Fix pytest working dir in Pycharm (#199)

My unit tests assume cwd = /, in order to locate wav files.
But Pycharm uses the wrong working dir whenever you "rerun failed tests" or "run tests in file".
This runs `chdir(correct dir)`.

tests/conftest.py

@@ -6,6 +6,7 @@ Integration tests found in:
 
 import os
 import subprocess
+from pathlib import Path
 from typing import TYPE_CHECKING
 
 import pytest
@@ -14,6 +15,11 @@ if TYPE_CHECKING:
     import pytest_mock
 
 
+# Pycharm sets cwd to /tests/.
+# To ensure tests can find WAV files (based on /), jump from /tests/conftest.py to /.
+os.chdir(Path(__file__).parent.parent)
+
+
 @pytest.fixture
 def Popen(mocker: "pytest_mock.MockFixture"):
     real_Popen = subprocess.Popen