Slack: validate blocks input shape centrally

src/slack/blocks-input.test.ts

@@ -0,0 +1,41 @@
+import { describe, expect, it } from "vitest";
+import { parseSlackBlocksInput } from "./blocks-input.js";
+
+describe("parseSlackBlocksInput", () => {
+  it("returns undefined when blocks are missing", () => {
+    expect(parseSlackBlocksInput(undefined)).toBeUndefined();
+    expect(parseSlackBlocksInput(null)).toBeUndefined();
+  });
+
+  it("accepts blocks arrays", () => {
+    const parsed = parseSlackBlocksInput([{ type: "divider" }]);
+    expect(parsed).toEqual([{ type: "divider" }]);
+  });
+
+  it("accepts JSON blocks strings", () => {
+    const parsed = parseSlackBlocksInput(
+      '[{"type":"section","text":{"type":"mrkdwn","text":"hi"}}]',
+    );
+    expect(parsed).toEqual([{ type: "section", text: { type: "mrkdwn", text: "hi" } }]);
+  });
+
+  it("rejects invalid JSON", () => {
+    expect(() => parseSlackBlocksInput("{bad-json")).toThrow(/valid JSON/i);
+  });
+
+  it("rejects non-array payloads", () => {
+    expect(() => parseSlackBlocksInput({ type: "divider" })).toThrow(/must be an array/i);
+  });
+
+  it("rejects empty arrays", () => {
+    expect(() => parseSlackBlocksInput([])).toThrow(/at least one block/i);
+  });
+
+  it("rejects non-object blocks", () => {
+    expect(() => parseSlackBlocksInput(["not-a-block"])).toThrow(/must be an object/i);
+  });
+
+  it("rejects blocks without type", () => {
+    expect(() => parseSlackBlocksInput([{}])).toThrow(/non-empty string type/i);
+  });
+});