How to unit test abstract classes extend with stubs

Question

I was wondering how to unit test abstract classes  and classes that extend abstract classes   Should I test the abstract class by extending it  stubbing out the abstract methods  and then test all the concrete methods  Then only test the methods I override  and test the abstract methods in the unit tests for objects that extend my abstract class   Should I have an abstract test case that can be used to test the methods of the abstract class  and extend this class in my test case for objects that extend the abstract class   Note that my abstract class has some concrete methods

User · Answer

one way is to write an abstract test case that corresponds to your abstract class, then write concrete test cases that subclass your abstract test case. do this for each concrete subclass of your original abstract class (i.e. your test case hierarchy mirrors your class hierarchy). see Test an interface in the junit recipies book: http://safari.informit.com/9781932394238/ch02lev1sec6. https://www.manning.com/books/junit-recipes or https://www.amazon.com/JUnit-Recipes-Practical-Methods-Programmer/dp/1932394230 if you don't have a safari account.

also see Testcase Superclass in xUnit patterns: http://xunitpatterns.com/Testcase%20Superclass.html

User · Answer

There are two ways in which abstract base classes are used    You are specializing your abstract object  but all clients will use the derived class through its base interface  You are using an abstract base class to factor out duplication within objects in your design  and clients use the concrete implementations through their own interfaces       Solution For 1 - Strategy Pattern    If you have the first situation  then you actually have an interface defined by the virtual methods in the abstract class that your derived classes are implementing    You should consider making this a real interface  changing your abstract class to be concrete  and take an instance of this interface in its constructor  Your derived classes then become implementations of this new interface      This means you can now test your previously abstract class using a mock instance of the new interface  and each new implementation through the now public interface  Everything is simple and testable     Solution For 2  If you have the second situation  then your abstract class is working as a helper class      Take a look at the functionality it contains  See if any of it can be pushed onto the objects that are being manipulated to minimize this duplication  If you still have anything left  look at making it a helper class that your concrete implementation take in their constructor and remove their base class      This again leads to concrete classes that are simple and easily testable     As a Rule  Favor complex network of simple objects over a simple network of complex objects   The key to extensible testable code is small building blocks and independent wiring     Updated   How to handle mixtures of both   It is possible to have a base class performing both of these roles    ie  it has a public interface  and has protected helper methods  If this is the case  then you can factor out the helper methods into one class  scenario2  and convert the inheritance tree into a strategy pattern    If you find you have some methods your base class implements directly and other are virtual  then you can still convert the inheritance tree into a strategy pattern  but I would also take it as a good indicator that the responsibilities are not correctly aligned  and may need refactoring      Update 2   Abstract Classes as a stepping stone  2014 06 12    I had a situation the other day where I used abstract  so I d like to explore why    We have a standard format for our configuration files  This particular tool has 3 configuration files all in that format  I wanted a strongly typed class for each setting file so  through dependency injection  a class could ask for the settings it cared about    I implemented this by having an abstract base class that knows how to parse the settings files formats and derived classes that exposed those same methods  but encapsulated the location of the settings file    I could have written a  SettingsFileParser  that the 3 classes wrapped  and then delegated through to the base class to expose the data access methods  I chose not to do this yet as it would lead to 3 derived classes with more delegation code in them than anything else    However    as this code evolves and the consumers of each of these settings classes become clearer  Each settings users will ask for some settings and transform them in some way  as settings are text they may wrap them in objects of convert them to numbers etc    As this happens I will start to extract this logic into data manipulation methods and push them back onto the strongly typed settings classes  This will lead to a higher level interface for each set of settings  that is eventually no longer aware it s dealing with  settings     At this point the strongly typed settings classes will no longer need the  getter  methods that expose the underlying  settings  implementation   At that point I would no longer want their public interface to include the settings accessor methods  so I will change this class to encapsulate a settings parser class instead of derive from it    The Abstract class is therefore  a way for me to avoid delegation code at the moment  and a marker in the code to remind me to change the design later  I may never get to it  so it may live a good while    only the code can tell   I find this to be true with any rule    like  no static methods  or  no private methods   They indicate a smell in the code    and that s good  It keeps you looking for the abstraction that you have missed    and lets you carry on providing value to your customer in the mean time    I imagine rules like this one defining a landscape  where maintainable code lives in the valleys  As you add new behaviour  it s like rain landing on your code  Initially you put it wherever it lands   then you refactor to allow the forces of good design to push the behaviour around until it all ends up in the valleys

