added api logic, vitest, minimal testing ui

api/tests/variable-categories.guard.test.ts

@@ -0,0 +1,56 @@
+// tests/variable-categories.guard.test.ts
+import request from "supertest";
+import { describe, it, expect, beforeEach, beforeAll, afterAll } from "vitest";
+import appFactory from "./appFactory";
+import { prisma, resetUser, ensureUser, U, cid, closePrisma } from "./helpers";
+import type { FastifyInstance } from "fastify";
+
+let app: FastifyInstance;
+
+beforeAll(async () => {
+  app = await appFactory();
+});
+
+afterAll(async () => {
+  await app.close();
+  await closePrisma();
+});
+
+describe("Variable Categories guard (sum=100)", () => {
+  beforeEach(async () => {
+    await resetUser(U);
+    await ensureUser(U);
+
+    await prisma.variableCategory.createMany({
+      data: [
+        { id: cid("a"), userId: U, name: "A", percent: 50, priority: 1, isSavings: false, balanceCents: 0n },
+        { id: cid("b"), userId: U, name: "B", percent: 50, priority: 2, isSavings: false, balanceCents: 0n },
+      ],
+    });
+  });
+
+  afterAll(async () => {
+    await closePrisma();
+  });
+
+  it("rejects create that would push sum away from 100", async () => {
+    const res = await request(app.server)
+      .post("/variable-categories")
+      .set("x-user-id", U)
+      .send({ name: "Oops", percent: 10, isSavings: false, priority: 99 });
+
+    expect(res.statusCode).toBe(400);
+    expect(res.body?.message).toMatch(/Percents must sum to 100/i);
+  });
+
+  it("rejects update that breaks the sum", async () => {
+    const existing = await prisma.variableCategory.findFirst({ where: { userId: U } });
+    const res = await request(app.server)
+      .patch(`/variable-categories/${existing!.id}`)
+      .set("x-user-id", U)
+      .send({ percent: 90 });
+
+    expect(res.statusCode).toBe(400);
+    expect(res.body?.message).toMatch(/Percents must sum to 100/i);
+  });
+});