diff --git a/ARCHITECTURE.rst b/ARCHITECTURE.rst
index 8d1f04a7..e38562bc 100644
--- a/ARCHITECTURE.rst
+++ b/ARCHITECTURE.rst
@@ -11,7 +11,7 @@ Generating mutants
 
 This phase creates a ``./mutants/`` directory, which will be used by all following phases.
 
-We start by copying ``paths_to_mutate`` to ``mutants/`` and then mutate the ``*.py`` files in there. Finally, we also copy ``also_copy`` paths to ``mutants/``, including the (guessed) test directories and some project files.
+We start by copying ``source_paths`` to ``mutants/`` and then mutate the ``*.py`` files in there. Finally, we also copy ``also_copy`` paths to ``mutants/``, including the (guessed) test directories and some project files.
 
 The mutated files contains the original code and the mutants. With the ``MUTANT_UNDER_TEST`` environment variable, we can specify (among other things) which mutant should be enabled. If a mutant is not enabled, it will run the original code.
 
diff --git a/README.rst b/README.rst
index e4de28ee..b226758c 100644
--- a/README.rst
+++ b/README.rst
@@ -88,7 +88,7 @@ In `setup.cfg` in the root of your project you can configure mutmut if you need
 .. code-block:: ini
 
     [mutmut]
-    paths_to_mutate=src/
+    source_paths=src/
     pytest_add_cli_args_test_selection=tests/
 
 If you use `pyproject.toml`, you must specify the paths as array in a `tool.mutmut` section:
@@ -96,7 +96,7 @@ If you use `pyproject.toml`, you must specify the paths as array in a `tool.mutm
 .. code-block:: toml
 
     [tool.mutmut]
-    paths_to_mutate = [ "src/" ]
+    source_paths = [ "src/" ]
     pytest_add_cli_args_test_selection= [ "tests/" ]
 
 See below for more options for configuring mutmut.
@@ -143,10 +143,14 @@ caught.
 Exclude files from mutation
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+By default mutmut mutates all python files in `source_paths`.
 You can exclude files from mutation in `setup.cfg`:
 
 .. code-block::
 
+    only_mutate=
+        src/api/*
+        src/services/*
     do_not_mutate=
         *__tests.py
 
diff --git a/e2e_projects/config/config_pkg/logic/__init__.py b/e2e_projects/config/config_pkg/logic/__init__.py
new file mode 100644
index 00000000..74b0dc93
--- /dev/null
+++ b/e2e_projects/config/config_pkg/logic/__init__.py
@@ -0,0 +1,2 @@
+def hello() -> str:
+    return "Hello from config!"
diff --git a/e2e_projects/config/config_pkg/ignore_me.py b/e2e_projects/config/config_pkg/logic/ignore_me.py
similarity index 100%
rename from e2e_projects/config/config_pkg/ignore_me.py
rename to e2e_projects/config/config_pkg/logic/ignore_me.py
diff --git a/e2e_projects/config/config_pkg/math.py b/e2e_projects/config/config_pkg/logic/math.py
similarity index 100%
rename from e2e_projects/config/config_pkg/math.py
rename to e2e_projects/config/config_pkg/logic/math.py
diff --git a/e2e_projects/config/config_pkg/utils/__init__.py b/e2e_projects/config/config_pkg/utils/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/e2e_projects/config/config_pkg/utils/utils.py b/e2e_projects/config/config_pkg/utils/utils.py
new file mode 100644
index 00000000..69b940ac
--- /dev/null
+++ b/e2e_projects/config/config_pkg/utils/utils.py
@@ -0,0 +1,2 @@
+def util_that_should_NOT_be_mutated():
+    return 1 + 2 + 3 + 4 + 5 - 7 - 8
diff --git a/e2e_projects/config/pyproject.toml b/e2e_projects/config/pyproject.toml
index 923268da..8409dc9f 100644
--- a/e2e_projects/config/pyproject.toml
+++ b/e2e_projects/config/pyproject.toml
@@ -24,15 +24,15 @@ dev = [
 