User · Answer

If your abstract class contains concrete functionality that has business value  then I will usually test it directly by creating a test double that stubs out the abstract data  or by using a mocking framework to do this for me  Which one I choose depends a lot on whether I need to write test-specific implementations of the abstract methods or not   The most common scenario in which I need to do this is when I m using the Template Method pattern  such as when I m building some sort of extensible framework that will be used by a 3rd party  In this case  the abstract class is what defines the algorithm that I want to test  so it makes more sense to test the abstract base than a specific implementation   However  I think it s important that these tests should focus on the concrete implementations of real business logic only  you shouldn t unit test implementation details of the abstract class because you ll end up with brittle tests

User · Answer

This is the pattern I usually follow when setting up a harness for testing an abstract class   public abstract class MyBase              public abstract void VoidMethod object param1     public abstract object MethodWithReturn object param1                 And the version I use under test   public class MyBaseHarness   MyBase              public Action lt object gt  VoidMethodFunction    public override void VoidMethod object param1       VoidMethodFunction param1         public Func lt object  object gt  MethodWithReturnFunction    public override object MethodWithReturn object param1       return MethodWihtReturnFunction param1                     If the abstract methods are called when I don t expect it  the tests fail   When arranging the tests  I can easily stub out the abstract methods with lambdas that perform asserts  throw exceptions  return different values  etc

User · Answer

If an abstract class is appropriate for your implementation  test  as suggested above  a derived concrete class  Your assumptions are correct   To avoid future confusion  be aware that this concrete test class is not a mock  but a fake   In strict terms  a mock is defined by the following characteristics    A mock is used in place of each and every dependency of the subject class being tested  A mock is a pseudo-implementation of an interface  you may recall that as a general rule  dependencies should be declared as interfaces  testability is one primary reason for this  Behaviors of the mock s interface members -- whether methods or properties  -- are supplied at test-time  again  by use of a mocking framework   This way  you avoid coupling of the implementation being tested with the implementation of its dependencies  which should all have their own discrete tests

User · Answer

To make an unit test specifically on the abstract class  you should derive it for testing purpose  test base method   results and intended behaviour when inheriting   You test a method by calling it so test an abstract class by implementing it

