Spock - How to work with repeated interactions - unit-testing

Question

For few test cases I'm trying to follow a DRY principle, where only the interactions are different with same test case conditions. I'm not able to find a way to implement multiple methods in the interaction { } block.
As mentioned in http://spockframework.org/spock/docs/1.3/interaction_based_testing.html#_explicit_interaction_blocks, I'm using interaction { } in the then: block like below:
Java Code:
// legacy code (still running on EJB 1.0 framework, and no dependency injection involved)
// can't alter java code base
public voidGetData() {
DataService ds = new DataService();
ds = ds.findByOffset(5);
Long len = ds.getOffset() // happy path scenario; missing a null check
// other code
}
// other varieties of same code:
public voidGetData2() {
ItemEJB tmpItem = new ItemEJB();
ItemEJB item = tmpItem.findByOffset(5);
if(null != item) {
Long len = item.getOffset();
// other code
}
}
public voidGetData3() {
ItemEJB item = new ItemEJB().findByOffset(5);
if(null != item) {
Long len = item.getOffset();
// other code
}
}
Spock Test:
def "test scene1"() {
given: "a task"
// other code ommitted
DataService mockObj = Mock(DataService)
when: "take action"
// code omitted
then: "action response"
interaction {
verifyNoDataScenario() // How to add verifyErrorScenario() interaction to the list?
}
}
private verifyDataScenario() {
1 * mockObj.findByOffset(5) >> mockObj // the findByOffset() returns an object, so mapped to same mock instance
1 * mockObj.getOffset() >> 200
}
private verifyErrorScenario() {
1 * mockObj.findByOffset(5) >> null // the findByOffset() returns null
0 * mockObj.getOffset() >> 200 // this won't be executed, and should ie expected to throw NPE
}
The interaction closure doesn't accept more than one method call. I'm not sure if it's design limitation. I believe more can be done in the closure than just mentioning the method name. I also tried interpolating the mockObj as a variable and use data pipe / data table, but since it's referring the same mock instance, it's not working. I'll post that as a separate question.
I ended up repeating the test case twice just to invoke different interaction methods. Down the line I see more scenarios, and wanted to avoid copy & paste approach. Appreciate any pointers to achieve this.
Update:
Modified shared java code as the earlier DataService name was confusing.
As there's no DI involved, and I didn't find a way to mock method variables, so I mock them using PowerMockito, e.g. PowerMockito.whenNew(DataService.class).withNoArguments().thenReturn(mockObj)

Answer 1

Your application code looks very strange. Is the programming style in your legacy application really that bad? First a DataService object is created with a no-arguments constructor, just to be overwritten in the next step by calling a method on that instance which again returns a DataService object. What kind of programmer creates code like that? Or did you just make up some pseudo code which does not have much in common with your real application? Please explain.
As for your test code, it also does not make sense because you instantiate DataService mockObj as a local variable in your feature method (test method), which means that in your helper method mockObj cannot be accessed. So either you need to pass the object as a parameter to the helper methods or you need to make it a field in your test class.
Last, but not least, your local mock object is never injected into the class under test because, as I said in the first paragraph, the DataService object in getData() is also a local variable. Unless your application code is compeletely fake, there is no way to inject the mock because getData() does not have any method parameter and the DataService object is not a field which could be set via setter method or constructor. Thus, you can create as many mocks as you want, the application will never have any knowledge of them. So your stubbing findByOffset(long offset) (why don't you show the code of that method?) has no effect whatsoever.
Bottom line: Please provide an example reflecting the structure of your real code, both application and test code. The snippets you provide do not make any sense, unfortunately. I am trying to help, but like this I cannot.
Update:
In my comments I mentioned refactoring your legacy code for testability by adding a constructor, setter method or an overloaded getData method with an additional parameter. Here is an example of what I mean:
Dummy helper class:
package de.scrum_master.stackoverflow.q58470315;
public class DataService {
private long offset;
public DataService(long offset) {
this.offset = offset;
}
public DataService() {}
public DataService findByOffset(long offset) {
return new DataService(offset);
}
public long getOffset() {
return offset;
}
#Override
public String toString() {
return "DataService{" +
"offset=" + offset +
'}';
}
}
Subject under test:
Let me add a private DataService member with a setter in order to make the object injectable. I am also adding a check if the ds member has been injected or not. If not, the code will behave like before in production and create a new object by itself.
package de.scrum_master.stackoverflow.q58470315;
public class ToBeTestedWithInteractions {
private DataService ds;
public void setDataService(DataService ds) {
this.ds = ds;
}
// legacy code; can't alter
public void getData() {
if (ds == null)
ds = new DataService();
ds = ds.findByOffset(5);
Long len = ds.getOffset();
}
}
Spock test:
Now let us test both the normal and the error scenario. Actually I think you should break it down into two smaller feature methods, but as you seem to wish to test everything (IMO too much) in one method, you can also do that via two distinct pairs of when-then blocks. You do not need to explicitly declare any interaction blocks in order to do so.
package de.scrum_master.stackoverflow.q58470315
import spock.lang.Specification
class RepeatedInteractionsTest extends Specification {
def "test scene1"() {
given: "subject under test with injected mock"
ToBeTestedWithInteractions subjectUnderTest = new ToBeTestedWithInteractions()
DataService dataService = Mock()
subjectUnderTest.dataService = dataService
when: "getting data"
subjectUnderTest.getData()
then: "no error, normal return values"
noExceptionThrown()
1 * dataService.findByOffset(5) >> dataService
1 * dataService.getOffset() >> 200
when: "getting data"
subjectUnderTest.getData()
then: "NPE, only first method called"
thrown NullPointerException
1 * dataService.findByOffset(5) >> null
0 * dataService.getOffset()
}
}
Please also note that testing for exceptions thrown or not thrown adds value to the test, the interaction testing just checks internal legacy code behaviour, which has little to no value.