diff --git a/src/lib.rs b/src/lib.rs
index f56447df65..739bf9a7c5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,13 +5,14 @@ use std::path::Path;
 use anyhow::Result;
 use log::debug;
 use rustpython_parser::lexer::LexResult;
+
 use settings::pyproject;
+use settings::Settings;
 
 use crate::autofix::fixer::Mode;
 use crate::linter::{check_path, tokenize};
 use crate::message::Message;
 use crate::settings::configuration::Configuration;
-use settings::Settings;
 
 mod ast;
 mod autofix;
diff --git a/src/pycodestyle/checks.rs b/src/pycodestyle/checks.rs
index 9285e68955..8b3a14caa3 100644
--- a/src/pycodestyle/checks.rs
+++ b/src/pycodestyle/checks.rs
@@ -1,8 +1,8 @@
-use crate::ast::operations::SourceCodeLocator;
 use itertools::izip;
 use rustpython_ast::Location;
 use rustpython_parser::ast::{Cmpop, Constant, Expr, ExprKind, Unaryop};
 
+use crate::ast::operations::SourceCodeLocator;
 use crate::ast::types::{CheckLocator, Range};
 use crate::checks::{Check, CheckKind, RejectedCmpop};
 
diff --git a/src/settings/configuration.rs b/src/settings/configuration.rs
index 2376999cd5..61a8267ecc 100644
--- a/src/settings/configuration.rs
+++ b/src/settings/configuration.rs
@@ -1,3 +1,6 @@
+//! User-provided program settings, taking into account pyproject.toml and command-line options.
+//! Structure mirrors the user-facing representation of the various parameters.
+
 use std::path::PathBuf;
 
 use anyhow::{anyhow, Result};
diff --git a/src/settings/mod.rs b/src/settings/mod.rs
index fc8dfbcaf0..19e6d978ea 100644
--- a/src/settings/mod.rs
+++ b/src/settings/mod.rs
@@ -131,3 +131,31 @@ fn resolve_codes(
     }
     codes
 }
+
+#[cfg(test)]
+mod tests {
+    use std::collections::BTreeSet;
+
+    use crate::checks::CheckCode;
+    use crate::checks_gen::CheckCodePrefix;
+    use crate::settings::resolve_codes;
+
+    #[test]
+    fn resolver() {
+        let actual = resolve_codes(&[CheckCodePrefix::W], &[], &[], &[]);
+        let expected = BTreeSet::from_iter([CheckCode::W292, CheckCode::W605]);
+        assert_eq!(actual, expected);
+
+        let actual = resolve_codes(&[CheckCodePrefix::W6], &[], &[], &[]);
+        let expected = BTreeSet::from_iter([CheckCode::W605]);
+        assert_eq!(actual, expected);
+
+        let actual = resolve_codes(&[CheckCodePrefix::W], &[], &[CheckCodePrefix::W292], &[]);
+        let expected = BTreeSet::from_iter([CheckCode::W605]);
+        assert_eq!(actual, expected);
+
+        let actual = resolve_codes(&[CheckCodePrefix::W605], &[], &[CheckCodePrefix::W605], &[]);
+        let expected = BTreeSet::from_iter([]);
+        assert_eq!(actual, expected);
+    }
+}