test(utils): add unit tests for chunkItems

zenglingbiao · zenglingbiao · commit 2948e6101b8b · 2026-07-01T00:36:35.000+08:00
Add 8 test cases covering fixed-size array splitting, empty input,
size &lt;= 0, size=1, size &gt; length, exact division, readonly input
preservation, and fractional size behavior.
diff --git a/src/utils/chunk-items.test.ts b/src/utils/chunk-items.test.ts
@@ -0,0 +1,51 @@
+// Chunk items tests cover fixed-size array splitting edge cases.
+import { describe, expect, it } from "vitest";
+import { chunkItems } from "./chunk-items.js";
+
+describe("chunkItems", () => {
+  it("splits items into fixed-size chunks", () => {
+    expect(chunkItems([1, 2, 3, 4, 5], 2)).toEqual([[1, 2], [3, 4], [5]]);
+    expect(chunkItems(["a", "b", "c", "d"], 3)).toEqual([["a", "b", "c"], ["d"]]);
+  });
+
+  it("returns a single chunk when size is 0 or negative", () => {
+    expect(chunkItems([1, 2, 3], 0)).toEqual([[1, 2, 3]]);
+    expect(chunkItems([1, 2, 3], -1)).toEqual([[1, 2, 3]]);
+  });
+
+  it("returns empty array for empty input", () => {
+    expect(chunkItems([], 5)).toEqual([]);
+    expect(chunkItems([], 0)).toEqual([[]]);
+    expect(chunkItems([], -1)).toEqual([[]]);
+  });
+
+  it("wraps each item when size is 1", () => {
+    expect(chunkItems([1, 2, 3], 1)).toEqual([[1], [2], [3]]);
+  });
+
+  it("returns a single chunk when size exceeds array length", () => {
+    expect(chunkItems([1, 2, 3], 10)).toEqual([[1, 2, 3]]);
+  });
+
+  it("exactly divides when size matches array length", () => {
+    expect(chunkItems([1, 2, 3], 3)).toEqual([[1, 2, 3]]);
+  });
+
+  it("preserves readonly input without mutation", () => {
+    const input: readonly number[] = [10, 20, 30, 40];
+    const result = chunkItems(input, 2);
+    expect(result).toEqual([
+      [10, 20],
+      [30, 40],
+    ]);
+    expect(input).toEqual([10, 20, 30, 40]);
+  });
+
+  it("handles fractional size using slice native truncation behavior", () => {
+    // slice() truncates non-integer args, so 2.5 → chunk boundaries at 0, 2.5, 5.0
+    expect(chunkItems([1, 2, 3, 4, 5], 2.5)).toEqual([
+      [1, 2],
+      [3, 4, 5],
+    ]);
+  });
+});