 [tool.mutmut]
 debug = true
-paths_to_mutate = [ "config_pkg/" ]
+source_paths = [ "config_pkg/" ]
+only_mutate = [ "config_pkg/logic/*" ]
 do_not_mutate = [ "*ignore*" ]
 also_copy = [ "data" ]
 max_stack_depth=8 # Includes frames by mutmut, see https://github.com/boxed/mutmut/issues/378
-tests_dir = [ "tests/main/" ]
 # verify that we can override options with pytest_add_cli_args
 pytest_add_cli_args = ["-o", "xfail_strict=False"]
 # verify test exclusion (-m 'not fail') and test inclusion (-k=test_include)
-pytest_add_cli_args_test_selection = [ "-m", "not fail", "-k=test_include"]
+pytest_add_cli_args_test_selection = [ "-m", "not fail", "-k=test_include", "tests/main/"]
 
 [tool.pytest.ini_options]
 xfail_strict = true
diff --git a/e2e_projects/config/tests/ignored/test_ignored.py b/e2e_projects/config/tests/ignored/test_ignored.py
index 8a5f51ee..8008e2c4 100644
--- a/e2e_projects/config/tests/ignored/test_ignored.py
+++ b/e2e_projects/config/tests/ignored/test_ignored.py
@@ -1,5 +1,5 @@
-from config_pkg.math import func_with_no_tests
+from config_pkg.logic.math import func_with_no_tests
 
-# ignored, because tests_dir specifies only the main directory
+# ignored, because pytest_add_cli_args_test_selection specifies only the main directory
 def test_include_func_with_no_tests():
     assert func_with_no_tests() == 420
diff --git a/e2e_projects/config/tests/main/test_main.py b/e2e_projects/config/tests/main/test_main.py
index 15500b61..018a9ea0 100644
--- a/e2e_projects/config/tests/main/test_main.py
+++ b/e2e_projects/config/tests/main/test_main.py
@@ -1,9 +1,10 @@
 import json
 import pytest
 from pathlib import Path
-from config_pkg import hello
-from config_pkg.math import add, call_depth_two
-from config_pkg.ignore_me import this_function_shall_NOT_be_mutated
+from config_pkg.logic import hello
+from config_pkg.logic.math import add, call_depth_two
+from config_pkg.logic.ignore_me import this_function_shall_NOT_be_mutated
+from config_pkg.utils.utils import util_that_should_NOT_be_mutated
 
 def test_include_hello():
     assert hello() == "Hello from config!"
@@ -14,6 +15,9 @@ def test_include_add():
 def test_include_non_mutated_function():
     assert this_function_shall_NOT_be_mutated() == 3
 
+def test_include_non_mutated_util():
+    assert util_that_should_NOT_be_mutated() == 0
+
 def test_include_max_stack_depth():
     # This test should only cover functions up to some depth
     # For more context, see https://github.com/boxed/mutmut/issues/378
diff --git a/e2e_projects/mutate_only_covered_lines/pyproject.toml b/e2e_projects/mutate_only_covered_lines/pyproject.toml
index e51233f0..0d1d866c 100644
--- a/e2e_projects/mutate_only_covered_lines/pyproject.toml
+++ b/e2e_projects/mutate_only_covered_lines/pyproject.toml
@@ -24,9 +24,9 @@ omit = [
 [tool.mutmut]
 debug = true
 mutate_only_covered_lines = true
-tests_dir = [ "tests/main/" ]
+pytest_add_cli_args_test_selection = [ "tests/main/" ]
 do_not_mutate = [ "*ignore*" ]
-# do not add paths_to_mutate because we want to test src guessing
+# do not add source_paths because we want to test src guessing
 
 [tool.pytest.ini_options]
 asyncio_default_fixture_loop_scope = "function"
diff --git a/e2e_projects/mutate_only_covered_lines/tests/other/test_that_should_not_be_included.py b/e2e_projects/mutate_only_covered_lines/tests/other/test_that_should_not_be_included.py
index 0e697978..5b00ba66 100644
--- a/e2e_projects/mutate_only_covered_lines/tests/other/test_that_should_not_be_included.py
+++ b/e2e_projects/mutate_only_covered_lines/tests/other/test_that_should_not_be_included.py
@@ -1,6 +1,6 @@
 from mutate_only_covered_lines import hello_mutate_only_covered_lines
 
-"""This test should be ignored, because of the tests_dir config."""
+"""This test should be ignored, because of the pytest_add_cli_args_test_selection config."""
 
