diff --git a/src/cli/mod.rs b/src/cli/mod.rs
index e69de29..8b13789 100644
--- a/src/cli/mod.rs
+++ b/src/cli/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/commit/mod.rs b/src/commit/mod.rs
index e69de29..cd40856 100644
--- a/src/commit/mod.rs
+++ b/src/commit/mod.rs
@@ -0,0 +1 @@
+pub mod types;
diff --git a/src/commit/types.rs b/src/commit/types.rs
new file mode 100644
index 0000000..85c33a5
--- /dev/null
+++ b/src/commit/types.rs
@@ -0,0 +1,277 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum CommitType {
+    Feat,
+    Fix,
+    Docs,
+    Style,
+    Refactor,
+    Perf,
+    Test,
+    Build,
+    Ci,
+    Chore,
+    Revert,
+}
+
+impl CommitType {
+    pub fn all() -> &'static [Self] {
+        &[
+            Self::Feat,
+            Self::Fix,
+            Self::Docs,
+            Self::Style,
+            Self::Refactor,
+            Self::Perf,
+            Self::Test,
+            Self::Build,
+            Self::Ci,
+            Self::Chore,
+            Self::Revert,
+        ]
+    }
+
+    pub const fn description(&self) -> &'static str {
+        match self {
+            Self::Feat => "A new feature",
+            Self::Fix => "A bug fix",
+            Self::Docs => "Documentation only changes",
+            Self::Style => "Changes that do not affect the meaning of the code",
+            Self::Refactor => "A code change that neither fixes a bug nor adds a feature",
+            Self::Perf => "A code change that improves performance",
+            Self::Test => "Adding missing tests or correcting existing tests",
+            Self::Build => "Changes that affect the build system or external dependencies",
+            Self::Ci => "Changes to CI configuration files and scripts",
+            Self::Chore => "Other changes that don't modify src or test files",
+            Self::Revert => "Reverts a previous commit",
+        }
+    }
+
+    pub const fn as_str(&self) -> &'static str {
+        match self {
+            Self::Feat => "feat",
+            Self::Fix => "fix",
+            Self::Docs => "docs",
+            Self::Style => "style",
+            Self::Refactor => "refactor",
+            Self::Perf => "perf",
+            Self::Test => "test",
+            Self::Build => "build",
+            Self::Ci => "ci",
+            Self::Chore => "chore",
+            Self::Revert => "revert",
+        }
+    }
+}
+
+impl std::fmt::Display for CommitType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.as_str())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Test that all 11 commit types exist and can be constructed
+    #[test]
+    fn all_eleven_variants_exist() {
+        // Exhaustive pattern matching ensures all variants exist at compile time
+        let variants = [
+            CommitType::Feat,
+            CommitType::Fix,
+            CommitType::Docs,
+            CommitType::Style,
+            CommitType::Refactor,
+            CommitType::Perf,
+            CommitType::Test,
+            CommitType::Build,
+            CommitType::Ci,
+            CommitType::Chore,
+            CommitType::Revert,
+        ];
+        assert_eq!(variants.len(), 11);
+    }
+
+    /// Test that as_str() returns the correct lowercase string for each variant
+    #[test]
+    fn as_str_returns_lowercase_string() {
+        assert_eq!(CommitType::Feat.as_str(), "feat");
+        assert_eq!(CommitType::Fix.as_str(), "fix");
+        assert_eq!(CommitType::Docs.as_str(), "docs");
+        assert_eq!(CommitType::Style.as_str(), "style");
+        assert_eq!(CommitType::Refactor.as_str(), "refactor");
+        assert_eq!(CommitType::Perf.as_str(), "perf");
+        assert_eq!(CommitType::Test.as_str(), "test");
+        assert_eq!(CommitType::Build.as_str(), "build");
+        assert_eq!(CommitType::Ci.as_str(), "ci");
+        assert_eq!(CommitType::Chore.as_str(), "chore");
+        assert_eq!(CommitType::Revert.as_str(), "revert");
+    }
+
+    /// Test that as_str() output is always lowercase (property-based check)
+    #[test]
+    fn as_str_is_always_lowercase() {
+        for commit_type in CommitType::all() {
+            let s = commit_type.as_str();
+            assert_eq!(
+                s,
+                s.to_lowercase(),
+                "as_str() should return lowercase for {:?}",
+                commit_type
+            );
+        }
+    }
+
+    /// Test that description() returns a non-empty string for each variant
+    #[test]
+    fn description_returns_non_empty_string() {
+        for commit_type in CommitType::all() {
+            let desc = commit_type.description();
+            assert!(
+                !desc.is_empty(),
+                "description() should not be empty for {:?}",
+                commit_type
+            );
+        }
+    }
+
+    /// Test that description() returns the expected descriptions per spec
+    #[test]
+    fn description_returns_expected_values() {
+        assert_eq!(CommitType::Feat.description(), "A new feature");
+        assert_eq!(CommitType::Fix.description(), "A bug fix");
+        assert_eq!(CommitType::Docs.description(), "Documentation only changes");
+        assert_eq!(
+            CommitType::Style.description(),
+            "Changes that do not affect the meaning of the code"
+        );
+        assert_eq!(
+            CommitType::Refactor.description(),
+            "A code change that neither fixes a bug nor adds a feature"
