release: v0.46.0 [skip ci]

.gitea/workflows/ci.yml

@@ -46,7 +46,7 @@ jobs:
       - name: Check unit test speed
         run: |
           . .venv/bin/activate 2>/dev/null || true
-          python3 -m devx.tools.check_test_speed --max-seconds 6 --max-single-seconds 0.5
+          python3 -m devx.tools.check_test_speed --max-seconds 8 --max-single-seconds 0.5
       - name: Documentation gate (coverage + stale refs + lint + version refs + prose)
         env:
           DEVX_DOC_COVERAGE_STRICT: "1"

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All notable changes to this project will be documented in this file.
 
+## [0.46.0] - 2026-07-14
+
+### Features
+
+- Make check_test_isolation configurable via pyproject.toml
+
 ## [0.45.1] - 2026-07-14
 
 ### Bug Fixes

README.md

@@ -16,12 +16,12 @@ quality badges.
 
 [![CI](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions/workflows/ci.yml/badge.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
 [![License: GPL-3.0](https://img.shields.io/badge/license-GPL--3.0-blue)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/src/branch/master/LICENSE)
-[![Coverage](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/coverage.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
+[![Coverage](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/coverage.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
-[![Tests](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/tests.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
+[![Tests](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/tests.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
-[![Docs](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/docs.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/wiki)
+[![Docs](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/docs.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/wiki)
-[![Code Quality](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/quality.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
+[![Code Quality](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/quality.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
-[![Version](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/version.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/releases)
+[![Version](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/version.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/releases)
-[![Python](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/python.svg)](https://www.python.org/downloads/)
+[![Python](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/python.svg)](https://www.python.org/downloads/)
 
 ## Why devx?
 
@@ -87,7 +87,7 @@ extra index and list devx in your dependencies:
 ```toml
 [project]
 dependencies = [
-    "devx>=0.45.1",
+    "devx>=0.46.0",
 ]
 
 [tool.pip]
@@ -101,8 +101,8 @@ pip install -e .
 ```
 
 > **Note:** If your project requires a specific devx version, pin it in
-> `dependencies` (for example, `"devx==0.45.1"`) or use a version constraint
+> `dependencies` (for example, `"devx==0.46.0"`) or use a version constraint
-> (for example, `"devx>=0.45.1,<0.46"`).
+> (for example, `"devx>=0.46.0,<0.47"`).
 
 ### Optional extras
 

docs/index.md

@@ -12,12 +12,12 @@ project to be reusable across all oblachno-oss repositories.
 
 [![CI](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions/workflows/ci.yml/badge.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
 [![License: GPL-3.0](https://img.shields.io/badge/license-GPL--3.0-blue)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/src/branch/master/LICENSE)
-[![Coverage](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/coverage.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
+[![Coverage](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/coverage.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
-[![Tests](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/tests.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
+[![Tests](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/tests.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
-[![Docs](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/docs.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/wiki)
+[![Docs](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/docs.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/wiki)
-[![Code Quality](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/quality.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
+[![Code Quality](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/quality.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/actions)
-[![Version](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/version.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/releases)
+[![Version](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/version.svg)](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/releases)
-[![Python](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/5a9243cc071edcccb12a47208a632e903e29adf7/python.svg)](https://www.python.org/downloads/)
+[![Python](https://git.oblachno.oblachno.fyi/oblachno-oss/devx/raw/commit/b6a7c5d7fcb500db7b56eccab165090fbe62b609/python.svg)](https://www.python.org/downloads/)
 
 ## Overview
 
@@ -74,14 +74,14 @@ Add devx to your `pyproject.toml` dependencies and configure the registry:
 ```toml
 [project]
 dependencies = [
-    "devx>=0.45.1",
+    "devx>=0.46.0",
 ]
 
 [tool.pip]
 extra-index-url = "https://git.oblachno.oblachno.fyi/api/packages/oblachno-oss/pypi/simple"
 ```
 
-Pin a specific version if needed: `"devx==0.45.1"` or `"devx>=0.45.1,<0.46"`.
+Pin a specific version if needed: `"devx==0.46.0"` or `"devx>=0.46.0,<0.47"`.
 