 def test_mutate_only_covered_lines():
     assert hello_mutate_only_covered_lines(False) == "Hello from mutate_only_covered_lines! (false)"
diff --git a/src/mutmut/__main__.py b/src/mutmut/__main__.py
index 8c6f1f04..26261ec4 100644
--- a/src/mutmut/__main__.py
+++ b/src/mutmut/__main__.py
@@ -133,7 +133,7 @@ def record_trampoline_hit(name: str) -> None:
 
 
 def walk_all_files() -> Iterator[tuple[str, str]]:
-    for path in Config.get().paths_to_mutate:
+    for path in Config.get().source_paths:
         if not isdir(path):
             if isfile(path):
                 yield "", str(path)
@@ -149,6 +149,13 @@ def walk_source_files() -> Iterator[Path]:
             yield Path(root) / filename
 
 
+def walk_mutatable_files() -> Iterator[Path]:
+    config = Config.get()
+    for path in walk_source_files():
+        if config.should_mutate(path):
+            yield path
+
+
 class MutmutProgrammaticFailException(Exception):
     pass
 
@@ -228,11 +235,11 @@ def create_file_mutants(path: Path) -> FileMutationResult:
         output_path = Path("mutants") / path
         makedirs(output_path.parent, exist_ok=True)
 
-        if Config.get().should_ignore_for_mutation(path):
+        if Config.get().should_mutate(path):
+            return create_mutants_for_file(path, output_path)
+        else:
             shutil.copy(path, output_path)
             return FileMutationResult(ignored=True)
-        else:
-            return create_mutants_for_file(path, output_path)
     except Exception as e:
         return FileMutationResult(error=e)
 
@@ -388,10 +395,6 @@ def __init__(self) -> None:
         self._pytest_add_cli_args: list[str] = Config.get().pytest_add_cli_args
         self._pytest_add_cli_args_test_selection: list[str] = Config.get().pytest_add_cli_args_test_selection
 
-        # tests_dir is a special case of a test selection option,
-        # so also use pytest_add_cli_args_test_selection for the implementation
-        self._pytest_add_cli_args_test_selection += Config.get().tests_dir
-
     # noinspection PyMethodMayBeStatic
     def execute_pytest(self, params: list[str], **kwargs: Any) -> int:
         import pytest
@@ -463,7 +466,6 @@ def pytest_deselected(self, items: Any) -> None:
 
         collector = TestsCollector()
 
-        tests_dir = Config.get().tests_dir
         pytest_args = ["-x", "-q", "--collect-only"] + self._pytest_add_cli_args_test_selection
 
         with change_cwd("mutants"):
@@ -828,10 +830,7 @@ def export_cicd_stats() -> None:
 
     source_file_mutation_data_by_path: dict[str, SourceFileMutationData] = {}
 
-    for path in walk_source_files():
-        if Config.get().should_ignore_for_mutation(path):
-            continue
-
+    for path in walk_mutatable_files():
         meta_path = Path("mutants") / (str(path) + ".meta")
         if not meta_path.exists():
             continue
@@ -859,9 +858,7 @@ def collect_source_file_mutation_data(
 ]:
     source_file_mutation_data_by_path: dict[str, SourceFileMutationData] = {}
 
-    for path in walk_source_files():
-        if Config.get().should_ignore_for_mutation(path):
-            continue
+    for path in walk_mutatable_files():
         assert str(path) not in source_file_mutation_data_by_path
         m = SourceFileMutationData(path=path)
         m.load()
@@ -1060,7 +1057,9 @@ def read_one_child_exit_status() -> None:
                 if not sorted_tests:
                     os._exit(33)
 
-                cpu_time_limit_s = ceil((estimated_time_of_tests + config.timeout_constant) * config.timeout_multiplier * 2 + process_time())
+                cpu_time_limit_s = ceil(
+                    (estimated_time_of_tests + config.timeout_constant) * config.timeout_multiplier * 2 + process_time()
+                )
                 # signal SIGXCPU after <cpu_time_limit>. One second later signal SIGKILL if it is still running
                 resource.setrlimit(resource.RLIMIT_CPU, (cpu_time_limit_s, cpu_time_limit_s + 1))
 
