diff --git a/review-enrichment/test/actions-pin.test.ts b/review-enrichment/test/actions-pin.test.ts
new file mode 100644
index 0000000000..0c25cb035e
--- /dev/null
+++ b/review-enrichment/test/actions-pin.test.ts
@@ -0,0 +1,120 @@
+// Units for the GitHub Actions pin analyzer (#1500/#2101). Kept separate so analyzer PRs avoid collisions.
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import {
+  scanActionPins,
+  scanWorkflowPins,
+} from "../dist/analyzers/actions-pin.js";
+
+const workflowPath = ".github/workflows/ci.yml";
+const fullSha = "0123456789abcdef0123456789abcdef01234567";
+
+test("scanWorkflowPins flags mutable third-party action refs with line citations", () => {
+  const findings = scanWorkflowPins(
+    workflowPath,
+    [
+      "@@ -1,0 +10,7 @@",
+      "+    - uses: pnpm/action-setup@v3",
+      "+    - uses: docker/login-action@main",
+      `+    - uses: thirdparty/pinned@${fullSha}`,
+      "+    - uses: actions/checkout@v4",
+      "+    - uses: github/codeql-action/init@v3",
+      "+    - run: npm test",
+      "-    - uses: stale/action@main",
+    ].join("\n"),
+  );
+
+  assert.deepEqual(findings, [
+    { file: workflowPath, line: 10, action: "pnpm/action-setup", ref: "v3" },
+    {
+      file: workflowPath,
+      line: 11,
+      action: "docker/login-action",
+      ref: "main",
+    },
+  ]);
+});
+
+test("scanWorkflowPins accepts quoted uses keys and ignores unchanged uses lines", () => {
+  const findings = scanWorkflowPins(
+    workflowPath,
+    [
+      "@@ -8,2 +8,4 @@",
+      "     steps:",
+      "       - uses: mutable/unchanged@main",
+      '+      "uses": "vendor/quoted-action@release"',
+      "+      'uses': 'vendor/single-quoted@beta'",
+    ].join("\n"),
+  );
+
+  assert.deepEqual(findings, [
+    {
+      file: workflowPath,
+      line: 10,
+      action: "vendor/quoted-action",
+      ref: "release",
+    },
+    {
+      file: workflowPath,
+      line: 11,
+      action: "vendor/single-quoted",
+      ref: "beta",
+    },
+  ]);
+});
+
+test("scanWorkflowPins ignores patches without added mutable third-party uses", () => {
+  assert.deepEqual(
+    scanWorkflowPins(
+      workflowPath,
+      [
+        "@@ -1,0 +1,4 @@",
+        "+name: ci",
+        "+jobs:",
+        `+    - uses: vendor/pinned@${fullSha}`,
+        "+    - uses: actions/setup-node@v4",
+      ].join("\n"),
+    ),
+    [],
+  );
+});
+
+test("scanActionPins scans only changed workflow YAML files with patches", async () => {
+  const findings = await scanActionPins({
+    repoFullName: "o/r",
+    prNumber: 1,
+    files: [
+      {
+        path: ".github/workflows/release.yaml",
+        patch: "@@ -1,0 +20,1 @@\n+    - uses: softprops/action-gh-release@v2",
+      },
+      {
+        path: ".github/workflows/ci.yml",
+        patch: "@@ -1,0 +30,1 @@\n+    - uses: pnpm/action-setup@v3",
+      },
+      {
+        path: "docs/workflow.yml",
+        patch: "@@ -1,0 +1,1 @@\n+    - uses: vendor/not-a-workflow@main",
+      },
+      {
+        path: ".github/workflows/no-patch.yml",
+      },
+    ],
+  });
+
+  assert.deepEqual(findings, [
+    {
+      file: ".github/workflows/release.yaml",
+      line: 20,
+      action: "softprops/action-gh-release",
+      ref: "v2",
+    },
+    {
+      file: ".github/workflows/ci.yml",
+      line: 30,
+      action: "pnpm/action-setup",
+      ref: "v3",
+    },
+  ]);
+});