+        );
+        assert_eq!(
+            CommitType::Perf.description(),
+            "A code change that improves performance"
+        );
+        assert_eq!(
+            CommitType::Test.description(),
+            "Adding missing tests or correcting existing tests"
+        );
+        assert_eq!(
+            CommitType::Build.description(),
+            "Changes that affect the build system or external dependencies"
+        );
+        assert_eq!(
+            CommitType::Ci.description(),
+            "Changes to CI configuration files and scripts"
+        );
+        assert_eq!(
+            CommitType::Chore.description(),
+            "Other changes that don't modify src or test files"
+        );
+        assert_eq!(
+            CommitType::Revert.description(),
+            "Reverts a previous commit"
+        );
+    }
+
+    /// Test that all() returns exactly 11 types
+    #[test]
+    fn all_returns_eleven_types() {
+        assert_eq!(CommitType::all().len(), 11);
+    }
+
+    /// Test that all() returns types in the expected order (feat first, revert last)
+    #[test]
+    fn all_returns_types_in_expected_order() {
+        let all = CommitType::all();
+        assert_eq!(all[0], CommitType::Feat);
+        assert_eq!(all[1], CommitType::Fix);
+        assert_eq!(all[2], CommitType::Docs);
+        assert_eq!(all[3], CommitType::Style);
+        assert_eq!(all[4], CommitType::Refactor);
+        assert_eq!(all[5], CommitType::Perf);
+        assert_eq!(all[6], CommitType::Test);
+        assert_eq!(all[7], CommitType::Build);
+        assert_eq!(all[8], CommitType::Ci);
+        assert_eq!(all[9], CommitType::Chore);
+        assert_eq!(all[10], CommitType::Revert);
+    }
+
+    /// Test that all() contains all unique variants (no duplicates)
+    #[test]
+    fn all_contains_unique_variants() {
+        let all = CommitType::all();
+        for (i, variant) in all.iter().enumerate() {
+            for (j, other) in all.iter().enumerate() {
+                if i != j {
+                    assert_ne!(variant, other, "all() should not contain duplicates");
+                }
+            }
+        }
+    }
+
+    /// Test that Display implementation delegates to as_str()
+    #[test]
+    fn display_delegates_to_as_str() {
+        for commit_type in CommitType::all() {
+            let display_output = format!("{}", commit_type);
+            let as_str_output = commit_type.as_str();
+            assert_eq!(
+                display_output, as_str_output,
+                "Display should delegate to as_str() for {:?}",
+                commit_type
+            );
+        }
+    }
+
+    /// Test Display for specific variants
+    #[test]
+    fn display_shows_lowercase_type() {
+        assert_eq!(format!("{}", CommitType::Feat), "feat");
+        assert_eq!(format!("{}", CommitType::Fix), "fix");
+        assert_eq!(format!("{}", CommitType::Docs), "docs");
+        assert_eq!(format!("{}", CommitType::Style), "style");
+        assert_eq!(format!("{}", CommitType::Refactor), "refactor");
+        assert_eq!(format!("{}", CommitType::Perf), "perf");
+        assert_eq!(format!("{}", CommitType::Test), "test");
+        assert_eq!(format!("{}", CommitType::Build), "build");
+        assert_eq!(format!("{}", CommitType::Ci), "ci");
+        assert_eq!(format!("{}", CommitType::Chore), "chore");
+        assert_eq!(format!("{}", CommitType::Revert), "revert");
+    }
+
+    /// Test that CommitType implements Copy (can be used after move)
+    #[test]
+    fn commit_type_is_copy() {
+        let original = CommitType::Feat;
+        let copied = original; // Copy, not move
+        assert_eq!(original, copied); // original still usable
+    }
+
+    /// Test that CommitType implements PartialEq correctly
+    #[test]
+    fn commit_type_equality() {
+        assert_eq!(CommitType::Feat, CommitType::Feat);
+        assert_ne!(CommitType::Feat, CommitType::Fix);
+    }
+
+    /// Test that CommitType can be used as HashMap key (Hash + Eq)
+    #[test]
+    fn commit_type_can_be_hash_key() {
+        use std::collections::HashMap;
+        let mut map = HashMap::new();
+        map.insert(CommitType::Feat, "feature");
+        map.insert(CommitType::Fix, "bugfix");
+        assert_eq!(map.get(&CommitType::Feat), Some(&"feature"));
+        assert_eq!(map.get(&CommitType::Fix), Some(&"bugfix"));
+    }
+
+    /// Test that Debug is implemented
+    #[test]
+    fn commit_type_has_debug() {
+        let debug_output = format!("{:?}", CommitType::Feat);
+        assert!(debug_output.contains("Feat"));
+    }
+}
diff --git a/src/error.rs b/src/error.rs
index 48a5f40..32910d9 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -16,5 +16,5 @@ pub enum Error {
     #[error("Operation cancelled by user")]
     Cancelled,
     #[error("Non-interactive terminal detected")]
-    NonInteractive
+    NonInteractive,
 }
diff --git a/src/jj/mod.rs b/src/jj/mod.rs
index e69de29..8b13789 100644
--- a/src/jj/mod.rs
+++ b/src/jj/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/lib.rs b/src/lib.rs
index 1b4308e..36bdc97 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,5 +1,5 @@
 mod cli;
 mod commit;
+mod error;
 mod jj;
 mod prompts;
-mod error;
diff --git a/src/prompts/mod.rs b/src/prompts/mod.rs
index e69de29..8b13789 100644
--- a/src/prompts/mod.rs
+++ b/src/prompts/mod.rs
@@ -0,0 +1 @@
+