added api logic, vitest, minimal testing ui

api/tests/allocator.test.ts

@@ -0,0 +1,65 @@
+// tests/allocator.test.ts
+import { describe, it, expect, beforeEach, afterAll } from "vitest";
+import { prisma, resetUser, ensureUser, U, cid, pid, closePrisma } from "./helpers";
+import { allocateIncome } from "../src/allocator";
+
+describe("allocator — core behaviors", () => {
+  beforeEach(async () => {
+    await resetUser(U);
+    await ensureUser(U);
+  });
+
+  afterAll(async () => {
+    await closePrisma();
+  });
+
+  it("distributes remainder to variables by largest remainder with savings-first tie", async () => {
+    const c1 = cid("c1");
+    const c2 = cid("c2"); // make this savings to test the tiebreaker
+    await prisma.variableCategory.createMany({
+      data: [
+        { id: c1, userId: U, name: "Groceries", percent: 60, priority: 2, isSavings: false, balanceCents: 0n },
+        { id: c2, userId: U, name: "Saver",     percent: 40, priority: 1, isSavings: true,  balanceCents: 0n },
+      ],
+    });
+
+    const p1 = pid("rent");
+    await prisma.fixedPlan.create({
+      data: {
+        id: p1,
+        userId: U,
+        name: "Rent",
+        cycleStart: new Date().toISOString(),
+        dueOn: new Date(Date.now() + 7 * 864e5).toISOString(),
+        totalCents: 10000n,
+        fundedCents: 0n,
+        priority: 1,
+        fundingMode: "auto-on-deposit",
+      },
+    });
+
+    // $100 income
+    const result = await allocateIncome(prisma as any, U, 10000, new Date().toISOString(), "inc1");
+    expect(result).toBeDefined();
+    // rent should be funded first up to need
+    const fixed = result.fixedAllocations ?? [];
+    const variable = result.variableAllocations ?? [];
+
+    // sanity
+    expect(Array.isArray(fixed)).toBe(true);
+    expect(Array.isArray(variable)).toBe(true);
+  });
+
+  it("handles zeros and single bucket", async () => {
+    const cOnly = cid("only");
+    await prisma.variableCategory.create({
+      data: { id: cOnly, userId: U, name: "Only", percent: 100, priority: 1, isSavings: false, balanceCents: 0n },
+    });
+
+    const result = await allocateIncome(prisma as any, U, 0, new Date().toISOString(), "inc2");
+    expect(result).toBeDefined();
+    const variable = result.variableAllocations ?? [];
+    const sum = variable.reduce((s, a: any) => s + (a.amountCents ?? 0), 0);
+    expect(sum).toBe(0);
+  });
+});