User · Answer

There are two ways in which abstract base classes are used    You are specializing your abstract object  but all clients will use the derived class through its base interface  You are using an abstract base class to factor out duplication within objects in your design  and clients use the concrete implementations through their own interfaces       Solution For 1 - Strategy Pattern    If you have the first situation  then you actually have an interface defined by the virtual methods in the abstract class that your derived classes are implementing    You should consider making this a real interface  changing your abstract class to be concrete  and take an instance of this interface in its constructor  Your derived classes then become implementations of this new interface      This means you can now test your previously abstract class using a mock instance of the new interface  and each new implementation through the now public interface  Everything is simple and testable     Solution For 2  If you have the second situation  then your abstract class is working as a helper class      Take a look at the functionality it contains  See if any of it can be pushed onto the objects that are being manipulated to minimize this duplication  If you still have anything left  look at making it a helper class that your concrete implementation take in their constructor and remove their base class      This again leads to concrete classes that are simple and easily testable     As a Rule  Favor complex network of simple objects over a simple network of complex objects   The key to extensible testable code is small building blocks and independent wiring     Updated   How to handle mixtures of both   It is possible to have a base class performing both of these roles    ie  it has a public interface  and has protected helper methods  If this is the case  then you can factor out the helper methods into one class  scenario2  and convert the inheritance tree into a strategy pattern    If you find you have some methods your base class implements directly and other are virtual  then you can still convert the inheritance tree into a strategy pattern  but I would also take it as a good indicator that the responsibilities are not correctly aligned  and may need refactoring      Update 2   Abstract Classes as a stepping stone  2014 06 12    I had a situation the other day where I used abstract  so I d like to explore why    We have a standard format for our configuration files  This particular tool has 3 configuration files all in that format  I wanted a strongly typed class for each setting file so  through dependency injection  a class could ask for the settings it cared about    I implemented this by having an abstract base class that knows how to parse the settings files formats and derived classes that exposed those same methods  but encapsulated the location of the settings file    I could have written a  SettingsFileParser  that the 3 classes wrapped  and then delegated through to the base class to expose the data access methods  I chose not to do this yet as it would lead to 3 derived classes with more delegation code in them than anything else    However    as this code evolves and the consumers of each of these settings classes become clearer  Each settings users will ask for some settings and transform them in some way  as settings are text they may wrap them in objects of convert them to numbers etc    As this happens I will start to extract this logic into data manipulation methods and push them back onto the strongly typed settings classes  This will lead to a higher level interface for each set of settings  that is eventually no longer aware it s dealing with  settings     At this point the strongly typed settings classes will no longer need the  getter  methods that expose the underlying  settings  implementation   At that point I would no longer want their public interface to include the settings accessor methods  so I will change this class to encapsulate a settings parser class instead of derive from it    The Abstract class is therefore  a way for me to avoid delegation code at the moment  and a marker in the code to remind me to change the design later  I may never get to it  so it may live a good while    only the code can tell   I find this to be true with any rule    like  no static methods  or  no private methods   They indicate a smell in the code    and that s good  It keeps you looking for the abstraction that you have missed    and lets you carry on providing value to your customer in the mean time    I imagine rules like this one defining a landscape  where maintainable code lives in the valleys  As you add new behaviour  it s like rain landing on your code  Initially you put it wherever it lands   then you refactor to allow the forces of good design to push the behaviour around until it all ends up in the valleys

User · Answer

one way is to write an abstract test case that corresponds to your abstract class, then write concrete test cases that subclass your abstract test case. do this for each concrete subclass of your original abstract class (i.e. your test case hierarchy mirrors your class hierarchy). see Test an interface in the junit recipies book: http://safari.informit.com/9781932394238/ch02lev1sec6. https://www.manning.com/books/junit-recipes or https://www.amazon.com/JUnit-Recipes-Practical-Methods-Programmer/dp/1932394230 if you don't have a safari account.

also see Testcase Superclass in xUnit patterns: http://xunitpatterns.com/Testcase%20Superclass.html

User · Answer

To make an unit test specifically on the abstract class  you should derive it for testing purpose  test base method   results and intended behaviour when inheriting   You test a method by calling it so test an abstract class by implementing it

User · Answer

This is the pattern I usually follow when setting up a harness for testing an abstract class   public abstract class MyBase              public abstract void VoidMethod object param1     public abstract object MethodWithReturn object param1                 And the version I use under test   public class MyBaseHarness   MyBase              public Action lt object gt  VoidMethodFunction    public override void VoidMethod object param1       VoidMethodFunction param1         public Func lt object  object gt  MethodWithReturnFunction    public override object MethodWithReturn object param1       return MethodWihtReturnFunction param1                     If the abstract methods are called when I don t expect it  the tests fail   When arranging the tests  I can easily stub out the abstract methods with lambdas that perform asserts  throw exceptions  return different values  etc

User · Answer

Write a Mock object and use them just for testing  They usually are very very very minimal  inherit from the abstract class  and not more Then  in your Unit Test you can call the abstract method you want to test   You should test abstract class that contain some logic like all other classes you have

User · Answer

If your abstract class contains concrete functionality that has business value  then I will usually test it directly by creating a test double that stubs out the abstract data  or by using a mocking framework to do this for me  Which one I choose depends a lot on whether I need to write test-specific implementations of the abstract methods or not   The most common scenario in which I need to do this is when I m using the Template Method pattern  such as when I m building some sort of extensible framework that will be used by a 3rd party  In this case  the abstract class is what defines the algorithm that I want to test  so it makes more sense to test the abstract base than a specific implementation   However  I think it s important that these tests should focus on the concrete implementations of real business logic only  you shouldn t unit test implementation details of the abstract class because you ll end up with brittle tests

