Improve test coverage and fix issue in path loading (#602)

* reactivate skipped tests

* remove unused internal interfaces

* enable pytest in VS Code

* simplify and fix path logic in loader

* increase test coverage

* test missing config

* check for wrong printer names

* Skipped appdir test

test/test_config.py

@@ -0,0 +1,126 @@
+#!/usr/bin/python
+"""tests for config module
+
+:author: `Patrick Kanzler <dev@pkanzler.de>`_
+:organization: `python-escpos <https://github.com/python-escpos>`_
+:copyright: Copyright (c) 2023 `python-escpos <https://github.com/python-escpos>`_
+:license: MIT
+"""
+import pathlib
+
+import appdirs
+import pytest
+
+import escpos.exceptions
+
+
+def generate_dummy_config(path, content=None):
+    """Generate a dummy config in path"""
+    dummy_config_content = content
+    if not content:
+        dummy_config_content = "printer:\n   type: Dummy\n"
+    path.write_text(dummy_config_content)
+    assert path.read_text() == dummy_config_content
+
+
+def simple_printer_test(config):
+    """Simple test for the dummy printer."""
+    p = config.printer()
+    p._raw(b"1234")
+
+    assert p.output == b"1234"
+
+
+def test_config_load_with_invalid_config_yaml(tmp_path):
+    """Test the loading of a config with a invalid config file (yaml issue)."""
+    # generate a dummy config
+    config_file = tmp_path / "config.yaml"
+    generate_dummy_config(config_file, content="}invalid}yaml}")
+
+    # test the config loading
+    from escpos import config
+
+    c = config.Config()
+    with pytest.raises(escpos.exceptions.ConfigSyntaxError):
+        c.load(config_path=config_file)
+
+
+def test_config_load_with_invalid_config_content(tmp_path):
+    """Test the loading of a config with a invalid config file (content issue)."""
+    # generate a dummy config
+    config_file = tmp_path / "config.yaml"
+    generate_dummy_config(
+        config_file, content="printer:\n   type: NoPrinterWithThatName\n"
+    )
+
+    # test the config loading
+    from escpos import config
+
+    c = config.Config()
+    with pytest.raises(escpos.exceptions.ConfigSyntaxError):
+        c.load(config_path=config_file)
+
+
+def test_config_load_with_missing_config(tmp_path):
+    """Test the loading of a config that does not exist."""
+    # test the config loading
+    from escpos import config
+
+    c = config.Config()
+    with pytest.raises(escpos.exceptions.ConfigNotFoundError):
+        c.load(config_path=tmp_path)
+
+
+@pytest.mark.skip(
+    "This test creates in the actual appdir files and is therefore skipped."
+)
+def test_config_load_from_appdir():
+    """Test the loading of a config in appdir."""
+    from escpos import config
+
+    # generate a dummy config
+    config_file = (
+        pathlib.Path(appdirs.user_config_dir(config.Config._app_name))
+        / config.Config._config_file
+    )
+
+    generate_dummy_config(config_file)
+
+    # test the config loading
+    c = config.Config()
+    c.load()
+
+    # test the resulting printer object
+    simple_printer_test(c)
+
+
+def test_config_load_with_file(tmp_path):
+    """Test the loading of a config with a config file."""
+    # generate a dummy config
+    config_file = tmp_path / "config.yaml"
+    generate_dummy_config(config_file)
+
+    # test the config loading
+    from escpos import config
+
+    c = config.Config()
+    c.load(config_path=config_file)
+
+    # test the resulting printer object
+    simple_printer_test(c)
+
+
+def test_config_load_with_path(tmp_path):
+    """Test the loading of a config with a config path."""
+    # generate a dummy config
+    config_file = tmp_path / "config.yaml"
+    generate_dummy_config(config_file)
+
+    # test the config loading
+    from escpos import config
+
+    c = config.Config()
+    c.load(config_path=tmp_path)
+
+    # test the resulting printer object
+    simple_printer_test(c)