@@ -1133,9 +1132,7 @@ def tests_for_mutant_names(mutant_names: tuple[str, ...] | list[str]) -> set[str
 @click.option("--all", default=False)
 def results(all: bool) -> None:
     Config.ensure_loaded()
-    for path in walk_source_files():
-        if not str(path).endswith(".py"):
-            continue
+    for path in walk_mutatable_files():
         m = SourceFileMutationData(path=path)
         m.load()
         for k, v in m.exit_code_by_key.items():
@@ -1188,10 +1185,7 @@ def read_mutant_function(module: cst.Module, mutant_name: str) -> cst.FunctionDe
 
 
 def find_mutant(mutant_name: str) -> SourceFileMutationData:
-    for path in walk_source_files():
-        if Config.get().should_ignore_for_mutation(path):
-            continue
-
+    for path in walk_mutatable_files():
         m = SourceFileMutationData(path=path)
         m.load()
         if mutant_name in m.exit_code_by_key:
@@ -1334,9 +1328,7 @@ def read_data(self) -> None:
             self.source_file_mutation_data_and_stat_by_path = {}
             self.path_by_name: dict[str, Path] = {}
 
-            for p in walk_source_files():
-                if Config.get().should_ignore_for_mutation(p):
-                    continue
+            for p in walk_mutatable_files():
                 source_file_mutation_data = SourceFileMutationData(path=p)
                 source_file_mutation_data.load()
                 stat = collect_stat(source_file_mutation_data)
diff --git a/src/mutmut/configuration.py b/src/mutmut/configuration.py
index 59f62d3c..d3a8ef01 100644
--- a/src/mutmut/configuration.py
+++ b/src/mutmut/configuration.py
@@ -4,6 +4,7 @@
 import os
 import platform
 import sys
+import warnings
 from collections.abc import Callable
 from configparser import ConfigParser
 from configparser import NoOptionError
@@ -64,7 +65,7 @@ def setup_cfg_conf(key: str, default: Any) -> Any:
     return setup_cfg_conf
 
 
-def _guess_paths_to_mutate() -> list[str]:
+def _guess_source_paths() -> list[str]:
     """Guess the path to source code to mutate
 
     :rtype: str
@@ -88,15 +89,38 @@ def _guess_paths_to_mutate() -> list[str]:
         return [this_dir + ".py"]
     raise FileNotFoundError(
         "Could not figure out where the code to mutate is. "
-        'Please specify it by adding "paths_to_mutate=code_dir" in setup.cfg to the [mutmut] section.'
+        'Please specify it by adding "source_paths=code_dir" in setup.cfg to the [mutmut] section.'
     )
 
 
 def _load_config() -> Config:
     s = _config_reader()
 
+    paths_to_mutate = [Path(path) for path in s("paths_to_mutate", [])]
+    if paths_to_mutate:
+        warnings.warn("The config paths_to_mutate is deprecated. Please rename it to source_paths")
+    source_paths = [Path(path) for path in s("source_paths", [])]
+    source_paths = source_paths or paths_to_mutate or [Path(path) for path in _guess_source_paths()]
+
+    tests_dir = s("tests_dir", [])
+    if tests_dir:
+        warnings.warn(
+            "The config tests_dir is deprecated. Please add the path to pytest_add_cli_args_test_selection instead"
+        )
+    pytest_add_cli_args_test_selection = s("pytest_add_cli_args_test_selection", []) + tests_dir
+
+    only_mutate = s("only_mutate", [])
+    do_not_mutate = s("do_not_mutate", [])
+    # only patterns for python files are valid: must end with ".py" or "*"
+    invalid_patterns = [p for p in only_mutate + do_not_mutate if not (p.endswith("*") or p.endswith(".py"))]
+    if invalid_patterns:
+        warnings.warn(
+            f'The configs only_mutate and do_not_mutate expect glob patterns like "src/api/*" or "src/main.py". Following patterns are likely invalid: {invalid_patterns}'
+        )
+
     return Config(
-        do_not_mutate=s("do_not_mutate", []),
+        only_mutate=only_mutate,
+        do_not_mutate=do_not_mutate,
         also_copy=[Path(y) for y in s("also_copy", [])]
         + [
             Path("tests/"),
@@ -108,10 +132,9 @@ def _load_config() -> Config:
         max_stack_depth=s("max_stack_depth", -1),
         debug=s("debug", False),
         mutate_only_covered_lines=s("mutate_only_covered_lines", False),
-        paths_to_mutate=[Path(y) for y in s("paths_to_mutate", [])] or [Path(p) for p in _guess_paths_to_mutate()],
-        tests_dir=s("tests_dir", []),
+        source_paths=source_paths,
         pytest_add_cli_args=s("pytest_add_cli_args", []),
-        pytest_add_cli_args_test_selection=s("pytest_add_cli_args_test_selection", []),
+        pytest_add_cli_args_test_selection=pytest_add_cli_args_test_selection,
         timeout_multiplier=s("timeout_multiplier", 15.0),
         timeout_constant=s("timeout_constant", 1.0),
         type_check_command=s("type_check_command", []),
@@ -127,20 +150,34 @@ def _load_config() -> Config:
 @dataclass
 class Config:
     also_copy: list[Path]
+    only_mutate: list[str]
     do_not_mutate: list[str]
     max_stack_depth: int
     debug: bool
-    paths_to_mutate: list[Path]
+    source_paths: list[Path]
     pytest_add_cli_args: list[str]
     pytest_add_cli_args_test_selection: list[str]
-    tests_dir: list[str]
     mutate_only_covered_lines: bool
     timeout_multiplier: float
     timeout_constant: float
     type_check_command: list[str]
     use_setproctitle: bool
 
