diff --git a/tests/parent-upgrade.test.ts b/tests/parent-upgrade.test.ts
new file mode 100644
index 0000000..7228f0e
--- /dev/null
+++ b/tests/parent-upgrade.test.ts
@@ -0,0 +1,198 @@
+import { jest } from "@jest/globals";
+import type { Finding, PackageRef } from "../src/types.js";
+
+const fetchMock = jest.fn();
+global.fetch = fetchMock as unknown as typeof fetch;
+
+function createPackages(): PackageRef[] {
+  return [
+    {
+      name: "app",
+      version: "1.0.0",
+      ecosystem: "npm",
+      paths: [["project", "app"]],
+    },
+    {
+      name: "mid",
+      version: "2.0.0",
+      ecosystem: "npm",
+      paths: [["project", "app", "mid"]],
+    },
+    {
+      name: "lodash",
+      version: "4.17.20",
+      ecosystem: "npm",
+      paths: [
+        ["project", "app", "lodash"],
+        ["project", "app", "mid", "lodash"],
+      ],
+    },
+  ];
+}
+
+function createFinding(overrides?: Partial<Finding>): Finding {
+  return {
+    pkg: {
+      name: "lodash",
+      version: "4.17.20",
+      ecosystem: "npm",
+      paths: [["project", "app", "lodash"]],
+    },
+    vulnerabilities: [{ id: "OSV-123" }],
+    severity: "high",
+    cveAliases: [],
+    dependencyPaths: [["project", "app", "lodash"]],
+    relationship: "transitive",
+    firstFixedVersion: "4.17.21",
+    recommendedParentUpgrade: undefined,
+    ...overrides,
+  };
+}
+
+function mockPackument(data: unknown, ok = true) {
+  fetchMock.mockResolvedValue({
+    ok,
+    json: async () => data,
+  });
+}
+
+async function loadResolver() {
+  const module = await import(`../src/remediation/parent-upgrade.js?test=${Date.now()}-${Math.random()}`);
+  return module.resolveRecommendedParentUpgrade;
+}
+
+describe("resolveRecommendedParentUpgrade", () => {
+  beforeEach(() => {
+    fetchMock.mockReset();
+  });
+
+  it("returns null for non-transitive findings or missing usable paths", async () => {
+    const resolveRecommendedParentUpgrade = await loadResolver();
+    const packages = createPackages();
+
+    await expect(
+      resolveRecommendedParentUpgrade(
+        createFinding({ relationship: "direct" }),
+        packages,
+      ),
+    ).resolves.toBeNull();
+
+    await expect(
+      resolveRecommendedParentUpgrade(
+        createFinding({ dependencyPaths: [], pkg: { name: "lodash", version: "4.17.20", ecosystem: "npm" } }),
+        packages,
+      ),
+    ).resolves.toBeNull();
+
+    expect(fetchMock).not.toHaveBeenCalled();
+  });
+
+  it("returns null when the direct parent cannot be found in the package list", async () => {
+    const resolveRecommendedParentUpgrade = await loadResolver();
+    const finding = createFinding({
+      dependencyPaths: [["project", "missing-parent", "lodash"]],
+    });
+
+    await expect(resolveRecommendedParentUpgrade(finding, createPackages())).resolves.toBeNull();
+    expect(fetchMock).not.toHaveBeenCalled();
+  });
+
+  it("recommends an exact direct-child parent upgrade when a newer parent stops allowing the vulnerable version", async () => {
+    const resolveRecommendedParentUpgrade = await loadResolver();
+    mockPackument({
+      versions: {
+        "1.0.0": { dependencies: { lodash: "^4.17.20" } },
+        "1.0.5": { dependencies: { lodash: "^4.17.20" } },
+        "1.1.0": { dependencies: { lodash: "^4.17.21" } },
+      },
+    });
+
+    const result = await resolveRecommendedParentUpgrade(createFinding(), createPackages());
+
+    expect(result).toMatchObject({
+      package: "app",
+      currentVersion: "1.0.0",
+      targetVersion: "1.1.0",
+      vulnerablePackage: "lodash",
+      confidence: "exact-direct-child",
+    });
+    expect(result?.reason).toContain("no longer allows lodash@4.17.20");
+    expect(result?.reason).toContain("allows 4.17.21+");
+  });
+
+  it("recommends a best-effort upgrade for deeper paths when the direct parent stops allowing the current intermediate version", async () => {
+    const resolveRecommendedParentUpgrade = await loadResolver();
+    mockPackument({
+      versions: {
+        "1.0.0": { dependencies: { mid: "^2.0.0" } },
+        "1.1.0": { dependencies: { mid: "^2.0.0" } },
+        "2.0.0": { dependencies: { mid: "^3.0.0" } },
+      },
+    });
+
+    const finding = createFinding({
+      dependencyPaths: [["project", "app", "mid", "lodash"]],
+      pkg: {
+        name: "lodash",
+        version: "4.17.20",
+        ecosystem: "npm",
+        paths: [["project", "app", "mid", "lodash"]],
+      },
+    });
+
+    const result = await resolveRecommendedParentUpgrade(finding, createPackages());
+
+    expect(result).toMatchObject({
+      package: "app",
+      currentVersion: "1.0.0",
+      targetVersion: "2.0.0",
+      vulnerablePackage: "lodash",
+      confidence: "best-effort",
+    });
+    expect(result?.reason).toContain("no longer allows mid@2.0.0");
+  });
+
+  it("returns null when the immediate parent version is missing or invalid in deeper paths", async () => {
+    const resolveRecommendedParentUpgrade = await loadResolver();
+    mockPackument({
+      versions: {
+        "1.1.0": { dependencies: { mid: "^3.0.0" } },
+      },
+    });
+
+    const packages: PackageRef[] = [
+      {
+        name: "app",
+        version: "1.0.0",
+        ecosystem: "npm",
+        paths: [["project", "app"]],
+      },
+      {
+        name: "lodash",
+        version: "4.17.20",
+        ecosystem: "npm",
+        paths: [["project", "app", "mid", "lodash"]],
+      },
+    ];
+
+    const finding = createFinding({
+      dependencyPaths: [["project", "app", "mid", "lodash"]],
+      pkg: {
+        name: "lodash",
+        version: "4.17.20",
+        ecosystem: "npm",
+        paths: [["project", "app", "mid", "lodash"]],
+      },
+    });
+
+    await expect(resolveRecommendedParentUpgrade(finding, packages)).resolves.toBeNull();
+  });
+
+  it("returns null when the registry packument cannot be fetched successfully", async () => {
+    const resolveRecommendedParentUpgrade = await loadResolver();
+    mockPackument({}, false);
+
+    await expect(resolveRecommendedParentUpgrade(createFinding(), createPackages())).resolves.toBeNull();
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+  });
+});