OeditusCredo.Check.Refactoring.ChangeRiskAntiPatterns (OeditusCredo v0.8.0)

Basics

This check has a base priority of low and works with any version of Elixir.

Explanation

Functions that are both complex and under-tested are the riskiest to change. The CRAP (Change Risk Anti-Patterns) score surfaces them by combining cyclomatic complexity with test coverage:

CRAP = complexity^2 * (1 - coverage/100)^3 + complexity

IMPORTANT: this check needs persisted coverage data and must be run AFTER generating it:

mix test --cover --export-coverage default
mix credo

Plain mix test --cover does not leave an importable coverage file. When no coverage data is available the check does nothing by default (set require_coverage: true to flag that situation instead).

A high score is a prompt to investigate: add meaningful tests, simplify the function, or write characterization tests before refactoring risky legacy code. Cyclomatic complexity is only a proxy for path/test burden; it does not measure naming, cohesion, or whether tests assert anything meaningful.

Check-Specific Parameters

Use the following parameters to configure this check:

:max_score

The maximum CRAP score a function may have before it is reported.

This parameter defaults to nil.

:coverdata

Path to the persisted coverage file, relative to the project root (default cover/default.coverdata).

This parameter defaults to nil.

:exclude_test_files

Set to false to also score test files (default: true).

This parameter defaults to nil.

:require_coverage

When true, report an issue if coverage data is missing instead of silently skipping (default: false).

This parameter defaults to nil.

:coverage

Advanced/testing: an explicit %{{module, function, arity} => percent} map that bypasses coverdata loading.

This parameter defaults to nil.

General Parameters

Like with all checks, general params can be applied.

Parameters can be configured via the .credo.exs config file.