java - How do we unit test this lambda expression? -

we have rest end point (jax-rs) invoked browser. passing around outputstream have browser display result of call.

here method.

@path("/mypath/{userid}") @post public response createuser(@pathparam("userid") final int userid ) {     streamingoutput stream = (outputstream) -> {         user user = userhelper.finduser(userid);         userhelper.updateuser(user,outputstream);     };      return response.ok(stream).build(); } 

using junit , mockito, how verify if userhelper.finduser , userhelper.updateuser has been called ?

basically want verify interactions.

to "unit" test should create test class , create new instance of class method belongs in test class. userhelper not defined in lambda class member? if can mocked:

• create mock userhelper object mockito
• inject mock test class.
• call createuser method.
• verify on mock assert updateuser method called once.
• you can go step further , verify user , outputstream objects passed using captors.