-    def should_ignore_for_mutation(self, path: Path | str) -> bool:
+    def should_mutate(self, path: Path | str) -> bool:
+        return self._should_include_for_mutation(path) and not self._should_ignore_for_mutation(path)
+
+    def _should_include_for_mutation(self, path: Path | str) -> bool:
+        if not self.only_mutate:
+            return True
+        path_str = str(path)
+        if not path_str.endswith(".py"):
+            return True
+        for p in self.only_mutate:
+            if fnmatch.fnmatch(path_str, p):
+                return True
+        return False
+
+    def _should_ignore_for_mutation(self, path: Path | str) -> bool:
         path_str = str(path)
         if not path_str.endswith(".py"):
             return True
diff --git a/tests/e2e/e2e_utils.py b/tests/e2e/e2e_utils.py
index c7a6ae71..1b7ca2d4 100644
--- a/tests/e2e/e2e_utils.py
+++ b/tests/e2e/e2e_utils.py
@@ -30,7 +30,7 @@ def read_all_stats_for_project(project_path: Path) -> dict[str, dict]:
 
         stats = {}
         for p in walk_source_files():
-            if Config.get().should_ignore_for_mutation(p):
+            if not Config.get().should_mutate(p):
                 continue
             data = SourceFileMutationData(path=p)
             data.load()
diff --git a/tests/e2e/test_e2e_config.py b/tests/e2e/test_e2e_config.py
index 84b712b2..8e383e22 100644
--- a/tests/e2e/test_e2e_config.py
+++ b/tests/e2e/test_e2e_config.py
@@ -6,21 +6,21 @@
 def test_config_result_snapshot():
     assert run_mutmut_on_project("config") == snapshot(
         {
-            "mutants/config_pkg/__init__.py.meta": {
-                "config_pkg.x_hello__mutmut_1": 1,
-                "config_pkg.x_hello__mutmut_2": 1,
-                "config_pkg.x_hello__mutmut_3": 1,
+            "mutants/config_pkg/logic/__init__.py.meta": {
+                "config_pkg.logic.x_hello__mutmut_1": 1,
+                "config_pkg.logic.x_hello__mutmut_2": 1,
+                "config_pkg.logic.x_hello__mutmut_3": 1,
             },
-            "mutants/config_pkg/math.py.meta": {
-                "config_pkg.math.x_add__mutmut_1": 0,
-                "config_pkg.math.x_call_depth_two__mutmut_1": 1,
-                "config_pkg.math.x_call_depth_two__mutmut_2": 1,
-                "config_pkg.math.x_call_depth_three__mutmut_1": 1,
-                "config_pkg.math.x_call_depth_three__mutmut_2": 1,
-                "config_pkg.math.x_call_depth_four__mutmut_1": 33,
-                "config_pkg.math.x_call_depth_four__mutmut_2": 33,
-                "config_pkg.math.x_call_depth_five__mutmut_1": 33,
-                "config_pkg.math.x_func_with_no_tests__mutmut_1": 33,
+            "mutants/config_pkg/logic/math.py.meta": {
+                "config_pkg.logic.math.x_add__mutmut_1": 0,
+                "config_pkg.logic.math.x_call_depth_two__mutmut_1": 1,
+                "config_pkg.logic.math.x_call_depth_two__mutmut_2": 1,
+                "config_pkg.logic.math.x_call_depth_three__mutmut_1": 1,
+                "config_pkg.logic.math.x_call_depth_three__mutmut_2": 1,
+                "config_pkg.logic.math.x_call_depth_four__mutmut_1": 33,
+                "config_pkg.logic.math.x_call_depth_four__mutmut_2": 33,
+                "config_pkg.logic.math.x_call_depth_five__mutmut_1": 33,
+                "config_pkg.logic.math.x_func_with_no_tests__mutmut_1": 33,
             },
         }
     )
diff --git a/tests/test_configuration.py b/tests/test_configuration.py
index 445ba5bc..e8de4c54 100644
--- a/tests/test_configuration.py
+++ b/tests/test_configuration.py
@@ -4,7 +4,7 @@
 
