How do I mock an autowired Value field in Spring with Mockito

Question

I m using Spring 3 1 4 RELEASE and Mockito 1 9 5   In my Spring class I have    Value    myProps  default url      private String defaultUrl    Value    myProps  default password      private String defaultrPassword            From my JUnit test  which I currently have set up like so    RunWith SpringJUnit4ClassRunner class   ContextConfiguration    classpath test-context xml     public class MyTest       I would like to mock a value for my  defaultUrl  field   Note that I don t want to mock values for the other fields     I d like to keep those as they are  only the  defaultUrl  field   Also note that I have no explicit  setter  methods  e g  setDefaultUrl  in my class and I don t want to create any just for the purposes of testing   Given this  how can I mock a value for that one field

User · Answer

Whenever possible  I set the field visibility as package-protected so it can be accessed from the test class  I document that using Guava s  VisibleForTesting annotation  in case the next guy wonders why it s not private   This way I don t have to rely on the string name of the field and everything stays type-safe  I know it goes against standard encapsulation practices we were taught in school  But as soon as there is some agreement in the team to go this way  I found it the most pragmatic solution

User · Answer

It was now the third time I googled myself to this SO post as I always forget how to mock an  Value field  Though the accepted answer is correct  I always need some time to get the  setField  call right  so at least for myself I paste an example snippet here   Production class    Value    myProps    some default url      private String defaultUrl    Test class   import org springframework test util ReflectionTestUtils   ReflectionTestUtils setField instanceUnderTest   defaultUrl    http   foo       Note  Don t use MyClassUnderTest class  use the instance you are testing itself    Note  Don t use the referenced string    myProps    some default url                but simply the FIELDs name   defaultUrl

User · Answer

You can use this magic Spring Test annotation      TestPropertySource properties      my spring property 20        see  org springframework test context TestPropertySource  For example  this is the test class     ContextConfiguration classes     MyTestClass Config class     TestPropertySource properties      my spring property 20     public class MyTestClass      public static class Config        Bean     MyClass getMyClass           return new MyClass                   Resource   private MyClass myClass       Test   public void myTest              And this is the class with the property     Component public class MyClass       Value    my spring property      private int mySpringProperty

User · Answer

You can also mock your property configuration into your test class   RunWith SpringJUnit4ClassRunner class   ContextConfiguration    classpath test-context xml     public class MyTest         Configuration    public static class MockConfig          Bean        public Properties myProps                 Properties properties   new Properties                 properties setProperty  default url    myUrl                 properties setProperty  property value2    value2                 return properties                     Value    myProps  default url         private String defaultUrl       Test    public void testValue           Assert assertEquals  myUrl   defaultUrl

User · Answer

I used the below code and it worked for me    InjectMocks private ClassABC classABC    Before public void setUp         ReflectionTestUtils setField classABC   constantFromConfigFile   3       Reference  https   www jeejava com mock-an-autowired-value-field-in-spring-with-junit-mockito

User · Answer

You can use the magic of Spring s ReflectionTestUtils setField in order to avoid making any modifications whatsoever to your code  The comment from Michal Stochmal provides an example   use ReflectionTestUtils setField bean   quot fieldName quot    quot value quot    before invoking your bean method during test   Check out this tutorial for even more information  although you probably won t need it since the method is very easy to use UPDATE Since the introduction of Spring 4 2 RC1 it is now possible to set a static field without having to supply an instance of the class  See this part of the documentation and this commit

User · Answer

Also note that I have no explicit  setter  methods  e g  setDefaultUrl  in my class and I don t want to create any just for the purposes of testing    One way to resolve this is change your class to use Constructor Injection  that is used for testing and Spring injection  No more reflection     So  you can pass any String using the constructor   class MySpringClass        private final String defaultUrl      private final String defaultrPassword       public MySpringClass             Value    myProps  default url      String defaultUrl             Value    myProps  default password      String defaultrPassword            this defaultUrl   defaultUrl          this defaultrPassword  defaultrPassword             And in your test  just use it   MySpringClass MySpringClass    new MySpringClass  anyUrl    anyPassword

User · Answer

I d like to suggest a related solution  which is to pass the  Value-annotated fields as parameters to the constructor  instead of using the ReflectionTestUtils class     Instead of this   public class Foo         Value    foo        private String foo      and  public class FooTest         InjectMocks     private Foo foo        Before     public void setUp             ReflectionTestUtils setField Foo class   foo    foo                Test     public void testFoo                stuff           Do this   public class Foo        private String foo       public Foo  Value    foo    String foo            this foo   foo            and  public class FooTest        private Foo foo        Before     public void setUp             foo   new Foo  foo                Test     public void testFoo                stuff           Benefits of this approach  1  we can instantiate the Foo class without a dependency container  it s just a constructor   and 2  we re not coupling our test to our implementation details  reflection ties us to the field name using a string  which could cause a problem if we change the field name

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