diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 781a5e1..3e44454 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -35,6 +35,9 @@ jobs:
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
 
+      - name: Run repo script tests
+        run: pnpm test:scripts
+
       - name: Check architecture guardrails
         run: pnpm check:architecture
 
diff --git a/package.json b/package.json
index 2d368bb..bf15332 100644
--- a/package.json
+++ b/package.json
@@ -11,6 +11,7 @@
     "test": "node ./scripts/run-from-workspace-root.mjs turbo run test:unit",
     "test:unit": "node ./scripts/run-from-workspace-root.mjs turbo test:unit",
     "test:e2e": "node ./scripts/run-from-workspace-root.mjs turbo test:e2e",
+    "test:scripts": "node --test scripts/*.test.mjs",
     "check:architecture": "node ./scripts/check-architecture-guardrails.mjs",
     "check:exports": "node ./scripts/check-workspace-exports.mjs",
     "check:imports": "node ./scripts/check-workspace-imports.mjs",
diff --git a/scripts/worktree-hygiene.mjs b/scripts/worktree-hygiene.mjs
index 42cb0dd..44d1eb5 100644
--- a/scripts/worktree-hygiene.mjs
+++ b/scripts/worktree-hygiene.mjs
@@ -2,9 +2,10 @@
 
 import { execFileSync } from "node:child_process";
 import process from "node:process";
+import { pathToFileURL } from "node:url";
 
-function printUsage() {
-  console.log(`Usage:
+export function renderUsage() {
+  return `Usage:
   node scripts/worktree-hygiene.mjs [--scope <path>]... [--allow-outside-scope] [--fail-outside-scope] [--fail-on-dirty] [--json]
 
 Examples:
@@ -13,19 +14,20 @@ Examples:
   node scripts/worktree-hygiene.mjs --scope docs/ --scope scripts/ --fail-outside-scope
   node scripts/worktree-hygiene.mjs --fail-on-dirty
   node scripts/worktree-hygiene.mjs --scope packages/api/src/router/ --allow-outside-scope
-`);
+`;
 }
 
-function normalizeScope(scope) {
+export function normalizeScope(scope) {
   return scope.replace(/\\/gu, "/").replace(/^\.\/+/u, "");
 }
 
-function parseArgs(argv) {
+export function parseArgs(argv) {
   const scopes = [];
   let allowOutsideScope = false;
   let failOutsideScope = false;
   let failOnDirty = false;
   let json = false;
+  let help = false;
 
   for (let index = 0; index < argv.length; index += 1) {
     const arg = argv[index];
@@ -58,23 +60,23 @@ function parseArgs(argv) {
       continue;
     }
     if (arg === "--help" || arg === "-h") {
-      printUsage();
-      process.exit(0);
+      help = true;
+      continue;
     }
     throw new Error(`Unknown argument: ${arg}`);
   }
 
-  return { scopes, allowOutsideScope, failOutsideScope, failOnDirty, json };
+  return { scopes, allowOutsideScope, failOutsideScope, failOnDirty, json, help };
 }
 
-function runGit(args) {
+export function runGit(args) {
   return execFileSync("git", args, {
     encoding: "utf8",
     stdio: ["ignore", "pipe", "pipe"],
   });
 }
 
-function parsePorcelain(output) {
+export function parsePorcelain(output) {
   return output
     .split("\n")
     .filter(Boolean)
@@ -90,11 +92,11 @@ function parsePorcelain(output) {
     });
 }
 
-function matchesScope(path, scopes) {
+export function matchesScope(path, scopes) {
   return scopes.some((scope) => path === scope || path.startsWith(scope.endsWith("/") ? scope : `${scope}/`));
 }
 
-function summarize(entries) {
+export function summarize(entries) {
   const summary = {
     staged: 0,
     unstaged: 0,
@@ -117,18 +119,14 @@ function summarize(entries) {
   return summary;
 }
 
-function formatEntries(title, entries) {
+export function formatEntries(title, entries) {
   if (entries.length === 0) {
     return `${title}: none`;
   }
   return `${title}:\n${entries.map((entry) => `- ${entry.xy} ${entry.path}`).join("\n")}`;
 }
 