 ### Optional extras
 

docs/user/getting-started.md

@@ -48,12 +48,12 @@ Add devx to your `pyproject.toml`:
 ```toml
 [project]
 dependencies = [
-    "devx>=0.45.1",
+    "devx>=0.46.0",
 ]
 
 [project.optional-dependencies]
 dev = [
-    "devx>=0.45.1",
+    "devx>=0.46.0",
 ]
 ```
 

src/devx/__init__.py

@@ -1,3 +1,3 @@
 """devx — reusable development and CI/CD tools for oblachno-oss projects."""
 
-__version__ = "0.45.1"
+__version__ = "0.46.0"

src/devx/tools/check_test_isolation.py

@@ -25,6 +25,25 @@ This module is used in two ways:
    findings are reported as advisories (exit 0) since static analysis
    can't predict early exits — the runtime audit is authoritative.
 
+Project-Specific Configuration
+-------------------------------
+
+Projects can extend the built-in rule sets via ``[tool.devx.check_test_isolation]``
+in ``pyproject.toml``.  Entries are merged on top of the defaults — they
+add to (not replace) the built-in rules::
+
+    [tool.devx.check_test_isolation]
+    # Functions known to do filesystem or network I/O
+    io_functions = { "my_func" = "reads config from disk", ... }
+    # Functions known to spawn subprocesses
+    subprocess_helpers = { "my_helper" = "calls subprocess.run", ... }
+    # Transitive deps: if a helper calls these, patching any of them is safe
+    helper_internal_calls = { "my_helper" = ["subprocess", "run_cmd"], ... }
+    # I/O function internal deps: patching any of these makes the call safe
+    io_internal_calls = { "my_func" = ["open", "yaml"], ... }
+    # Heavy modules slow to import at module level in test files
+    heavy_module_imports = { "mymodule" = 150.0, ... }
+
 Patterns detected:
 
 1. **Unpatched subprocess calls** — test functions that call
@@ -60,6 +79,7 @@ from pathlib import Path
 
 import click
 
+from devx.config import _load_pyproject_devx
 from devx.i18n import _
 
 # ── Configuration ─────────────────────────────────────────────────────────────
@@ -71,7 +91,7 @@ DEFAULT_MAX_LOOP_ITERATIONS = 100
 # Maps module name → approximate import time in milliseconds.
 # NOTE: ``requests`` is excluded because it's a core devx dependency —
 # it's loaded during collection regardless of whether test files import it.
-HEAVY_MODULE_IMPORTS: dict[str, float] = {
+_DEFAULT_HEAVY_MODULE_IMPORTS: dict[str, float] = {
     "httpx": 80.0,
     "aiohttp": 120.0,
     "docker": 90.0,
@@ -96,7 +116,7 @@ HEAVY_MODULE_IMPORTS: dict[str, float] = {
 # Functions known to spawn subprocesses.  When a test calls any of these
 # without patching them, the real subprocess runs.
 # Maps function name → human-readable description.
-KNOWN_SUBPROCESS_HELPERS: dict[str, str] = {
+_DEFAULT_SUBPROCESS_HELPERS: dict[str, str] = {
     "update_doc_versions": "calls subprocess.run to run check_doc_versions --fix",
     "run_tests": "calls run_cmd to run make lint-ruff and make pytest-cov",
     "run_cmd": "calls subprocess.run for shell commands",
@@ -105,7 +125,7 @@ KNOWN_SUBPROCESS_HELPERS: dict[str, str] = {
 # Functions known to do filesystem or network I/O that should be mocked in tests.
 # Maps function name → description of what I/O it does.
 # If a test calls one of these without a corresponding @patch, it's a violation.
-KNOWN_IO_FUNCTIONS: dict[str, str] = {  # nosec B105 — descriptions, not passwords
+_DEFAULT_IO_FUNCTIONS: dict[str, str] = {  # nosec B105 — descriptions, not passwords
     "get_pat": "reads ZITADEL PAT from filesystem/env (ZitadelAuth._iter_sources)",
     "load_secrets": "reads YAML config file from disk",
     "get_customer_secret": "reads customer-specific config from disk",
@@ -124,7 +144,7 @@ KNOWN_IO_FUNCTIONS: dict[str, str] = {  # nosec B105 — descriptions, not passw
 # Transitive dependencies: if a helper calls another helper that is patched,
 # the call is safe.  Maps helper → set of function names it internally calls.
 # If ANY of these are in the test's patches, the helper call is safe.
-HELPER_INTERNAL_CALLS: dict[str, set[str]] = {
+_DEFAULT_HELPER_INTERNAL_CALLS: dict[str, set[str]] = {
     "run_tests": {"run_cmd", "subprocess"},
     "update_doc_versions": {"subprocess"},
     "run_cmd": {"subprocess"},
@@ -133,7 +153,7 @@ HELPER_INTERNAL_CALLS: dict[str, set[str]] = {
 # I/O function internal dependencies: if a test patches one of these
 # internal dependencies, the I/O function call is considered safe.
 # Maps I/O function name → set of internal function/method names it calls.
-IO_INTERNAL_CALLS: dict[str, set[str]] = {
+_DEFAULT_IO_INTERNAL_CALLS: dict[str, set[str]] = {
     "get_customer_vm_ip": {"get_tofu_output", "get_tofu_vm_ip", "subprocess"},
     "get_observability_vm_ip": {"get_tofu_output", "get_tofu_vm_ip", "subprocess"},
     "get_pat": {
@@ -150,6 +170,76 @@ IO_INTERNAL_CALLS: dict[str, set[str]] = {
     "get_customer_secret": {"load_customer_secrets", "load_vault_yaml", "load_secrets", "REPO_ROOT", "open"},
 }
 