User · Answer

I suppose you could want to test the base functionality of an abstract class    But you d probably be best off by extending the class without overriding any methods  and make minimum-effort mocking for the abstract methods

User · Answer

What I do for abstract classes and interfaces is the following  I write a test  that uses the object as it is concrete  But the variable of type X  X is the abstract class  is not set in the test  This test-class is not added to the test-suite  but subclasses of it  that have a setup-method that set the variable to a concrete implementation of X  That way I don t duplicate the test-code  The subclasses of the not used test can add more test-methods if needed

User · Answer

What I do for abstract classes and interfaces is the following  I write a test  that uses the object as it is concrete  But the variable of type X  X is the abstract class  is not set in the test  This test-class is not added to the test-suite  but subclasses of it  that have a setup-method that set the variable to a concrete implementation of X  That way I don t duplicate the test-code  The subclasses of the not used test can add more test-methods if needed

User · Answer

One of the main motivations for using an abstract class is to enable polymorphism within your application -- i e  you can substitute a different version at runtime   In fact  this is very much the same thing as using an interface except the abstract class provides some common plumbing  often referred to as a Template pattern   From a unit testing perspective  there are two things to consider    Interaction of your abstract class with it related classes   Using a mock testing framework is ideal for this scenario as it shows that your abstract class plays well with others  Functionality of derived classes   If you have custom logic that you ve written for your derived classes  you should test those classes in isolation    edit  RhinoMocks is an awesome mock testing framework that can generate mock objects at runtime by dynamically deriving from your class   This approach can save you countless hours of hand-coding derived classes

User · Answer

If the concrete methods invoke any of the abstract methods that strategy won t work  and you d want to test each child class behavior separately  Otherwise  extending it and stubbing the abstract methods as you ve described should be fine  again provided the abstract class concrete methods are decoupled from child classes

User · Answer

one way is to write an abstract test case that corresponds to your abstract class, then write concrete test cases that subclass your abstract test case. do this for each concrete subclass of your original abstract class (i.e. your test case hierarchy mirrors your class hierarchy). see Test an interface in the junit recipies book: http://safari.informit.com/9781932394238/ch02lev1sec6. https://www.manning.com/books/junit-recipes or https://www.amazon.com/JUnit-Recipes-Practical-Methods-Programmer/dp/1932394230 if you don't have a safari account.

also see Testcase Superclass in xUnit patterns: http://xunitpatterns.com/Testcase%20Superclass.html

User · Answer

This is the pattern I usually follow when setting up a harness for testing an abstract class   public abstract class MyBase              public abstract void VoidMethod object param1     public abstract object MethodWithReturn object param1                 And the version I use under test   public class MyBaseHarness   MyBase              public Action lt object gt  VoidMethodFunction    public override void VoidMethod object param1       VoidMethodFunction param1         public Func lt object  object gt  MethodWithReturnFunction    public override object MethodWithReturn object param1       return MethodWihtReturnFunction param1                     If the abstract methods are called when I don t expect it  the tests fail   When arranging the tests  I can easily stub out the abstract methods with lambdas that perform asserts  throw exceptions  return different values  etc

User · Answer

Following  patrick-desjardins answer  I implemented abstract and it s implementation class along with  Test as follows   Abstract class - ABC java  import java util ArrayList  import java util List   public abstract class ABC        abstract String sayHello         public List lt String gt  getList             final List lt String gt  defaultList   new ArrayList lt  gt             defaultList add  abstract class            return defaultList            As Abstract classes cannot be instantiated  but they can be subclassed  concrete class DEF java  is as follows   public class DEF extends ABC         Override     public String sayHello             return  Hello               Test class to test both abstract as well as non-abstract method   import org junit Before  import static org hamcrest MatcherAssert assertThat  import static org hamcrest Matchers empty  import static org hamcrest Matchers is  import static org hamcrest Matchers not  import static org hamcrest Matchers contains  import java util Collection  import java util List  import static org hamcrest Matchers equalTo   import org junit Test   public class DEFTest        private DEF def        Before     public void setup             def   new DEF                Test     public void add            String result   def sayHello            assertThat result  is equalTo  Hello                   Test     public void getList            List lt String gt  result   def getList            assertThat  Collection lt String gt   result  is not empty               assertThat result  contains  abstract class