-function main() {
-  const { scopes, allowOutsideScope, failOutsideScope, failOnDirty, json } = parseArgs(process.argv.slice(2));
-  const root = runGit(["rev-parse", "--show-toplevel"]).trim();
-  const branch = runGit(["rev-parse", "--abbrev-ref", "HEAD"]).trim();
-  const entries = parsePorcelain(runGit(["status", "--short"]));
+function renderReport({ root, branch, scopes, allowOutsideScope, failOutsideScope, failOnDirty, json, entries }) {
   const inScope = scopes.length === 0 ? entries : entries.filter((entry) => matchesScope(entry.path, scopes));
   const outOfScope = scopes.length === 0 ? [] : entries.filter((entry) => !matchesScope(entry.path, scopes));
   const status = {
@@ -143,44 +141,96 @@ function main() {
     failOnDirty,
   };
 
+  const lines = [];
   if (json) {
-    console.log(JSON.stringify({ ...status, entries: { inScope, outOfScope } }, null, 2));
+    lines.push(JSON.stringify({ ...status, entries: { inScope, outOfScope } }, null, 2));
   } else {
-    console.log(`Repository: ${root}`);
-    console.log(`Branch: ${branch}`);
-    console.log(`Dirty entries: ${entries.length}`);
-    console.log(
+    lines.push(`Repository: ${root}`);
+    lines.push(`Branch: ${branch}`);
+    lines.push(`Dirty entries: ${entries.length}`);
+    lines.push(
       `Summary: staged=${status.totals.staged}, unstaged=${status.totals.unstaged}, untracked=${status.totals.untracked}`,
     );
     if (scopes.length > 0) {
-      console.log(`Owned scope: ${scopes.join(", ")}`);
-      console.log(formatEntries("In scope", inScope));
-      console.log(formatEntries("Outside scope", outOfScope));
+      lines.push(`Owned scope: ${scopes.join(", ")}`);
+      lines.push(formatEntries("In scope", inScope));
+      lines.push(formatEntries("Outside scope", outOfScope));
       if (outOfScope.length > 0 && !allowOutsideScope) {
-        console.log("\nResult: outside-scope changes detected.");
+        lines.push("", "Result: outside-scope changes detected.");
       } else if (outOfScope.length > 0) {
-        console.log("\nResult: outside-scope changes detected but tolerated by flag.");
+        lines.push("", "Result: outside-scope changes detected but tolerated by flag.");
       } else {
-        console.log("\nResult: all dirty files are inside the declared scope.");
+        lines.push("", "Result: all dirty files are inside the declared scope.");
       }
     } else {
-      console.log(formatEntries("Dirty files", entries));
+      lines.push(formatEntries("Dirty files", entries));
     }
   }
 
+  let exitCode = 0;
   if (failOnDirty && entries.length > 0) {
-    process.exit(1);
+    exitCode = 1;
   }
 
   if (scopes.length > 0 && outOfScope.length > 0 && (failOutsideScope || !allowOutsideScope)) {
-    process.exit(2);
+    exitCode = 2;
+  }
+
+  return {
+    exitCode,
+    output: lines.join("\n"),
+    status,
+    entries: {
+      inScope,
+      outOfScope,
+    },
+  };
+}
+
+export function inspectWorktreeHygiene(argv, git = runGit) {
+  const { scopes, allowOutsideScope, failOutsideScope, failOnDirty, json, help } = parseArgs(argv);
+  if (help) {
+    return {
+      exitCode: 0,
+      output: renderUsage(),
+      status: null,
+      entries: {
+        inScope: [],
+        outOfScope: [],
+      },
+    };
+  }
+
+  const root = git(["rev-parse", "--show-toplevel"]).trim();
+  const branch = git(["rev-parse", "--abbrev-ref", "HEAD"]).trim();
+  const entries = parsePorcelain(git(["status", "--short"]));
+
+  return renderReport({
+    root,
+    branch,
+    scopes,
+    allowOutsideScope,
+    failOutsideScope,
+    failOnDirty,
+    json,
+    entries,
+  });
+}
+
+function main() {
+  const result = inspectWorktreeHygiene(process.argv.slice(2));
+  console.log(result.output);
+  if (result.exitCode !== 0) {
+    process.exit(result.exitCode);
   }
 }
 