+
+def _load_test_isolation_config() -> None:
+    """Merge project-specific rules from ``[tool.devx.check_test_isolation]``.
+
+    Reads from pyproject.toml and merges with defaults. Project-specific
+    entries are added on top of (not replacing) the built-in defaults.
+
+    Supported keys::
+
+        [tool.devx.check_test_isolation]
+        io_functions = { "my_func" = "does network I/O", ... }
+        subprocess_helpers = { "my_helper" = "calls subprocess.run", ... }
+        helper_internal_calls = { "my_helper" = ["subprocess", "run_cmd"], ... }
+        io_internal_calls = { "my_func" = ["open", "yaml"], ... }
+        heavy_module_imports = { "mymodule" = 150.0, ... }
+    """
+    devx_cfg = _load_pyproject_devx()
+    cfg_raw = devx_cfg.get("check_test_isolation", {})
+    if not isinstance(cfg_raw, dict):
+        return
+    cfg: dict[str, object] = cfg_raw  # type: ignore[assignment]
+
+    # io_functions: {name: description}
+    io_extra = cfg.get("io_functions", {})
+    if isinstance(io_extra, dict):
+        for name, desc in io_extra.items():
+            if isinstance(name, str) and isinstance(desc, str):
+                KNOWN_IO_FUNCTIONS[name] = desc
+
+    # subprocess_helpers: {name: description}
+    sp_extra = cfg.get("subprocess_helpers", {})
+    if isinstance(sp_extra, dict):
+        for name, desc in sp_extra.items():
+            if isinstance(name, str) and isinstance(desc, str):
+                KNOWN_SUBPROCESS_HELPERS[name] = desc
+
+    # helper_internal_calls: {name: [deps]}
+    hic_extra = cfg.get("helper_internal_calls", {})
+    if isinstance(hic_extra, dict):
+        for name, deps in hic_extra.items():
+            if isinstance(name, str) and isinstance(deps, list):
+                deps_set = {str(d) for d in deps if isinstance(d, str)}
+                HELPER_INTERNAL_CALLS.setdefault(name, set()).update(deps_set)
+
+    # io_internal_calls: {name: [deps]}
+    iic_extra = cfg.get("io_internal_calls", {})
+    if isinstance(iic_extra, dict):
+        for name, deps in iic_extra.items():
+            if isinstance(name, str) and isinstance(deps, list):
+                deps_set = {str(d) for d in deps if isinstance(d, str)}
+                IO_INTERNAL_CALLS.setdefault(name, set()).update(deps_set)
+
+    # heavy_module_imports: {name: ms}
+    hmi_extra = cfg.get("heavy_module_imports", {})
+    if isinstance(hmi_extra, dict):
+        for name, ms in hmi_extra.items():
+            if isinstance(name, str) and isinstance(ms, (int, float)):
+                HEAVY_MODULE_IMPORTS[name] = float(ms)
+
+
+# Active rule sets — start with defaults, merged with project config at import.
+HEAVY_MODULE_IMPORTS: dict[str, float] = dict(_DEFAULT_HEAVY_MODULE_IMPORTS)
+KNOWN_SUBPROCESS_HELPERS: dict[str, str] = dict(_DEFAULT_SUBPROCESS_HELPERS)
+KNOWN_IO_FUNCTIONS: dict[str, str] = dict(_DEFAULT_IO_FUNCTIONS)
+HELPER_INTERNAL_CALLS: dict[str, set[str]] = {k: set(v) for k, v in _DEFAULT_HELPER_INTERNAL_CALLS.items()}
+IO_INTERNAL_CALLS: dict[str, set[str]] = {k: set(v) for k, v in _DEFAULT_IO_INTERNAL_CALLS.items()}
+
+# Merge project-specific configuration from pyproject.toml
+_load_test_isolation_config()
+
 # subprocess functions that the runtime audit wraps.
 _SUBPROCESS_FUNCS = ("run", "call", "check_call", "check_output", "Popen")
 

