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/exporter_test.py

@@ -0,0 +1,70 @@
+import unittest
+from unittest.mock import MagicMock, patch
+
+from prometheus_client.metrics_core import CounterMetricFamily, GaugeMetricFamily
+
+from qbittorrent_exporter.exporter import (
+    Metric,
+    MetricType,
+    QbittorrentMetricsCollector,
+)
+
+
+class TestQbittorrentMetricsCollector(unittest.TestCase):
+    @patch("qbittorrent_exporter.exporter.Client")
+    def setUp(self, mock_client):
+        self.mock_client = mock_client
+        self.config = {
+            "host": "localhost",
+            "port": "8080",
+            "username": "user",
+            "password": "pass",
+            "verify_webui_certificate": False,
+        }
+        self.collector = QbittorrentMetricsCollector(self.config)
+
+    def test_init(self):
+        self.assertEqual(self.collector.config, self.config)
+        self.mock_client.assert_called_once_with(
+            host=self.config["host"],
+            port=self.config["port"],
+            username=self.config["username"],
+            password=self.config["password"],
+            VERIFY_WEBUI_CERTIFICATE=self.config["verify_webui_certificate"],
+        )
+
+    def test_collect_gauge(self):
+        mock_metric = Metric(
+            name="test_gauge",
+            metric_type=MetricType.GAUGE,
+            help_text="Test Gauge",
+            labels={"label1": "value1"},
+            value=10,
+        )
+        self.collector.get_qbittorrent_metrics = MagicMock(return_value=[mock_metric])
+
+        result = next(self.collector.collect())
+
+        self.assertIsInstance(result, GaugeMetricFamily)
+        self.assertEqual(result.name, "test_gauge")
+        self.assertEqual(result.documentation, "Test Gauge")
+        self.assertEqual(result.samples[0].labels, {"label1": "value1"})
+        self.assertEqual(result.samples[0].value, 10)
+
+    def test_collect_counter(self):
+        mock_metric = Metric(
+            name="test_counter",
+            metric_type=MetricType.COUNTER,
+            help_text="Test Counter",
+            labels={"label2": "value2"},
+            value=230,
+        )
+        self.collector.get_qbittorrent_metrics = MagicMock(return_value=[mock_metric])
+
+        result = next(self.collector.collect())
+
+        self.assertIsInstance(result, CounterMetricFamily)
+        self.assertEqual(result.name, "test_counter")
+        self.assertEqual(result.documentation, "Test Counter")
+        self.assertEqual(result.samples[0].labels, {"label2": "value2"})
+        self.assertEqual(result.samples[0].value, 230)