import pluggy
import pytest
hookspec = pluggy.HookspecMarker("myproject")
hookimpl = pluggy.HookimplMarker("myproject")


class MySpec:
    """A hook specification namespace."""

    @hookspec
    def myhook(self, arg1, arg2):
        """My special little hook that you can customize."""


class Plugin_1:
    """A hook implementation namespace."""

    @hookimpl
    def myhook(self, arg1, arg2=1):
        print("inside Plugin_1.myhook()")
        return arg1 + arg2


class Plugin_2:
    """A 2nd hook implementation namespace."""

    @hookimpl
    def myhook(self, arg1, arg2=1):
        print("inside Plugin_2.myhook()")
        return arg1 - arg2


def test_case():
    # create a manager and add the spec
    pm = pluggy.PluginManager("myproject")
    pm.add_hookspecs(MySpec)

    # register plugins
    pm.register(Plugin_1())
    pm.register(Plugin_2())

    # call our ``myhook`` hook
    results = pm.hook.myhook(arg1=1, arg2=2)
    assert results == [1 - 2, 1 + 2]

(venv) PS C:\Code\DXN4\demo> pytest .\pluggy_demo2.py         
========================== test session starts ============================
        pm.register(Plugin_1())
        pm.register(Plugin_2())

        # call our ``myhook`` hook
        results = pm.hook.myhook(arg1=1, arg2=2)
>       assert results == [1 - 2, 1 + 2]
E       assert [0, 2] == [-1, 3]
E         At index 0 diff: 0 != -1
E         Use -v to get more diff

pluggy_demo2.py:44: AssertionError
--------------------------------------------------------------------------------------------------------------- Captured stdout call ---------------------------------------------------------------------------------------------------------------- 
inside Plugin_2.myhook()
inside Plugin_1.myhook()
======================== short test summary info ============================= 
FAILED pluggy_demo2.py::test_case - assert [0, 2] == [-1, 3]
========================== 1 failed in 0.15s ================================ 
(venv) PS C:\Code\DXN4\demo>