tests/unit/test_check_test_isolation.py

@@ -8,14 +8,19 @@ import textwrap
 from pathlib import Path
 from unittest.mock import MagicMock
 
+import pytest
 from click.testing import CliRunner
 
 from devx.tools.check_test_isolation import (
+    HEAVY_MODULE_IMPORTS,
     HELPER_INTERNAL_CALLS,
+    IO_INTERNAL_CALLS,
+    KNOWN_IO_FUNCTIONS,
     KNOWN_SUBPROCESS_HELPERS,
     CallGraph,
     _extract_patch_targets,
     _is_integration_test,
+    _load_test_isolation_config,
     _SubprocessAudit,
     analyze_file,
     analyze_test_files,
@@ -1667,3 +1672,110 @@ class TestIsIntegrationTest:
         item.keywords = {}
         item.fspath = "tests/unit/test_foo.py"
         assert _is_integration_test(item) is False
+
+
+class TestLoadTestIsolationConfig:
+    """Tests for _load_test_isolation_config — project-specific rule merging."""
+
+    def test_merges_io_functions(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Project-specific io_functions are added to KNOWN_IO_FUNCTIONS."""
+        pyproject = tmp_path / "pyproject.toml"
+        pyproject.write_text(
+            '[tool.devx.check_test_isolation]\nio_functions = { "my_custom_io" = "reads from disk" }\n'
+        )
+        monkeypatch.chdir(tmp_path)
+        _load_test_isolation_config()
+        assert "my_custom_io" in KNOWN_IO_FUNCTIONS
+        assert KNOWN_IO_FUNCTIONS["my_custom_io"] == "reads from disk"
+
+    def test_merges_subprocess_helpers(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Project-specific subprocess_helpers are added."""
+        pyproject = tmp_path / "pyproject.toml"
+        pyproject.write_text(
+            '[tool.devx.check_test_isolation]\nsubprocess_helpers = { "my_sp_helper" = "calls subprocess.run" }\n'
+        )
+        monkeypatch.chdir(tmp_path)
+        _load_test_isolation_config()
+        assert "my_sp_helper" in KNOWN_SUBPROCESS_HELPERS
+
+    def test_merges_helper_internal_calls(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Project-specific helper_internal_calls are merged."""
+        pyproject = tmp_path / "pyproject.toml"
+        pyproject.write_text(
+            '[tool.devx.check_test_isolation]\nhelper_internal_calls = { "my_helper" = ["subprocess", "run_cmd"] }\n'
+        )
+        monkeypatch.chdir(tmp_path)
+        _load_test_isolation_config()
+        assert "my_helper" in HELPER_INTERNAL_CALLS
+        assert HELPER_INTERNAL_CALLS["my_helper"] == {"subprocess", "run_cmd"}
+
+    def test_merges_io_internal_calls(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Project-specific io_internal_calls are merged."""
+        pyproject = tmp_path / "pyproject.toml"
+        pyproject.write_text(
+            '[tool.devx.check_test_isolation]\nio_internal_calls = { "my_io_func" = ["open", "yaml"] }\n'
+        )
+        monkeypatch.chdir(tmp_path)
+        _load_test_isolation_config()
+        assert "my_io_func" in IO_INTERNAL_CALLS
+        assert IO_INTERNAL_CALLS["my_io_func"] == {"open", "yaml"}
+
