the serial letter normalization added to the code to normalize the Heh , Ya , Kaf and etc to the correct character

src/utils/plate-normalizer/plate-normalizer.spec.ts

@@ -0,0 +1,131 @@
+import { PlateNormalizerService, normalizePlateText } from "./plate-normalizer.service";
+
+describe("normalizePlateText (pure function)", () => {
+  it("returns unchanged text for a clean plate letter", () => {
+    expect(normalizePlateText("ه")).toBe("ه");
+    expect(normalizePlateText("الف")).toBe("الف");
+  });
+
+  it("strips Zero-Width Joiner (U+200D)", () => {
+    // ه + ZWJ  — the exact scenario from the issue
+    const input = "ه\u200D";
+    expect(normalizePlateText(input)).toBe("ه");
+  });
+
+  it("strips Zero-Width Non-Joiner (U+200C)", () => {
+    expect(normalizePlateText("ه\u200C")).toBe("ه");
+  });
+
+  it("strips Left-to-Right Mark (U+200E)", () => {
+    expect(normalizePlateText("ه\u200E")).toBe("ه");
+  });
+
+  it("strips Right-to-Left Mark (U+200F)", () => {
+    expect(normalizePlateText("ه\u200F")).toBe("ه");
+  });
+
+  it("strips BOM (U+FEFF)", () => {
+    expect(normalizePlateText("\uFEFFه")).toBe("ه");
+  });
+
+  it("converts Arabic ي (U+064A) to Persian ی (U+06CC)", () => {
+    expect(normalizePlateText("\u064A")).toBe("\u06CC");
+  });
+
+  it("does not alter already-Persian ی (U+06CC)", () => {
+    expect(normalizePlateText("\u06CC")).toBe("\u06CC");
+  });
+
+  it("handles a full plate string: 339ه\u200D77 → 339ه77", () => {
+    expect(normalizePlateText("339ه\u200D77")).toBe("339ه77");
+  });
+
+  it("handles multiple invisible chars interleaved", () => {
+    const input = "\u200F339\u200Cه\u200D\uFEFF77\u200E";
+    expect(normalizePlateText(input)).toBe("339ه77");
+  });
+
+  it("trims whitespace", () => {
+    expect(normalizePlateText("  ه  ")).toBe("ه");
+  });
+
+  it("applies NFKC normalization", () => {
+    // Full-width digit ３ (U+FF13) → ASCII 3
+    expect(normalizePlateText("３")).toBe("3");
+  });
+
+  it("returns empty string for empty input", () => {
+    expect(normalizePlateText("")).toBe("");
+  });
+});
+
+describe("PlateNormalizerService", () => {
+  let service: PlateNormalizerService;
+
+  beforeEach(() => {
+    service = new PlateNormalizerService();
+  });
+
+  describe("normalizePlateText", () => {
+    it("delegates to the pure function", () => {
+      expect(service.normalizePlateText("ه\u200D")).toBe("ه");
+    });
+  });
+
+  describe("resolvePlateLetterCode", () => {
+    const PLATE_LETTER_MAP: Record<string, number> = {
+      "\u0627\u0644\u0641": 1, // الف
+      "\u0628": 2,
+      "\u067E": 3,
+      "\u062C": 4,
+      "\u062F": 5,
+      "\u0633": 6,
+      "\u0635": 7,
+      "\u0637": 8,
+      "\u0639": 9,
+      "\u0642": 10,
+      "\u0644": 11,
+      "\u0645": 12,
+      "\u0646": 13,
+      "\u0648": 14,
+      "\u0647": 15, // ه
+      "\u06CC": 16, // ی
+      "\u06A9": 17,
+      "\u0698": 18,
+      "\u062A": 19,
+      "\u062B": 20,
+      "\u0632": 21,
+      "\u0634": 22,
+      "\u0641": 23,
+      "\u06AF": 24,
+    };
+
+    it("returns 15 for clean ه", () => {
+      expect(service.resolvePlateLetterCode("ه", PLATE_LETTER_MAP)).toBe(15);
+    });
+
+    it("returns 15 for ه + ZWJ (the bug scenario)", () => {
+      expect(service.resolvePlateLetterCode("ه\u200D", PLATE_LETTER_MAP)).toBe(
+        15,
+      );
+    });
+
+    it("returns 16 for Arabic ي (mapped to Persian ی)", () => {
+      expect(
+        service.resolvePlateLetterCode("\u064A", PLATE_LETTER_MAP),
+      ).toBe(16);
+    });
+
+    it("returns null for an unknown letter and logs it", () => {
+      const spy = jest.spyOn(
+        (service as any).logger,
+        "debug",
+      );
+      expect(service.resolvePlateLetterCode("؟", PLATE_LETTER_MAP)).toBeNull();
+      expect(spy).toHaveBeenCalledWith(
+        expect.stringContaining("Unknown plate letter"),
+      );
+      spy.mockRestore();
+    });
+  });
+});