[tests] Build tests from the tree they run in, not the venv's editable install (#18248)

Co-authored-by: Jonathan Swoboda <154711427+swoboda1337@users.noreply.github.com>

pyproject.toml

@@ -56,6 +56,9 @@ include = ["esphome*"]
 testpaths = [
   "tests",
 ]
+# Prepend the repo root so in-process esphome imports resolve to THIS tree,
+# not wherever the venv's editable install points (e.g. another git worktree).
+pythonpath = ["."]
 addopts = [
   "--cov=esphome",
   "--cov-branch",

tests/integration/conftest.py

@@ -63,6 +63,11 @@ def _get_platformio_env(cache_dir: Path) -> dict[str, str]:
     env["PLATFORMIO_LIBDEPS_DIR"] = str(cache_dir / "libdeps")
     # Prevent cache cleaning during integration tests
     env["ESPHOME_SKIP_CLEAN_BUILD"] = "1"
+    # Compile with THIS tree's esphome sources, not wherever the venv's editable
+    # install points (which may be a different git worktree or checkout).
+    repo_root = str(Path(__file__).resolve().parent.parent.parent)
+    existing = env.get("PYTHONPATH")
+    env["PYTHONPATH"] = f"{repo_root}{os.pathsep}{existing}" if existing else repo_root
     return env
 
 
@@ -101,7 +106,7 @@ def shared_platformio_cache() -> Generator[Path]:
                 env = _get_platformio_env(cache_dir)
 
                 subprocess.run(
-                    ["esphome", "compile", str(config_path)],
+                    [sys.executable, "-m", "esphome", "compile", str(config_path)],
                     check=True,
                     cwd=init_dir,
                     env=env,
@@ -245,6 +250,8 @@ async def compile_esphome(
         for attempt in range(max_retries):
             # Compile using subprocess, inheriting stdout/stderr to show progress
             proc = await asyncio.create_subprocess_exec(
+                sys.executable,
+                "-m",
                 "esphome",
                 "compile",
                 str(config_path),