User · Answer

I suppose you could want to test the base functionality of an abstract class    But you d probably be best off by extending the class without overriding any methods  and make minimum-effort mocking for the abstract methods

User · Answer

I suppose you could want to test the base functionality of an abstract class    But you d probably be best off by extending the class without overriding any methods  and make minimum-effort mocking for the abstract methods

User · Answer

If your abstract class contains concrete functionality that has business value  then I will usually test it directly by creating a test double that stubs out the abstract data  or by using a mocking framework to do this for me  Which one I choose depends a lot on whether I need to write test-specific implementations of the abstract methods or not   The most common scenario in which I need to do this is when I m using the Template Method pattern  such as when I m building some sort of extensible framework that will be used by a 3rd party  In this case  the abstract class is what defines the algorithm that I want to test  so it makes more sense to test the abstract base than a specific implementation   However  I think it s important that these tests should focus on the concrete implementations of real business logic only  you shouldn t unit test implementation details of the abstract class because you ll end up with brittle tests

User · Answer

I would argue against  abstract  tests  I think a test is a concrete idea and doesn t have an abstraction  If you have common elements  put them in helper methods or classes for everyone to use   As for testing an abstract test class  make sure you ask yourself what it is you re testing  There are several approaches  and you should find out what works in your scenario  Are you trying to test out a new method in your subclass  Then have your tests only interact with that method  Are you testing the methods in your base class  Then probably have a separate fixture only for that class  and test each method individually with as many tests as necessary

User · Answer

What I do for abstract classes and interfaces is the following  I write a test  that uses the object as it is concrete  But the variable of type X  X is the abstract class  is not set in the test  This test-class is not added to the test-suite  but subclasses of it  that have a setup-method that set the variable to a concrete implementation of X  That way I don t duplicate the test-code  The subclasses of the not used test can add more test-methods if needed

User · Answer

If the concrete methods invoke any of the abstract methods that strategy won t work  and you d want to test each child class behavior separately  Otherwise  extending it and stubbing the abstract methods as you ve described should be fine  again provided the abstract class concrete methods are decoupled from child classes

User · Answer

To make an unit test specifically on the abstract class  you should derive it for testing purpose  test base method   results and intended behaviour when inheriting   You test a method by calling it so test an abstract class by implementing it

User · Answer

If the concrete methods invoke any of the abstract methods that strategy won t work  and you d want to test each child class behavior separately  Otherwise  extending it and stubbing the abstract methods as you ve described should be fine  again provided the abstract class concrete methods are decoupled from child classes

User · Answer

If your abstract class contains concrete functionality that has business value  then I will usually test it directly by creating a test double that stubs out the abstract data  or by using a mocking framework to do this for me  Which one I choose depends a lot on whether I need to write test-specific implementations of the abstract methods or not   The most common scenario in which I need to do this is when I m using the Template Method pattern  such as when I m building some sort of extensible framework that will be used by a 3rd party  In this case  the abstract class is what defines the algorithm that I want to test  so it makes more sense to test the abstract base than a specific implementation   However  I think it s important that these tests should focus on the concrete implementations of real business logic only  you shouldn t unit test implementation details of the abstract class because you ll end up with brittle tests

User · Answer

One of the main motivations for using an abstract class is to enable polymorphism within your application -- i e  you can substitute a different version at runtime   In fact  this is very much the same thing as using an interface except the abstract class provides some common plumbing  often referred to as a Template pattern   From a unit testing perspective  there are two things to consider    Interaction of your abstract class with it related classes   Using a mock testing framework is ideal for this scenario as it shows that your abstract class plays well with others  Functionality of derived classes   If you have custom logic that you ve written for your derived classes  you should test those classes in isolation    edit  RhinoMocks is an awesome mock testing framework that can generate mock objects at runtime by dynamically deriving from your class   This approach can save you countless hours of hand-coding derived classes

