diff --git a/tests/unit/modules/commits/commit.mapper.test.ts b/tests/unit/modules/commits/commit.mapper.test.ts
new file mode 100644
index 0000000..d7797f7
--- /dev/null
+++ b/tests/unit/modules/commits/commit.mapper.test.ts
@@ -0,0 +1,175 @@
+import {
+    mapCommit,
+    mapCommits,
+} from "../../../../src/modules/commits/commit.mapper";
+import { CommitDTO } from "../../../../src/modules/commits/commit.dto";
+import { UserDTO } from "../../../../src/modules/users/user.dto";
+
+const mockUserDto: UserDTO = {
+    login: "octocat",
+    id: 1,
+    node_id: "U_1",
+    avatar_url: "",
+    html_url: "",
+    url: "",
+    type: "User",
+    site_admin: false,
+    name: null,
+    company: null,
+    blog: null,
+    location: null,
+    email: null,
+    bio: null,
+    twitter_username: null,
+    public_repos: 0,
+    public_gists: 0,
+    followers: 0,
+    following: 0,
+    created_at: "2020-01-01T00:00:00Z",
+    updated_at: "2020-01-01T00:00:00Z",
+};
+
+const mockCommitDto: CommitDTO = {
+    sha: "abc123",
+    node_id: "C_1",
+    commit: {
+        author: {
+            name: "Mona Lisa",
+            email: "mona@example.com",
+            date: "2024-01-01T10:00:00Z",
+        },
+        committer: {
+            name: "GitHub",
+            email: "noreply@github.com",
+            date: "2024-01-02T10:00:00Z",
+        },
+        message: "fix: handle null user",
+        tree: {
+            sha: "tree123",
+            url: "https://api.github.com/repos/owner/repo/git/trees/tree123",
+        },
+        url: "https://api.github.com/repos/owner/repo/git/commits/abc123",
+        comment_count: 2,
+        verification: {
+            verified: false,
+            reason: "unsigned",
+            signature: null,
+            payload: null,
+        },
+    },
+    url: "https://api.github.com/repos/owner/repo/commits/abc123",
+    html_url: "https://github.com/owner/repo/commit/abc123",
+    author: mockUserDto,
+    committer: mockUserDto,
+    parents: [
+        {
+            sha: "parent1",
+            url: "https://api.github.com/repos/owner/repo/commits/parent1",
+            html_url: "https://github.com/owner/repo/commit/parent1",
+        },
+    ],
+};
+
+describe("commit.mapper", () => {
+    describe("mapCommit", () => {
+        it("maps snake_case DTO fields to camelCase", () => {
+            const result = mapCommit(mockCommitDto);
+            expect(result.sha).toBe("abc123");
+            expect(result.nodeId).toBe("C_1");
+            expect(result.message).toBe("fix: handle null user");
+            expect(result.commentCount).toBe(2);
+        });
+
+        it("uses html_url for url, not the API url", () => {
+            const result = mapCommit(mockCommitDto);
+            expect(result.url).toBe(
+                "https://github.com/owner/repo/commit/abc123",
+            );
+        });
+
+        it("converts author and committer dates to Date instances", () => {
+            const result = mapCommit(mockCommitDto);
+            expect(result.author.date).toBeInstanceOf(Date);
+            expect(result.author.date.toISOString()).toBe(
+                "2024-01-01T10:00:00.000Z",
+            );
+            expect(result.committer.date).toBeInstanceOf(Date);
+            expect(result.committer.date.toISOString()).toBe(
+                "2024-01-02T10:00:00.000Z",
+            );
+        });
+
+        it("maps the GitHub user onto author and committer when present", () => {
+            const result = mapCommit(mockCommitDto);
+            expect(result.author.user?.username).toBe("octocat");
+            expect(result.committer.user?.username).toBe("octocat");
+        });
+
+        it("maps author.user to null when the commit author has no GitHub account", () => {
+            const result = mapCommit({ ...mockCommitDto, author: null });
+            expect(result.author.user).toBeNull();
+            // The git-level identity is still there.
+            expect(result.author.name).toBe("Mona Lisa");
+            expect(result.author.email).toBe("mona@example.com");
+        });
+
+        it("maps committer.user to null when the committer has no GitHub account", () => {
+            const result = mapCommit({ ...mockCommitDto, committer: null });
+            expect(result.committer.user).toBeNull();
+            expect(result.committer.name).toBe("GitHub");
+        });
+
+        it("takes verified from the verification block", () => {
+            expect(mapCommit(mockCommitDto).verified).toBe(false);
+            const signed: CommitDTO = {
+                ...mockCommitDto,
+                commit: {
+                    ...mockCommitDto.commit,
+                    verification: {
+                        verified: true,
+                        reason: "valid",
+                        signature: "-----BEGIN PGP SIGNATURE-----",
+                        payload: "tree tree123",
+                    },
+                },
+            };
+            expect(mapCommit(signed).verified).toBe(true);
+        });
+
+        it("maps parents to their shas", () => {
+            const merge: CommitDTO = {
+                ...mockCommitDto,
+                parents: [
+                    ...mockCommitDto.parents,
+                    {
+                        sha: "parent2",
+                        url: "https://api.github.com/repos/owner/repo/commits/parent2",
+                        html_url:
+                            "https://github.com/owner/repo/commit/parent2",
+                    },
+                ],
+            };
+            expect(mapCommit(merge).parentShas).toEqual(["parent1", "parent2"]);
+        });
+
+        it("maps a root commit (no parents) to an empty array", () => {
+            const root = mapCommit({ ...mockCommitDto, parents: [] });
+            expect(root.parentShas).toEqual([]);
+        });
+    });
+
+    describe("mapCommits", () => {
+        it("maps an array of commits", () => {
+            const result = mapCommits([
+                mockCommitDto,
+                { ...mockCommitDto, sha: "def456" },
+            ]);
+            expect(result).toHaveLength(2);
+            expect(result[1].sha).toBe("def456");
+        });
+
+        it("maps an empty array to an empty array", () => {
+            expect(mapCommits([])).toEqual([]);
+        });
+    });
+});