test: remove redundant frontend checks

src/pages/account-income/model/display.test.ts

@@ -44,6 +44,71 @@ function summary(currency: string, coupon: string, dividend: string) {
 	};
 }
 
+describe("income membership validation", () => {
+	const entry: IncomeAnalytics["entries"][number] = {
+		accruedInterest: null,
+		category: "income",
+		commission: null,
+		description: "Купон",
+		figi: "FIGI",
+		id: "coupon-1",
+		instrumentKey: "income-group",
+		instrumentType: "bond",
+		instrumentUid: null,
+		logoName: null,
+		occurredAt: "2026-08-01T12:00:00Z",
+		payment: money("RUB", "10"),
+		price: null,
+		quantity: null,
+		ticker: "BOND",
+		type: "OPERATION_TYPE_COUPON",
+	};
+
+	const instrument: IncomeAnalytics["instruments"][number] = {
+		...summary("RUB", "10", "0"),
+		displayName: "BOND",
+		figi: "FIGI",
+		instrumentType: "bond",
+		instrumentUid: null,
+		key: entry.instrumentKey,
+		receiptCount: 1,
+		ticker: "BOND",
+	};
+
+	const valid: IncomeAnalytics = {
+		...analytics,
+		entries: [entry],
+		instruments: [instrument],
+		totalsByCurrency: [summary("RUB", "10", "0")],
+	};
+
+	it.each([
+		["missing key", undefined],
+		["empty key", ""],
+		["whitespace key", "  "],
+		["non-string key", 12],
+		["unknown key", "not-in-breakdown"],
+	])("rejects an entry with %s", (_name, instrumentKey) => {
+		// Deliberately malformed API data exercises the runtime validation boundary.
+		const response = {
+			...valid,
+			entries: [{ ...entry, instrumentKey }],
+		} as unknown as IncomeAnalytics;
+
+		expect(toIncomeDisplayModel(response)).toBeNull();
+	});
+
+	it.each([
+		["duplicate instrument keys", { instruments: [instrument, instrument] }],
+		["currency mismatch", { entries: [{ ...entry, payment: money("USD", "10") }] }],
+		["receipt count mismatch", { instruments: [{ ...instrument, receiptCount: 2 }] }],
+		["missing entries", { entries: [] }],
+		["empty instrument key", { instruments: [{ ...instrument, key: "" }] }],
+	])("rejects %s", (_name, invalid) => {
+		expect(toIncomeDisplayModel({ ...valid, ...invalid })).toBeNull();
+	});
+});
+
 describe("income comparison display", () => {
 	it.each([
 		["25", "100", "+25 %"],