diff --git a/tools/hygiene/check-github-settings-drift.test.ts b/tools/hygiene/check-github-settings-drift.test.ts
new file mode 100644
index 0000000000..0a79c738c4
--- /dev/null
+++ b/tools/hygiene/check-github-settings-drift.test.ts
@@ -0,0 +1,88 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+
+import { parseArgs } from "./check-github-settings-drift";
+
+let priorGhRepo: string | undefined;
+
+beforeEach(() => {
+  priorGhRepo = process.env["GH_REPO"];
+  delete process.env["GH_REPO"];
+});
+
+afterEach(() => {
+  if (priorGhRepo === undefined) delete process.env["GH_REPO"];
+  else process.env["GH_REPO"] = priorGhRepo;
+});
+
+describe("parseArgs", () => {
+  test("--repo OWNER/NAME → success and default expected path", async () => {
+    const result = await parseArgs(["--repo", "Lucent-Financial-Group/Zeta"]);
+
+    expect(result.kind).toBe("args");
+    if (result.kind === "args") {
+      expect(result.args.repo).toBe("Lucent-Financial-Group/Zeta");
+      expect(result.args.expected).toMatch(/github-settings\.expected\.json$/);
+    }
+  });
+
+  test("--expected PATH overrides default", async () => {
+    const result = await parseArgs([
+      "--repo",
+      "AceHack/Zeta",
+      "--expected",
+      "/tmp/custom-snapshot.json",
+    ]);
+
+    expect(result.kind).toBe("args");
+    if (result.kind === "args") {
+      expect(result.args.expected).toBe("/tmp/custom-snapshot.json");
+    }
+  });
+
+  test("--repo without value returns an error", async () => {
+    const result = await parseArgs(["--repo"]);
+
+    expect(result.kind).toBe("error");
+    if (result.kind === "error") {
+      expect(result.message).toContain("--repo requires OWNER/NAME argument");
+    }
+  });
+
+  test("--expected without value returns an error", async () => {
+    const result = await parseArgs(["--repo", "owner/name", "--expected"]);
+
+    expect(result.kind).toBe("error");
+    if (result.kind === "error") {
+      expect(result.message).toContain("--expected requires PATH argument");
+    }
+  });
+
+  test("unknown flag returns an error", async () => {
+    const result = await parseArgs(["--bogus"]);
+
+    expect(result.kind).toBe("error");
+    if (result.kind === "error") {
+      expect(result.message).toContain("unknown arg");
+    }
+  });
+
+  test("falls back to GH_REPO env var when no argv", async () => {
+    process.env["GH_REPO"] = "env/zeta";
+    const result = await parseArgs([]);
+
+    expect(result.kind).toBe("args");
+    if (result.kind === "args") {
+      expect(result.args.repo).toBe("env/zeta");
+    }
+  });
+
+  test("explicit --repo overrides GH_REPO env var", async () => {
+    process.env["GH_REPO"] = "env/zeta";
+    const result = await parseArgs(["--repo", "argv/zeta"]);
+
+    expect(result.kind).toBe("args");
+    if (result.kind === "args") {
+      expect(result.args.repo).toBe("argv/zeta");
+    }
+  });
+});
diff --git a/tools/hygiene/check-github-settings-drift.ts b/tools/hygiene/check-github-settings-drift.ts
index ed9971dad1..f7b5b7132a 100644
--- a/tools/hygiene/check-github-settings-drift.ts
+++ b/tools/hygiene/check-github-settings-drift.ts
@@ -54,7 +54,7 @@ type ParseResult =
   | { readonly kind: "args"; readonly args: Args }
   | { readonly kind: "error"; readonly message: string };
 
-async function parseArgs(argv: readonly string[]): Promise<ParseResult> {
+export async function parseArgs(argv: readonly string[]): Promise<ParseResult> {
   let repo = "";
   let expected = resolve(SCRIPT_DIR, "github-settings.expected.json");
   let i = 0;