User · Answer

If an abstract class is appropriate for your implementation  test  as suggested above  a derived concrete class  Your assumptions are correct   To avoid future confusion  be aware that this concrete test class is not a mock  but a fake   In strict terms  a mock is defined by the following characteristics    A mock is used in place of each and every dependency of the subject class being tested  A mock is a pseudo-implementation of an interface  you may recall that as a general rule  dependencies should be declared as interfaces  testability is one primary reason for this  Behaviors of the mock s interface members -- whether methods or properties  -- are supplied at test-time  again  by use of a mocking framework   This way  you avoid coupling of the implementation being tested with the implementation of its dependencies  which should all have their own discrete tests

User · Answer

One of the main motivations for using an abstract class is to enable polymorphism within your application -- i e  you can substitute a different version at runtime   In fact  this is very much the same thing as using an interface except the abstract class provides some common plumbing  often referred to as a Template pattern   From a unit testing perspective  there are two things to consider    Interaction of your abstract class with it related classes   Using a mock testing framework is ideal for this scenario as it shows that your abstract class plays well with others  Functionality of derived classes   If you have custom logic that you ve written for your derived classes  you should test those classes in isolation    edit  RhinoMocks is an awesome mock testing framework that can generate mock objects at runtime by dynamically deriving from your class   This approach can save you countless hours of hand-coding derived classes

User · Answer

What I do for abstract classes and interfaces is the following  I write a test  that uses the object as it is concrete  But the variable of type X  X is the abstract class  is not set in the test  This test-class is not added to the test-suite  but subclasses of it  that have a setup-method that set the variable to a concrete implementation of X  That way I don t duplicate the test-code  The subclasses of the not used test can add more test-methods if needed

User · Answer

To make an unit test specifically on the abstract class  you should derive it for testing purpose  test base method   results and intended behaviour when inheriting   You test a method by calling it so test an abstract class by implementing it

User · Answer

This is the pattern I usually follow when setting up a harness for testing an abstract class   public abstract class MyBase              public abstract void VoidMethod object param1     public abstract object MethodWithReturn object param1                 And the version I use under test   public class MyBaseHarness   MyBase              public Action lt object gt  VoidMethodFunction    public override void VoidMethod object param1       VoidMethodFunction param1         public Func lt object  object gt  MethodWithReturnFunction    public override object MethodWithReturn object param1       return MethodWihtReturnFunction param1                     If the abstract methods are called when I don t expect it  the tests fail   When arranging the tests  I can easily stub out the abstract methods with lambdas that perform asserts  throw exceptions  return different values  etc

User · Answer

I would argue against  abstract  tests  I think a test is a concrete idea and doesn t have an abstraction  If you have common elements  put them in helper methods or classes for everyone to use   As for testing an abstract test class  make sure you ask yourself what it is you re testing  There are several approaches  and you should find out what works in your scenario  Are you trying to test out a new method in your subclass  Then have your tests only interact with that method  Are you testing the methods in your base class  Then probably have a separate fixture only for that class  and test each method individually with as many tests as necessary

User · Answer

I suppose you could want to test the base functionality of an abstract class    But you d probably be best off by extending the class without overriding any methods  and make minimum-effort mocking for the abstract methods

User · Answer

Following  patrick-desjardins answer  I implemented abstract and it s implementation class along with  Test as follows   Abstract class - ABC java  import java util ArrayList  import java util List   public abstract class ABC        abstract String sayHello         public List lt String gt  getList             final List lt String gt  defaultList   new ArrayList lt  gt             defaultList add  abstract class            return defaultList            As Abstract classes cannot be instantiated  but they can be subclassed  concrete class DEF java  is as follows   public class DEF extends ABC         Override     public String sayHello             return  Hello               Test class to test both abstract as well as non-abstract method   import org junit Before  import static org hamcrest MatcherAssert assertThat  import static org hamcrest Matchers empty  import static org hamcrest Matchers is  import static org hamcrest Matchers not  import static org hamcrest Matchers contains  import java util Collection  import java util List  import static org hamcrest Matchers equalTo   import org junit Test   public class DEFTest        private DEF def        Before     public void setup             def   new DEF                Test     public void add            String result   def sayHello            assertThat result  is equalTo  Hello                   Test     public void getList            List lt String gt  result   def getList            assertThat  Collection lt String gt   result  is not empty               assertThat result  contains  abstract class

