fix: resolve type errors across test suite

tests/unit/mergeArrays.test.ts

@@ -0,0 +1,60 @@
+import { describe, test, expect } from "bun:test";
+import { mergeArrays } from "../../src/modules/tools/mergeArrays";
+
+describe("mergeArrays", () => {
+  test("merges two disjoint arrays", () => {
+    const result = mergeArrays([1, 2], [3, 4]);
+    expect(result).toEqual([1, 2, 3, 4]);
+  });
+
+  test("removes duplicates from second array", () => {
+    const result = mergeArrays([1, 2, 3], [2, 3, 4]);
+    expect(result).toEqual([1, 2, 3, 4]);
+  });
+
+  test("handles empty first array", () => {
+    const result = mergeArrays([], [1, 2]);
+    expect(result).toEqual([1, 2]);
+  });
+
+  test("handles empty second array", () => {
+    const result = mergeArrays([1, 2], []);
+    expect(result).toEqual([1, 2]);
+  });
+
+  test("handles both arrays empty", () => {
+    const result = mergeArrays([], []);
+    expect(result).toEqual([]);
+  });
+
+  test("works with strings", () => {
+    const result = mergeArrays(["a", "b"], ["b", "c"]);
+    expect(result).toEqual(["a", "b", "c"]);
+  });
+
+  test("does not mutate original arrays", () => {
+    const a = [1, 2];
+    const b = [2, 3];
+    const result = mergeArrays(a, b);
+    expect(a).toEqual([1, 2]);
+    expect(b).toEqual([2, 3]);
+    expect(result).toEqual([1, 2, 3]);
+  });
+
+  test("accepts custom predicate", () => {
+    const a = [{ id: 1, n: "a" }];
+    const b = [
+      { id: 1, n: "b" },
+      { id: 2, n: "c" },
+    ];
+    const result = mergeArrays(a, b, (x: any, y: any) => x.id === y.id);
+    expect(result).toHaveLength(2);
+    expect(result[0]).toEqual({ id: 1, n: "a" });
+    expect(result[1]).toEqual({ id: 2, n: "c" });
+  });
+
+  test("keeps all elements when predicate never matches", () => {
+    const result = mergeArrays([1, 2], [3, 4], () => false);
+    expect(result).toEqual([1, 2, 3, 4]);
+  });
+});