Unit tests (#23)

* Added unit tests and linting tools for development

* Added pre-commit config file

* Added lint github action

* Add tests and coverage comments to PRs

* Set coverage options

* Fixed yaml

* Fixed permissions

* Omit tests in coverage report

* Run linting only on PRs

tests/metric_test.py

@@ -0,0 +1,13 @@
+import unittest
+
+from qbittorrent_exporter.exporter import Metric, MetricType
+
+
+class TestMetric(unittest.TestCase):
+    def test_metric_initialization(self):
+        metric = Metric(name="test_metric", value=10)
+        self.assertEqual(metric.name, "test_metric")
+        self.assertEqual(metric.value, 10)
+        self.assertEqual(metric.labels, {})
+        self.assertEqual(metric.help_text, "")
+        self.assertEqual(metric.metric_type, MetricType.GAUGE)