   There is also a possibility the other way around with spy instead of mock   Stock stock   spy Stock class   when stock getPrice    thenReturn 100 00         Mock implementation when stock getQuantity    thenReturn 200         Mock implementation    All other method call will use the real implementations   In that case  all method implementation are the real one  except if you have defined a mocked behaviour with when       There is one important pitfall when you use when Object  with spy like in the previous example  The real method will be called  because stock getPrice   is evaluated before when     at runtime   This can be a problem if your method contains logic that should not be called  You can write the previous example like this   Stock stock   spy Stock class   doReturn 100 00  when stock  getPrice          Mock implementation doReturn 200  when stock  getQuantity          Mock implementation    All other method call will use the real implementations     Another possibility may be to use org mockito Mockito CALLS REAL METHODS  such as   Stock MOCK STOCK   Mockito mock  Stock class  CALLS REAL METHODS      This delegates unstubbed calls to real implementations     However  with your example  I believe it will still fail  since the implementation of getValue   relies on quantity and price  rather than getQuantity   and getPrice    which is what you ve mocked   Another possibility is to avoid mocks altogether    Test public void getValueTest         Stock stock   new Stock 100 00  200       double value   stock getValue        assertEquals  Stock value not correct   100 00 200  value   00001

[java] Use Mockito to mock some methods but not others

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