Add unit tests for common/array files (#23006)

* add vitest coverage

* Add js doc to functions

* Add tests for common/array

test/common/array/ensure-array.test.ts

@@ -0,0 +1,28 @@
+import { describe, expect, it } from "vitest";
+import { ensureArray } from "../../../src/common/array/ensure-array";
+
+describe("ensureArray", () => {
+  it("should return undefined when input is undefined", () => {
+    expect(ensureArray(undefined)).toBeUndefined();
+  });
+
+  it("should return the same array when input is an array", () => {
+    const arr = [1, 2, 3];
+    expect(ensureArray(arr)).toBe(arr);
+  });
+
+  it("should wrap non-array value in an array", () => {
+    const value = 5;
+    expect(ensureArray(value)).toEqual([value]);
+  });
+
+  it("should wrap non-array object in an array", () => {
+    const value = { key: "value" };
+    expect(ensureArray(value)).toEqual([value]);
+  });
+
+  it("should return the same readonly array when input is a readonly array", () => {
+    const arr = [1, 2, 3] as const;
+    expect(ensureArray(arr)).toBe(arr);
+  });
+});