### Install Dependencies with uv

Source: https://github.com/boxed/mutmut/blob/main/CONTRIBUTING.rst

Use this command to synchronize and install project dependencies using uv.

```console
uv sync
```

--------------------------------

### Install Local Mutmut for Poetry Projects

Source: https://github.com/boxed/mutmut/blob/main/CONTRIBUTING.rst

Install your local, editable version of Mutmut for projects managed with Poetry, and then install project dependencies.

```console
poetry add --group dev --editable <path_to_mutmut_codebase>
pip install -r <path_to_mutmut_codebase>/requirements.txt
```

--------------------------------

### Install and Run mutmut

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Basic commands to install the package and initiate a mutation test run.

```console
pip install mutmut
mutmut run
```

--------------------------------

### Run Mutation Testing

Source: https://github.com/boxed/mutmut/blob/main/e2e_projects/benchmark_1k/README.md

Navigate to the benchmark directory and execute the mutmut run command to start mutation testing.

```bash
cd e2e_projects/benchmark_1k
mutmut run
```

--------------------------------

### Run Linting and Formatting

Source: https://github.com/boxed/mutmut/blob/main/CONTRIBUTING.rst

Apply linting and formatting checks across all files using ruff and pre-commit. Install pre-commit hooks for automatic checks on commit.

```console
uv run pre-commit run --all-files
```

```bash
pre-commit install
```

--------------------------------

### Install Local Mutmut for Pip Projects

Source: https://github.com/boxed/mutmut/blob/main/CONTRIBUTING.rst

Install your local, editable version of Mutmut for projects managed with pip.

```console
python -m pip install --editable <path_to_mutmut_codebase>
```

--------------------------------

### Suppressing mutations across a range of lines

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Use 'no mutate start' and 'no mutate end' to suppress mutations across a specific range of lines regardless of indentation.

```python
a = mutate_this()

# pragma: no mutate start
b = skip_this()
c = skip_this_too()
# pragma: no mutate end

d = mutate_this_too()
```

--------------------------------

### Configure mutmut via setup.cfg

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Define source paths and test selection arguments in the project's setup.cfg file.

```ini
[mutmut]
source_paths=src/
pytest_add_cli_args_test_selection=tests/
```

--------------------------------

### Configure mutmut via pyproject.toml

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Define configuration settings using the tool.mutmut section in pyproject.toml.

```toml
[tool.mutmut]
source_paths = [ "src/" ]
pytest_add_cli_args_test_selection= [ "tests/" ]
```

--------------------------------

### Configure Extra Files to Copy

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Specify additional files or directories required for the test suite to run correctly.

```ini
also_copy=
    iommi/snapshots/
    conftest.py
```

--------------------------------

### Configure dependency change behavior

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Set the action to take when a watched dependency file changes.

```toml
on_dependency_change = "warn"
```

--------------------------------

### Run Benchmark Comparison

Source: https://github.com/boxed/mutmut/blob/main/e2e_projects/benchmark_1k/README.md

Execute the benchmark comparison script to test mutmut's performance across different strategies.

```bash
python run_benchmark.py
```

--------------------------------

### View Benchmark Results

Source: https://github.com/boxed/mutmut/blob/main/e2e_projects/benchmark_1k/README.md

Display the mutation testing summary results in a formatted JSON output.

```bash
cat mutants/summary.json | python -m json.tool
```

--------------------------------

### Configure Test Delay for Benchmark

Source: https://github.com/boxed/mutmut/blob/main/e2e_projects/benchmark_1k/README.md

Run the benchmark script with a specified test delay to simulate per-test runtime costs.

```bash
python run_benchmark.py --test-delay 0.01
```

--------------------------------

### Run Tests in a Container

Source: https://github.com/boxed/mutmut/blob/main/CONTRIBUTING.rst

Execute the test suite within a Linux container, as done in CI.

```bash
./scripts/run_tests.sh
```

--------------------------------

### Configure mutation timeout settings

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Adjust the timeout parameters used to kill slow mutations.

```toml
# Configure how long mutmut waits before killing a slow mutation
# Currently calculated as (duration_of_original_tests + timeout_constant) * timeout_multiplier seconds
timeout_constant = 1.0
timeout_multiplier = 15.0
```

--------------------------------

### Enable debug output

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Set to true to display detailed test output during mutation runs.

```text
debug=true
```

--------------------------------

### Run Mutants with Wildcards

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Target specific modules or functions for mutation testing using Unix-style filename patterns.

```console
mutmut run "my_module*"
mutmut run "my_module.my_function*"
```

--------------------------------

### Run Tests with pytest

Source: https://github.com/boxed/mutmut/blob/main/CONTRIBUTING.rst

Execute all project tests using pytest. For updating inline snapshots, append `--inline-snapshot=fix`.

```console
uv run pytest
```

```console
uv run pytest --inline-snapshot=fix
```