 from mutmut.configuration import Config
 from mutmut.configuration import _config_reader
-from mutmut.configuration import _guess_paths_to_mutate
+from mutmut.configuration import _guess_source_paths
 from mutmut.configuration import _load_config
 
 
@@ -52,103 +52,90 @@ def test_ensure_loaded_is_idempotent(self, in_tmp_dir: Path):
         assert config1 is config2
 
 
-class TestShouldIgnoreForMutation:
-    def test_ignores_non_python_files(self):
-        config = Config(
+class TestShouldMutateFile:
+    @staticmethod
+    def _get_config(only_mutate: list[str], do_not_mutate: list[str]) -> Config:
+        # only the "only_mutate" and "do_not_mutate" configs are important for these tests
+        return Config(
+            only_mutate=only_mutate,
+            do_not_mutate=do_not_mutate,
             also_copy=[],
-            do_not_mutate=[],
             max_stack_depth=-1,
             debug=False,
-            paths_to_mutate=[],
+            source_paths=[],
             pytest_add_cli_args=[],
             pytest_add_cli_args_test_selection=[],
-            tests_dir=[],
             mutate_only_covered_lines=False,
             timeout_multiplier=15.0,
             timeout_constant=1.0,
             type_check_command=[],
             use_setproctitle=False,
         )
-        assert config.should_ignore_for_mutation("foo.txt") is True
-        assert config.should_ignore_for_mutation("foo.js") is True
-        assert config.should_ignore_for_mutation("foo") is True
 
-    def test_does_not_ignore_python_files(self):
-        config = Config(
-            also_copy=[],
+    def test_ignores_non_python_files(self):
+        config = self._get_config(
+            only_mutate=[],
             do_not_mutate=[],
-            max_stack_depth=-1,
-            debug=False,
-            paths_to_mutate=[],
-            pytest_add_cli_args=[],
-            pytest_add_cli_args_test_selection=[],
-            tests_dir=[],
-            mutate_only_covered_lines=False,
-            timeout_multiplier=15.0,
-            timeout_constant=1.0,
-            type_check_command=[],
-            use_setproctitle=False,
         )
-        assert config.should_ignore_for_mutation("foo.py") is False
-        assert config.should_ignore_for_mutation("src/foo.py") is False
+        assert config.should_mutate("foo.txt") is False
+        assert config.should_mutate("foo.js") is False
+        assert config.should_mutate("foo") is False
+
+    def test_includes_python_files(self):
+        config = self._get_config(
+            only_mutate=[],
+            do_not_mutate=[],
+        )
+        assert config.should_mutate("foo.py") is True
+        assert config.should_mutate("src/foo.py") is True
 
     def test_respects_do_not_mutate_exact_match(self):
-        config = Config(
-            also_copy=[],
+        config = self._get_config(
+            only_mutate=[],
             do_not_mutate=["foo.py"],
-            max_stack_depth=-1,
-            debug=False,
-            paths_to_mutate=[],
-            pytest_add_cli_args=[],
-            pytest_add_cli_args_test_selection=[],
-            tests_dir=[],
-            mutate_only_covered_lines=False,
-            timeout_multiplier=15.0,
-            timeout_constant=1.0,
-            type_check_command=[],
-            use_setproctitle=False,
         )
-        assert config.should_ignore_for_mutation("foo.py") is True
-        assert config.should_ignore_for_mutation("bar.py") is False
+        assert config.should_mutate("foo.py") is False
+        assert config.should_mutate("bar.py") is True
 
