code: public CallActivityMock onExecutionSetVariables(final VariableMap variables){
      return this.onExecutionDo("setVariablesServiceMock_"+ randomUUID(),
        (execution) -> execution.setVariables(variables)
      );
    }
docs: On execution, the MockProcess will set the given VariableMap to the execution
  (ATTENTION: This means all current process variables are replaced with the given Map!)
  
  @param variables variables to set
  @return this mock instance