--------------------------------

### Disable setproctitle on macOS

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Configure process title settings in pyproject.toml to avoid potential segfaults on macOS.

```toml
# pyproject.toml
[tool.mutmut]
use_setproctitle = false
```

--------------------------------

### Enable coverage-based mutation

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Set this configuration to restrict mutations only to lines identified as covered by coverage.py.

```text
mutate_only_covered_lines=true
```

--------------------------------

### Configure type checker integration

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Define the command used to run type checkers like pyrefly or mypy to filter out invalid mutants.

```python
# for pyrefly
type_check_command = ['pyrefly', 'check', '--output-format=json']
# for mypy
type_check_command = ['mypy', 'your_source_dir', '--output', 'json', '--disable-error-code', 'unused-ignore']
```

--------------------------------

### Configure cache invalidation files

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Specify additional files to watch for changes using glob patterns.

```toml
cache_invalidation_files = [ "queries/*.sql", "config/*.yaml" ]
```

--------------------------------

### Exclude Files from Mutation

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Define inclusion and exclusion patterns for files during the mutation process.

```ini
only_mutate=
    src/api/*
    src/services/*
do_not_mutate=
    *__tests.py
```

--------------------------------

### Skip mutation for functions or classes

Source: https://github.com/boxed/mutmut/blob/main/docs/index.md

Place the pragma inline on the definition line to skip the entire node and its children.

```python
def complex_algorithm():  # pragma: no mutate block
    return some_complex_calculation()

class MySettings:  # pragma: no mutate block
    DEBUG = True
    MAX_RETRIES = 3
```

--------------------------------

### Skip mutation for a single line

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Use the pragma comment to prevent mutation on a specific line of code.

```python
some_code_here()  # pragma: no mutate
```

--------------------------------

### Configure cache invalidation exclusions

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Exclude specific files or directories from triggering cache invalidation.

```toml
cache_invalidation_exclude = [ "*.json", "fixtures/snapshots/*" ]
```

--------------------------------

### Exclude code via regex patterns

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Define patterns in pyproject.toml to skip mutation for specific expressions matching the provided regex.

```toml
# pyproject.toml
[tool.mutmut]
do_not_mutate_patterns = [
    # disable mutations of all logger.info/debug/... statements
    'logger\.\w+',
    # disable mutating exceptions
    'raise \w+',
]
```

--------------------------------

### Limit Stack Depth

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Restrict mutation testing relevance to tests within a specific stack depth to improve performance.

```ini
max_stack_depth=8
```

--------------------------------

### Skip mutation for function bodies

Source: https://github.com/boxed/mutmut/blob/main/docs/index.md

Place the pragma on its own line inside a function to suppress mutation of the body while keeping the definition mutable.

```python
def foo(val=1):
    # pragma: no mutate block
    x = 1
    y = complex_calculation()
    z = x + y

def bar():
    # this function is still mutated normally
    return 42
```

--------------------------------

### Skip mutation for if-branches

Source: https://github.com/boxed/mutmut/blob/main/docs/index.md

Inline the pragma on an if-statement to suppress only that branch, leaving sibling branches mutable.

```python
if error_condition:  # pragma: no mutate block
    log_error()
    send_alert()
elif other_condition:
    # still mutated -- this branch is outside the block scope
    handle_other()
else:
    # still mutated
    handle_success()
```

--------------------------------

### Modifying pytest arguments

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Configure pytest behavior by setting specific variables for CLI arguments and file copies.

```python
# for CLI args that select or deselect tests, use `pytest_add_cli_args_test_selection`
pytest_add_cli_args_test_selection = ["-m", "not fail", "-k", "test_include"]

# for other CLI args, use `pytest_add_cli_args`
pytest_add_cli_args = ["-p", "no:some_plugin"] # disable a plugin
pytest_add_cli_args = ["-o", "xfail_strict=False"] # overrides xfail_strict from your normal config

# if you want to ignore the normal pytest configuration
# you can specify a diferent pytest ini file to be used
pytest_add_cli_args = ["-c", "mutmut_pytest.ini"]
also_copy = ["mutmut_pytest.ini"]
```

--------------------------------

### Disable git change detection

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Turn off automatic git-based change detection to use the fallback list.

```toml
use_git_change_detection = false
```

--------------------------------

### Suppressing mutations with pragmas

Source: https://github.com/boxed/mutmut/blob/main/README.rst

Use the 'no mutate block' pragma to exclude entire functions, classes, or specific if-branches from mutation testing.

```python
def complex_algorithm():  # pragma: no mutate block
    return some_complex_calculation()

class MySettings:  # pragma: no mutate block
    DEBUG = True
    MAX_RETRIES = 3
```

```python
def foo(val=1):
    # pragma: no mutate block
    x = 1
    y = complex_calculation()
    z = x + y

def bar():
    # this function is still mutated normally
    return 42
```

```python
if error_condition:  # pragma: no mutate block
    log_error()
    send_alert()
elif other_condition:
    # still mutated -- this branch is outside the block scope
    handle_other()
else:
    # still mutated
    handle_success()
```

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