faster linux build

tests/conftest.py

@@ -22,8 +22,25 @@ import pytest
 
 REPO_ROOT = Path(__file__).resolve().parents[1]
 SRC_ROOT = REPO_ROOT / "src"
-if str(SRC_ROOT) not in sys.path:
-    sys.path.insert(0, str(SRC_ROOT))
+BUILD_ROOT = REPO_ROOT / "build"
+EXAMPLES_ROOT = REPO_ROOT / "examples"
+
+# Establish import precedence once, here, before any test module is imported. The
+# test modules insert the same directories, but all of those inserts are guarded
+# by `if path not in sys.path`, so once the paths are present the guards turn
+# them into no-ops and this order sticks.
+#
+# Order matters and is not incidental:
+#   * examples/ must win over build/ because `build/gui` is also a package named
+#     `gui`; with build/ first, `import gui.viewer2d` silently resolves to the
+#     build tooling and fails.
+#   * build/ must precede site-packages so `wheel`, `common` and `release` mean
+#     the repository's build tooling, not the unrelated PyPI `wheel` package.
+#   * src/ provides the checkout's `orisys`.
+# Insert in reverse priority (each insert goes to the front).
+for _path in (SRC_ROOT, BUILD_ROOT, EXAMPLES_ROOT):
+    if str(_path) not in sys.path:
+        sys.path.insert(0, str(_path))
 
 from orisys import Sensor
 from orisys import configs as orisys_configs