     def test_respects_do_not_mutate_glob_pattern(self):
-        config = Config(
-            also_copy=[],
+        config = self._get_config(
+            only_mutate=[],
             do_not_mutate=["**/test_*.py", "src/ignore_*.py"],
-            max_stack_depth=-1,
-            debug=False,
-            paths_to_mutate=[],
-            pytest_add_cli_args=[],
-            pytest_add_cli_args_test_selection=[],
-            tests_dir=[],
-            mutate_only_covered_lines=False,
-            timeout_multiplier=15.0,
-            timeout_constant=1.0,
-            type_check_command=[],
-            use_setproctitle=False,
         )
-        assert config.should_ignore_for_mutation("tests/test_foo.py") is True
-        assert config.should_ignore_for_mutation("src/ignore_me.py") is True
-        assert config.should_ignore_for_mutation("src/keep_me.py") is False
+        assert config.should_mutate("tests/test_foo.py") is False
+        assert config.should_mutate("src/ignore_me.py") is False
+        assert config.should_mutate("src/keep_me.py") is True
+
+    def test_respects_only_mutate(self):
+        config = self._get_config(
+            # without a glob, the `src/` is pointless
+            only_mutate=["src/", "foo/*"],
+            do_not_mutate=[],
+        )
+        assert config.should_mutate("tests/test_foo.py") is False
+        assert config.should_mutate("src/main.py") is False
+        assert config.should_mutate("foo/main.py") is True
+        assert config.should_mutate("foo/nested/main.py") is True
+
+    def test_respects_only_mutate_with_do_not_mutate(self):
+        config = self._get_config(
+            only_mutate=["src/api/*"],
+            do_not_mutate=["src/api/models/*"],
+        )
+        # matched by only_mutate
+        assert config.should_mutate("src/api/endpoints/user.py") is True
+        # matched by only_mutate but excluded by do_not_mutate
+        assert config.should_mutate("src/api/models/user.py") is False
+        # not matched by only_mutate
+        assert config.should_mutate("src/services/user.py") is False
 
     def test_accepts_path_objects(self):
-        config = Config(
-            also_copy=[],
+        config = self._get_config(
+            only_mutate=[],
             do_not_mutate=["foo.py"],
-            max_stack_depth=-1,
-            debug=False,
-            paths_to_mutate=[],
-            pytest_add_cli_args=[],
-            pytest_add_cli_args_test_selection=[],
-            tests_dir=[],
-            mutate_only_covered_lines=False,
-            timeout_multiplier=15.0,
-            timeout_constant=1.0,
-            type_check_command=[],
-            use_setproctitle=False,
         )
-        assert config.should_ignore_for_mutation(Path("foo.py")) is True
-        assert config.should_ignore_for_mutation(Path("bar.py")) is False
+        assert config.should_mutate(Path("foo.py")) is False
+        assert config.should_mutate(Path("bar.py")) is True
 
 
 class TestConfigReaderPyprojectToml:
@@ -157,13 +144,13 @@ def test_reads_from_pyproject_toml(self, in_tmp_dir: Path):
 [tool.mutmut]
 debug = true
 max_stack_depth = 10
-paths_to_mutate = ["src", "lib"]
+source_paths = ["src", "lib"]
 do_not_mutate = ["**/migrations/*"]
 """)
         reader = _config_reader()
         assert reader("debug", False) is True
         assert reader("max_stack_depth", -1) == 10
-        assert reader("paths_to_mutate", []) == ["src", "lib"]
+        assert reader("source_paths", []) == ["src", "lib"]
         assert reader("do_not_mutate", []) == ["**/migrations/*"]
 
     def test_returns_default_for_missing_key(self, in_tmp_dir: Path):
@@ -191,12 +178,12 @@ def test_reads_from_setup_cfg(self, in_tmp_dir: Path):
 [mutmut]
 debug = true
 max_stack_depth = 5
-paths_to_mutate = src
+source_paths = src
 """)
         reader = _config_reader()
         assert reader("debug", False) is True
         assert reader("max_stack_depth", -1) == 5
-        assert reader("paths_to_mutate", []) == ["src"]
+        assert reader("source_paths", []) == ["src"]
 
