fusion/packages/dashboard/app/hooks/__tests__/createChatStreamHandlers.test.ts

import { describe, expect, it, vi } from "vitest";
import { createChatStreamHandlers } from "../createChatStreamHandlers";

describe("createChatStreamHandlers", () => {
  it("preserves whitespace across streamed text deltas", () => {
    vi.useFakeTimers();

    let text = "";
    const onDone = vi.fn();
    const onError = vi.fn();
    const cancelStreamingFlushesRef = { current: null } as { current: (() => void) | null };

    const { handlers } = createChatStreamHandlers({
      sessionId: "s-1",
      tempUserMessageId: "temp-1",
      setStreamingText: (value) => {
        text = typeof value === "function" ? value(text) : value;
      },
      setStreamingThinking: vi.fn(),
      setStreamingToolCalls: vi.fn(),
      cancelStreamingFlushesRef,
      onDone,
      onError,
    });

    handlers.onText("Hello.");
    handlers.onText("");
    handlers.onText(" World.");

    vi.advanceTimersToNextTimer();

    expect(text).toBe("Hello. World.");

    handlers.onDone({ messageId: "m-1" });
    expect(onDone).toHaveBeenCalledWith({
      messageId: "m-1",
      message: undefined,
      accumulated: {
        text: "Hello. World.",
        thinking: "",
        toolCalls: [],
        fallbackInfo: undefined,
      },
    });
    expect(onError).not.toHaveBeenCalled();

    vi.useRealTimers();
  });
});