Mocking an output port on UNIT TEST

[SMorettini]

Does Fprime provide a way to mock an output port on Unit tests? If yes, how?

I'll try to explain with a simple example:

Let's consider two components: Producer and Consumer.

• Producer has an output port called provideLastState
• Consumer has an input port called getLastState

The two-port are connected together. When Consumer calls the port getLastState, the Consumer put the last state inside a variable passed by reference called my_state. What I would like to do is to create a mock/fake of getLastStateso in the unit test of Consumer I can set the my_state as I prefer and test different behaviour of the Consumer based on the value of my_state.

[LeStarch]

Yes we do! https://nasa.github.io/fprime/UsersGuide/user/unit-testing.html

The unit test harness created by fprime-util impl --ut has stubbed port implementations for all ports on a component. Thus you can write whatever remote behavior you want and test the component in isolation.

In this example you'd create a test harness for Consumer and implement your mock state production in the test harness.

If you need more details to get started, please post back here!

[SMorettini]

Thank you for the answer. Could you give me some more details? I already tried to use the functions provided by TesterBase but I didn't find a way to solve the problem yet.

Should I implement my mock inside the following autogenerated function in Tester.cpp? Or I'm approaching the problem in a total wrong way?

  // ----------------------------------------------------------------------
  // Handlers for typed from ports
  // ----------------------------------------------------------------------

  void Tester ::
    from_getLastState_handler(
        const NATIVE_INT_TYPE portNum,
        Type::State state
    )
  {
    this->pushFromPortEntry_getLastState(state);
  }

[codeflight1]

You are approaching it the wrong way, you need to write a test in the Tester::toDo() function, and you can the use ASSERT_FROM_ to check the output. It might help to take a look at the MathComponent tutorial.

[kevin-f-ortega]

Should I implement my mock inside the following autogenerated function in Tester.cpp?

@SMorettini yes. If you want to mock the output port's behavior, then write it out inside the from_ autogenerated function in Tester.cpp.

[timcanham]

It also isn't uncommon if you need to implement special code for testing to augment what is in the handler. You can add your own code and even comment out the push() statement if you don't care. Tester.cpp was meant to be initially generated as a stub that the developer fills in. I frequently set up a condition in Tester.cpp, invoke the command or port that in turn invokes the handler, and then check the outcome. For instance, in your example (I modified the signature to have a reference to modify the state):

  // ----------------------------------------------------------------------
  // Handlers for typed from ports
  // ----------------------------------------------------------------------

  void Tester ::
    from_getLastState_handler(
        const NATIVE_INT_TYPE portNum,
        Type::State &state
    )
  {
    state = this->testState;
    this->pushFromPortEntry_getLastState(state);
  }

In the test case, you can do:

 ...
 this->testState = MY_STATE;
 this->invoke_to_someport(...); // this causes getLastState() port to be called
 ASSERT_TRUE(something that happened because state == MY_STATE)