diff --git a/packages/auth/src/application/use-cases/sign-in.use-case.test.ts b/packages/auth/src/application/use-cases/sign-in.use-case.test.ts
index ca5388e..32bbc74 100644
--- a/packages/auth/src/application/use-cases/sign-in.use-case.test.ts
+++ b/packages/auth/src/application/use-cases/sign-in.use-case.test.ts
@@ -1,4 +1,5 @@
 import { describe, it, expect } from "vitest";
+import { ZodError } from "zod";
 import { signInUseCase, signInOutputSchema } from "@/application/use-cases/sign-in.use-case";
 import { MockUsersRepository } from "@/infrastructure/repositories/users.repository.mock";
 import { MockAuthenticationService } from "@/infrastructure/services/authentication.service.mock";
@@ -60,7 +61,7 @@ describe("signInUseCase output validation (R25)", () => {
     } as unknown as IAuthenticationService;
 
     const useCase = signInUseCase(users, auth);
-    await expect(useCase({ username: "alice", password: "x" })).rejects.toThrow(/parse|invalid/i);
+    await expect(useCase({ username: "alice", password: "x" })).rejects.toBeInstanceOf(ZodError);
   });
 
   it("exports an output schema that mirrors the success shape", () => {
diff --git a/packages/auth/src/application/use-cases/sign-up.use-case.test.ts b/packages/auth/src/application/use-cases/sign-up.use-case.test.ts
index c3d62a4..c2a32ff 100644
--- a/packages/auth/src/application/use-cases/sign-up.use-case.test.ts
+++ b/packages/auth/src/application/use-cases/sign-up.use-case.test.ts
@@ -1,4 +1,5 @@
 import { describe, it, expect } from "vitest";
+import { ZodError } from "zod";
 import { signUpUseCase, signUpOutputSchema } from "@/application/use-cases/sign-up.use-case";
 import { MockUsersRepository } from "@/infrastructure/repositories/users.repository.mock";
 import { MockAuthenticationService } from "@/infrastructure/services/authentication.service.mock";
@@ -48,7 +49,7 @@ describe("signUpUseCase output validation (R25)", () => {
     const useCase = signUpUseCase(users, auth);
     await expect(
       useCase({ username: "carol", password: "secret_password", confirmPassword: "secret_password" }),
-    ).rejects.toThrow(/parse|invalid/i);
+    ).rejects.toBeInstanceOf(ZodError);
   });
 
   it("exports an output schema that mirrors the success shape", () => {
diff --git a/packages/auth/src/interface-adapters/controllers/sign-in.controller.test.ts b/packages/auth/src/interface-adapters/controllers/sign-in.controller.test.ts
index 0816eb5..b72ada3 100644
--- a/packages/auth/src/interface-adapters/controllers/sign-in.controller.test.ts
+++ b/packages/auth/src/interface-adapters/controllers/sign-in.controller.test.ts
@@ -20,8 +20,7 @@ describe("signInController", () => {
       username: "alice",
       password: "testpassword",
     });
-    expect(result).toBeDefined();
-    expect(result.name).toBeTruthy();
+    expect(result.name).toBe("session");
     expect(result.value).toBeTruthy();
   });