-try {
-  main();
-} catch (error) {
-  console.error(error instanceof Error ? error.message : String(error));
-  printUsage();
-  process.exit(1);
+if (import.meta.url === pathToFileURL(process.argv[1]).href) {
+  try {
+    main();
+  } catch (error) {
+    console.error(error instanceof Error ? error.message : String(error));
+    console.error(renderUsage());
+    process.exit(1);
+  }
 }
diff --git a/scripts/worktree-hygiene.test.mjs b/scripts/worktree-hygiene.test.mjs
new file mode 100644
index 0000000..4419091
--- /dev/null
+++ b/scripts/worktree-hygiene.test.mjs
@@ -0,0 +1,93 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import {
+  inspectWorktreeHygiene,
+  parseArgs,
+  parsePorcelain,
+} from "./worktree-hygiene.mjs";
+
+function createGitStub(statusOutput) {
+  return (args) => {
+    if (args[0] === "rev-parse" && args[1] === "--show-toplevel") {
+      return "/tmp/capakraken\n";
+    }
+    if (args[0] === "rev-parse" && args[1] === "--abbrev-ref") {
+      return "main\n";
+    }
+    if (args[0] === "status" && args[1] === "--short") {
+      return statusOutput;
+    }
+
+    throw new Error(`Unexpected git args: ${args.join(" ")}`);
+  };
+}
+
+describe("worktree hygiene", () => {
+  it("fails when a scope value is missing", () => {
+    assert.throws(() => parseArgs(["--scope"]), /--scope requires a path value\./);
+  });
+
+  it("fails on unknown arguments", () => {
+    assert.throws(() => parseArgs(["--wat"]), /Unknown argument: --wat/);
+  });
+
+  it("normalizes rename targets in porcelain output", () => {
+    assert.deepEqual(parsePorcelain("R  docs/old.md -> docs/new.md\n"), [
+      {
+        xy: "R ",
+        path: "docs/new.md",
+      },
+    ]);
+  });
+
+  it("returns exit code 1 when fail-on-dirty is enabled", () => {
+    const result = inspectWorktreeHygiene(
+      ["--fail-on-dirty"],
+      createGitStub(" M scripts/worktree-hygiene.mjs\n?? scripts/worktree-hygiene.test.mjs\n"),
+    );
+
+    assert.equal(result.exitCode, 1);
+    assert.match(result.output, /Dirty entries: 2/);
+    assert.equal(result.status?.totals.untracked, 1);
+  });
+
+  it("returns exit code 2 when dirty files escape the declared scope", () => {
+    const result = inspectWorktreeHygiene(
+      ["--scope", "docs/", "--fail-outside-scope"],
+      createGitStub(" M docs/guide.md\n M scripts/worktree-hygiene.mjs\n"),
+    );
+
+    assert.equal(result.exitCode, 2);
+    assert.equal(result.entries.outOfScope.length, 1);
+    assert.match(result.output, /outside-scope changes detected\./);
+  });
+
+  it("keeps fail-outside-scope authoritative even when allow-outside-scope is set", () => {
+    const result = inspectWorktreeHygiene(
+      ["--scope", ".\\docs", "--allow-outside-scope", "--fail-outside-scope", "--json"],
+      createGitStub(" M docs/guide.md\n M scripts/worktree-hygiene.mjs\n"),
+    );
+
+    assert.equal(result.exitCode, 2);
+
+    const parsed = JSON.parse(result.output);
+    assert.equal(parsed.scopes[0], "docs");
+    assert.equal(parsed.inScope, 1);
+    assert.equal(parsed.outOfScope, 1);
+  });
+
+  it("tolerates outside-scope files when explicitly allowed and emits json", () => {
+    const result = inspectWorktreeHygiene(
+      ["--scope", "docs/", "--allow-outside-scope", "--json"],
+      createGitStub("R  docs/old.md -> docs/new.md\n?? scripts/worktree-hygiene.test.mjs\n"),
+    );
+
+    assert.equal(result.exitCode, 0);
+
+    const parsed = JSON.parse(result.output);
+    assert.equal(parsed.inScope, 1);
+    assert.equal(parsed.outOfScope, 1);
+    assert.deepEqual(parsed.entries.inScope, [{ xy: "R ", path: "docs/new.md" }]);
+    assert.deepEqual(parsed.entries.outOfScope, [{ xy: "??", path: "scripts/worktree-hygiene.test.mjs" }]);
+  });
+});