     def test_parses_multiline_list(self, in_tmp_dir: Path):
         (in_tmp_dir / "setup.cfg").write_text("""
@@ -277,31 +264,31 @@ def test_pyproject_toml_takes_precedence(self, in_tmp_dir: Path):
 class TestGuessPathsToMutate:
     def test_guesses_lib_directory(self, in_tmp_dir: Path):
         (in_tmp_dir / "lib").mkdir()
-        assert _guess_paths_to_mutate() == ["lib"]
+        assert _guess_source_paths() == ["lib"]
 
     def test_guesses_src_directory(self, in_tmp_dir: Path):
         (in_tmp_dir / "src").mkdir()
-        assert _guess_paths_to_mutate() == ["src"]
+        assert _guess_source_paths() == ["src"]
 
     def test_prefers_lib_over_src(self, in_tmp_dir: Path):
         (in_tmp_dir / "lib").mkdir()
         (in_tmp_dir / "src").mkdir()
-        assert _guess_paths_to_mutate() == ["lib"]
+        assert _guess_source_paths() == ["lib"]
 
     def test_guesses_directory_matching_cwd_name(self, in_tmp_dir: Path):
         # tmp_path has a random name, create a subdir matching it
         dir_name = in_tmp_dir.name
         (in_tmp_dir / dir_name).mkdir()
-        assert _guess_paths_to_mutate() == [dir_name]
+        assert _guess_source_paths() == [dir_name]
 
     def test_guesses_py_file_matching_cwd_name(self, in_tmp_dir: Path):
         dir_name = in_tmp_dir.name
         (in_tmp_dir / f"{dir_name}.py").touch()
-        assert _guess_paths_to_mutate() == [f"{dir_name}.py"]
+        assert _guess_source_paths() == [f"{dir_name}.py"]
 
     def test_raises_when_cannot_guess(self, in_tmp_dir: Path):
         with pytest.raises(FileNotFoundError, match="Could not figure out"):
-            _guess_paths_to_mutate()
+            _guess_source_paths()
 
 
 class TestLoadConfig:
@@ -310,9 +297,9 @@ def test_loads_all_config_values(self, in_tmp_dir: Path):
 [tool.mutmut]
 debug = true
 max_stack_depth = 10
-paths_to_mutate = ["src"]
+source_paths = ["src"]
+only_mutate=["**/foo.py"]
 do_not_mutate = ["**/test_*.py"]
-tests_dir = ["tests/unit"]
 pytest_add_cli_args = ["-x", "--tb=short"]
 pytest_add_cli_args_test_selection = ["--no-header"]
 also_copy = ["fixtures"]
@@ -327,9 +314,9 @@ def test_loads_all_config_values(self, in_tmp_dir: Path):
 
         assert config.debug is True
         assert config.max_stack_depth == 10
-        assert config.paths_to_mutate == [Path("src")]
+        assert config.source_paths == [Path("src")]
+        assert config.only_mutate == ["**/foo.py"]
         assert config.do_not_mutate == ["**/test_*.py"]
-        assert config.tests_dir == ["tests/unit"]
         assert config.pytest_add_cli_args == ["-x", "--tb=short"]
         assert config.pytest_add_cli_args_test_selection == ["--no-header"]
         assert Path("fixtures") in config.also_copy
@@ -345,7 +332,8 @@ def test_uses_defaults_when_no_config(self, in_tmp_dir: Path):
 
         assert config.debug is False
         assert config.max_stack_depth == -1
-        assert config.paths_to_mutate == [Path("src")]
+        assert config.source_paths == [Path("src")]
+        assert config.only_mutate == []
         assert config.do_not_mutate == []
         assert config.mutate_only_covered_lines is False
         assert config.timeout_multiplier == 15.0
diff --git a/tests/test_generation_error_handling.py b/tests/test_generation_error_handling.py
index f556e392..ad3e087f 100644
--- a/tests/test_generation_error_handling.py
+++ b/tests/test_generation_error_handling.py
@@ -25,7 +25,7 @@ def test_mutant_generation_raises_exception_on_invalid_syntax(monkeypatch):
         source_dir / "invalid_syntax.py",
     ]
     monkeypatch.setattr(mutmut.__main__, "walk_source_files", lambda: source_files)
-    monkeypatch.setattr(Config.get(), "should_ignore_for_mutation", lambda _path: False)
+    monkeypatch.setattr(Config.get(), "should_mutate", lambda _path: True)
 
     # should raise an exception, because we copy the invalid_syntax.py file and then verify
     # if it is valid syntax