+    def test_merges_heavy_module_imports(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Project-specific heavy_module_imports are merged."""
+        pyproject = tmp_path / "pyproject.toml"
+        pyproject.write_text('[tool.devx.check_test_isolation]\nheavy_module_imports = { "mymodule" = 150.0 }\n')
+        monkeypatch.chdir(tmp_path)
+        _load_test_isolation_config()
+        assert "mymodule" in HEAVY_MODULE_IMPORTS
+        assert HEAVY_MODULE_IMPORTS["mymodule"] == 150.0
+
+    def test_no_config_section_is_noop(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Missing [tool.devx.check_test_isolation] section is a no-op."""
+        pyproject = tmp_path / "pyproject.toml"
+        pyproject.write_text('[tool.devx]\nother_key = "value"\n')
+        monkeypatch.chdir(tmp_path)
+        before_io = dict(KNOWN_IO_FUNCTIONS)
+        _load_test_isolation_config()
+        assert before_io == KNOWN_IO_FUNCTIONS
+
+    def test_no_pyproject_is_noop(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """No pyproject.toml at all is a no-op."""
+        monkeypatch.chdir(tmp_path)
+        before = dict(KNOWN_SUBPROCESS_HELPERS)
+        _load_test_isolation_config()
+        assert before == KNOWN_SUBPROCESS_HELPERS
+
+    def test_non_dict_config_is_noop(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """A non-dict check_test_isolation section is a no-op."""
+        pyproject = tmp_path / "pyproject.toml"
+        pyproject.write_text('[tool.devx]\ncheck_test_isolation = "not_a_dict"\n')
+        monkeypatch.chdir(tmp_path)
+        before = dict(HEAVY_MODULE_IMPORTS)
+        _load_test_isolation_config()
+        assert before == HEAVY_MODULE_IMPORTS
+
+    def test_invalid_entry_types_are_skipped(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Entries with wrong types (non-str values) are silently skipped."""
+        pyproject = tmp_path / "pyproject.toml"
+        pyproject.write_text(
+            "[tool.devx.check_test_isolation]\n"
+            'io_functions = { "good_func" = "desc", "bad_func" = 123 }\n'
+            'heavy_module_imports = { "good_mod" = 100.0, "bad_mod" = "fast" }\n'
+        )
+        monkeypatch.chdir(tmp_path)
+        _load_test_isolation_config()
+        assert "good_func" in KNOWN_IO_FUNCTIONS
+        assert "bad_func" not in KNOWN_IO_FUNCTIONS
+        assert "good_mod" in HEAVY_MODULE_IMPORTS
+        assert "bad_mod" not in HEAVY_MODULE_IMPORTS
+
+    def test_extends_without_replacing_defaults(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Project config adds to defaults without removing them."""
+        pyproject = tmp_path / "pyproject.toml"
+        pyproject.write_text('[tool.devx.check_test_isolation]\nio_functions = { "project_func" = "project I/O" }\n')
+        monkeypatch.chdir(tmp_path)
+        _load_test_isolation_config()
+        # Default entries still present
+        assert "get_pat" in KNOWN_IO_FUNCTIONS
+        # Project entry added
+        assert "project_func" in KNOWN_IO_FUNCTIONS