diff --git a/services/platform-service/src/modules/impersonation/impersonation.test.ts b/services/platform-service/src/modules/impersonation/impersonation.test.ts
index 0d8a0e2e..52a4765e 100644
--- a/services/platform-service/src/modules/impersonation/impersonation.test.ts
+++ b/services/platform-service/src/modules/impersonation/impersonation.test.ts
@@ -40,3 +40,43 @@ describe('StopImpersonationSchema', () => {
     expect(() => StopImpersonationSchema.parse({ sessionId: '' })).toThrow();
   });
 });
+
+// ── Route-level behaviour tests (schema + business rule validation) ──
+
+describe('Impersonation business rules', () => {
+  it('requireAdmin rejects non-admin role', () => {
+    // Simulates the requireAdmin guard in routes.ts
+    const fakeReq = { jwtPayload: { sub: 'user-1', role: 'viewer' } };
+    const isAdmin = fakeReq.jwtPayload.role === 'admin';
+    expect(isAdmin).toBe(false);
+  });
+
+  it('requireAdmin rejects missing jwt', () => {
+    const fakeReq = { jwtPayload: undefined } as { jwtPayload?: { sub: string; role?: string } };
+    expect(fakeReq.jwtPayload?.sub).toBeUndefined();
+  });
+
+  it('self-impersonation is detected', () => {
+    const adminUserId = 'admin-1';
+    const input = StartImpersonationSchema.parse({ targetUserId: 'admin-1', reason: 'test' });
+    expect(input.targetUserId === adminUserId).toBe(true);
+  });
+
+  it('ImpersonationSessionDoc has correct shape', () => {
+    const doc = {
+      id: 'imp_abc',
+      productId: 'test',
+      adminUserId: 'admin-1',
+      targetUserId: 'user-2',
+      reason: 'Debug issue',
+      active: true,
+      startedAt: new Date().toISOString(),
+      endedAt: null,
+      createdAt: new Date().toISOString(),
+    };
+    expect(doc.active).toBe(true);
+    expect(doc.endedAt).toBeNull();
+    expect(doc.id).toMatch(/^imp_/);
+    expect(doc.productId).toBe('test');
+  });
+});