test: add offline pytest harness (build_launch_command injection, label-merge)

image/tests/conftest.py

@@ -0,0 +1,17 @@
+"""Shared pytest setup.
+
+These suites are pure/offline — they exercise pure functions and never touch the
+Sparks, /data, or the network. We still pin the env vars the app modules expect
+(documented in docs/guides/fastapi-image.md) to tmp paths so importing them can
+never write to the container-only /data path.
+"""
+import os
+import sys
+from pathlib import Path
+
+# Let `import app...` resolve whether or not the package is pip-installed.
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+os.environ.setdefault("REDACTION_MAP_DB", "/tmp/spark_control_test_maps.db")
+os.environ.setdefault("CONNECTIVITY_LOG", "/tmp/spark_control_test_connectivity.json")
+os.environ.setdefault("MODELS_OVERRIDES", "/tmp/spark_control_test_overrides.yaml")