User · Answer

Write a Mock object and use them just for testing  They usually are very very very minimal  inherit from the abstract class  and not more Then  in your Unit Test you can call the abstract method you want to test   You should test abstract class that contain some logic like all other classes you have

User · Answer

Write a Mock object and use them just for testing  They usually are very very very minimal  inherit from the abstract class  and not more Then  in your Unit Test you can call the abstract method you want to test   You should test abstract class that contain some logic like all other classes you have

User · Answer

one way is to write an abstract test case that corresponds to your abstract class, then write concrete test cases that subclass your abstract test case. do this for each concrete subclass of your original abstract class (i.e. your test case hierarchy mirrors your class hierarchy). see Test an interface in the junit recipies book: http://safari.informit.com/9781932394238/ch02lev1sec6. https://www.manning.com/books/junit-recipes or https://www.amazon.com/JUnit-Recipes-Practical-Methods-Programmer/dp/1932394230 if you don't have a safari account.

also see Testcase Superclass in xUnit patterns: http://xunitpatterns.com/Testcase%20Superclass.html

User · Answer

First if abstract class contained some concrete method i think you should do this considered this example   public abstract class A           public boolean method 1                  concrete method which we have to test                 class B extends class A             override       public boolean method 1                    override same method as above                     class Test A            private static B b      reference object of the class B       Before     public void init                   b   new B                         Test      public void Test method 1                   b method 1     use some assertion statements

User · Answer

One of the main motivations for using an abstract class is to enable polymorphism within your application -- i e  you can substitute a different version at runtime   In fact  this is very much the same thing as using an interface except the abstract class provides some common plumbing  often referred to as a Template pattern   From a unit testing perspective  there are two things to consider    Interaction of your abstract class with it related classes   Using a mock testing framework is ideal for this scenario as it shows that your abstract class plays well with others  Functionality of derived classes   If you have custom logic that you ve written for your derived classes  you should test those classes in isolation    edit  RhinoMocks is an awesome mock testing framework that can generate mock objects at runtime by dynamically deriving from your class   This approach can save you countless hours of hand-coding derived classes

User · Answer

If the concrete methods invoke any of the abstract methods that strategy won t work  and you d want to test each child class behavior separately  Otherwise  extending it and stubbing the abstract methods as you ve described should be fine  again provided the abstract class concrete methods are decoupled from child classes

User · Answer

I would argue against  abstract  tests  I think a test is a concrete idea and doesn t have an abstraction  If you have common elements  put them in helper methods or classes for everyone to use   As for testing an abstract test class  make sure you ask yourself what it is you re testing  There are several approaches  and you should find out what works in your scenario  Are you trying to test out a new method in your subclass  Then have your tests only interact with that method  Are you testing the methods in your base class  Then probably have a separate fixture only for that class  and test each method individually with as many tests as necessary

User · Answer

Write a Mock object and use them just for testing  They usually are very very very minimal  inherit from the abstract class  and not more Then  in your Unit Test you can call the abstract method you want to test   You should test abstract class that contain some logic like all other classes you have

User · Answer

First if abstract class contained some concrete method i think you should do this considered this example   public abstract class A           public boolean method 1                  concrete method which we have to test                 class B extends class A             override       public boolean method 1                    override same method as above                     class Test A            private static B b      reference object of the class B       Before     public void init                   b   new B                         Test      public void Test method 1                   b method 1     use some assertion statements

User · Answer

I would argue against  abstract  tests  I think a test is a concrete idea and doesn t have an abstraction  If you have common elements  put them in helper methods or classes for everyone to use   As for testing an abstract test class  make sure you ask yourself what it is you re testing  There are several approaches  and you should find out what works in your scenario  Are you trying to test out a new method in your subclass  Then have your tests only interact with that method  Are you testing the methods in your base class  Then probably have a separate fixture only for that class  and test each method individually with as many tests as necessary

[java] How to unit test abstract classes: extend with stubs?

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