docs: add missing tests for getting started examples (#4662)

* docs: add missing tests for getting started examples

Add test_metrics.py and test_otlpcollector.py to validate the
metrics_example.py and otlpcollector_example.py scripts.

- test_metrics.py: Validates all 7 metric types with specific expected values
- test_otlpcollector.py: Tests OTLP collector example with graceful timeout handling

Fixes #4001

* Fix lint errors

* Apply pre-commit fixes

---------

Co-authored-by: Riccardo Magliocchetti <[email protected]>

Author: sginji

docs/getting_started/tests/test_metrics.py

@@ -0,0 +1,103 @@
+# Copyright The OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import json
+import os
+import subprocess
+import sys
+import unittest
+
+
+class TestMetrics(unittest.TestCase):
+    def test_metrics(self):
+        """Test that metrics example produces expected values"""
+        # Run the metrics example
+        test_script = f"{os.path.dirname(os.path.realpath(__file__))}/../metrics_example.py"
+
+        result = subprocess.run(
+            [sys.executable, test_script],
+            capture_output=True,
+            text=True,
+            timeout=10,
+            check=True,
+        )
+
+        # Script should run successfully
+        self.assertEqual(result.returncode, 0)
+
+        # Parse the JSON output
+        output_data = json.loads(result.stdout)
+
+        # Get the metrics from the JSON structure
+        metrics = output_data["resource_metrics"][0]["scope_metrics"][0][
+            "metrics"
+        ]
+
+        # Create a lookup dict for easier testing
+        metrics_by_name = {metric["name"]: metric for metric in metrics}
+
+        # Test Counter: should be 1 (called counter.add(1))
+        counter_value = metrics_by_name["counter"]["data"]["data_points"][0][
+            "value"
+        ]
+        self.assertEqual(counter_value, 1, "Counter should have value 1")
+
+        # Test UpDownCounter: should be -4 (1 + (-5) = -4)
+        updown_value = metrics_by_name["updown_counter"]["data"][
+            "data_points"
+        ][0]["value"]
+        self.assertEqual(
+            updown_value, -4, "UpDownCounter should have value -4"
+        )
+
+        # Test Histogram: should have count=1, sum=99.9
+        histogram_data = metrics_by_name["histogram"]["data"]["data_points"][0]
+        self.assertEqual(
+            histogram_data["count"], 1, "Histogram should have count 1"
+        )
+        self.assertEqual(
+            histogram_data["sum"], 99.9, "Histogram should have sum 99.9"
+        )
+
+        # Test Gauge: should be 1 (last value set)
+        gauge_value = metrics_by_name["gauge"]["data"]["data_points"][0][
+            "value"
+        ]
+        self.assertEqual(gauge_value, 1, "Gauge should have value 1")
+
+        # Test Observable Counter: should be 1 (from callback)
+        obs_counter_value = metrics_by_name["observable_counter"]["data"][
+            "data_points"
+        ][0]["value"]
+        self.assertEqual(
+            obs_counter_value, 1, "Observable counter should have value 1"
+        )
+
+        # Test Observable UpDownCounter: should be -10 (from callback)
+        obs_updown_value = metrics_by_name["observable_updown_counter"][
+            "data"
+        ]["data_points"][0]["value"]
+        self.assertEqual(
+            obs_updown_value,
+            -10,
+            "Observable updown counter should have value -10",
+        )
+
+        # Test Observable Gauge: should be 9 (from callback)
+        obs_gauge_value = metrics_by_name["observable_gauge"]["data"][
+            "data_points"
+        ][0]["value"]
+        self.assertEqual(
+            obs_gauge_value, 9, "Observable gauge should have value 9"
+        )

docs/getting_started/tests/test_otlpcollector.py

@@ -0,0 +1,43 @@
+# Copyright The OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# oltpcollector_example.py
+import os
+import subprocess
+import sys
+import unittest
+
+
+class TestOTLPCollector(unittest.TestCase):
+    def test_otlpcollector(self):
+        """Test that OTLP collector example outputs 'Hello world!'"""
+        dirpath = os.path.dirname(os.path.realpath(__file__))
+        test_script = f"{dirpath}/../otlpcollector_example.py"
+
+        # Run the script with a short timeout since it will retry forever
+        with subprocess.Popen(
+            [sys.executable, test_script],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            text=True,
+        ) as process:
+            # Wait 2 seconds then kill it (enough time to print "Hello world!")
+            try:
+                stdout, _ = process.communicate(timeout=2)
+            except subprocess.TimeoutExpired:
+                process.kill()
+                stdout, _ = process.communicate()
+
+        # Check that it printed the expected message
+        self.assertIn("Hello world!", stdout)