Fix FinTS transaction deduplication

convex/bank/fintsMap.test.ts

@@ -0,0 +1,65 @@
+import { describe, expect, test } from "vitest";
+import { mapFinTsTransaction } from "./fintsMap";
+
+const salaryShift = {
+  enabled: true,
+  categoryNames: ["Gehalt & Besoldung"],
+  dayThreshold: 25,
+};
+
+function baseTransaction(overrides: Partial<Parameters<typeof mapFinTsTransaction>[0]> = {}) {
+  return {
+    valueDate: new Date(2026, 5, 22),
+    entryDate: new Date(2026, 5, 22),
+    amount: -12.34,
+    transactionType: "NMSC",
+    bankReference: "",
+    customerReference: "",
+    bookingText: "Kartenzahlung",
+    purpose: "REWE SAGT DANKE",
+    remoteName: "REWE",
+    ...overrides,
+  };
+}
+
+describe("mapFinTsTransaction", () => {
+  test("does not expose MT940 placeholder references as external references", () => {
+    const placeholders = [
+      "NONREF",
+      "NOTPROVIDED",
+      "NOT PROVIDED",
+      "N/A",
+      "POS 13",
+      "POS-42",
+      "POS_1155",
+      "-",
+      "",
+    ];
+
+    for (const placeholder of placeholders) {
+      const mapped = mapFinTsTransaction(
+        baseTransaction({
+          bankReference: placeholder,
+          customerReference: placeholder,
+        }),
+        [],
+        salaryShift,
+      );
+
+      expect(mapped.externalRef).toBeUndefined();
+    }
+  });
+
+  test("keeps real FinTS references for provider-level duplicate detection", () => {
+    const mapped = mapFinTsTransaction(
+      baseTransaction({
+        bankReference: "5J2C21XL0470L56V/39761",
+        customerReference: "NONREF",
+      }),
+      [],
+      salaryShift,
+    );
+
+    expect(mapped.externalRef).toBe("5J2C21XL0470L56V/39761");
+  });
+});