fix claim validation and expert branch scoping

src/fanavaran/fanavaran-location.service.spec.ts

@@ -0,0 +1,55 @@
+import { ForbiddenException } from "@nestjs/common";
+import { FanavaranLocationService } from "./fanavaran-location.service";
+
+describe("FanavaranLocationService branch scope", () => {
+  const makerId = "maker-1";
+  const reviewerId = "reviewer-1";
+
+  const createService = (makerBranch?: string, reviewerBranch?: string) =>
+    new FanavaranLocationService(
+      {
+        findById: jest.fn().mockResolvedValue(
+          makerBranch ? { branchId: makerBranch } : {},
+        ),
+      } as any,
+      {
+        findById: jest.fn().mockResolvedValue(
+          reviewerBranch ? { branchId: reviewerBranch } : {},
+        ),
+      } as any,
+    );
+
+  it("allows a reviewer to view a file from the same branch", async () => {
+    const service = createService("branch-1", "branch-1");
+
+    await expect(
+      service.assertMakerReviewerBranchCompatible({
+        fileMakerId: makerId,
+        fileReviewerId: reviewerId,
+      }),
+    ).resolves.toBeUndefined();
+  });
+
+  it("rejects a reviewer from another branch", async () => {
+    const service = createService("branch-1", "branch-2");
+
+    await expect(
+      service.assertMakerReviewerBranchCompatible({
+        fileMakerId: makerId,
+        fileReviewerId: reviewerId,
+      }),
+    ).rejects.toBeInstanceOf(ForbiddenException);
+  });
+
+  it("prefers the immutable case branch snapshot", async () => {
+    const service = createService("old-branch", "branch-2");
+
+    await expect(
+      service.assertMakerReviewerBranchCompatible({
+        fileMakerId: makerId,
+        fileReviewerId: reviewerId,
+        caseBranchId: "branch-2",
+      }),
+    ).resolves.toBeUndefined();
+  });
+});