lc-testkit 0.18.0

Testing harness for langchainrust — record real LLM exchanges and replay them offline
Documentation 
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//! RecordingProvider → JSONL → ReplayProvider 往返:同一响应一致。
//!
//! 这是 harness 的核心闭环:真调一次落盘,再从文件回放得到相同结果。

mod common;

use common::FakeModel;
use lc_core::language_models::BaseChatModel;
use lc_core::tools::ToolDefinition;
use lc_schema::Message;
use lc_testkit::{RecordingProvider, ReplayProvider};

#[tokio::test]
async fn record_then_replay_roundtrip() {
    let dir = tempfile::tempdir().unwrap();
    let path = dir.path().join("capture.jsonl");

    // 1. 真调一次(假模型),响应写入录制文件
    let recorded =
        RecordingProvider::new(FakeModel::new("Rust 是一门系统编程语言。"), &path).unwrap();
    let result = recorded
        .chat(
            vec![Message::system("测试"), Message::human("什么是 Rust?")],
            None,
        )
        .await
        .unwrap();
    assert_eq!(result.content, "Rust 是一门系统编程语言。");

    // 2. 文件恰好 1 行合法 JSONL
    let raw = std::fs::read_to_string(&path).unwrap();
    assert_eq!(raw.lines().count(), 1);

    // 3. 从文件回放:内容与 token 计数一致
    let replay = ReplayProvider::from_file(&path).unwrap();
    assert_eq!(replay.len(), 1);

    let replayed = replay
        .chat(vec![Message::human("什么是 Rust?")], None)
        .await
        .unwrap();
    assert_eq!(replayed.content, result.content);
    assert_eq!(replayed.model, result.model);
    // 假模型的 token 计数是确定的:2 条消息输入 / 1 输出 / 3 总计
    let tokens = replayed.token_usage.as_ref().expect("回放应带 token 计数");
    assert_eq!(tokens.prompt_tokens, 2);
    assert_eq!(tokens.completion_tokens, 1);
    assert_eq!(tokens.total_tokens, 3);
}

#[tokio::test]
async fn record_with_bound_tools_then_replay() {
    let dir = tempfile::tempdir().unwrap();
    let path = dir.path().join("tools.jsonl");

    // 1. 绑定工具后录制:exchange 的 tools 字段应落盘
    let recorded = RecordingProvider::new(FakeModel::new("计算结果是 5。"), &path).unwrap();
    let bound = recorded.bind_tools(vec![ToolDefinition::new("calculator", "数学计算")]);
    let result = bound
        .chat(vec![Message::system("测试"), Message::human("2+3=?")], None)
        .await
        .unwrap();
    assert_eq!(result.content, "计算结果是 5。");

    // 2. 文件里应有工具名
    let raw = std::fs::read_to_string(&path).unwrap();
    assert!(
        raw.contains("calculator"),
        "录播文件应包含绑定的工具名: {raw}"
    );

    // 3. 回放:tools 保留,响应一致
    let replay = ReplayProvider::from_file(&path).unwrap();
    assert_eq!(replay.len(), 1);
    let replayed = replay
        .chat(vec![Message::human("2+3=?")], None)
        .await
        .unwrap();
    assert_eq!(replayed.content, result.content);
}

#[test]
fn old_fixture_without_tools_still_deserializes() {
    // 旧格式 fixture(llm_chain_f01.jsonl)没有 tools 字段 → 读成 None,零改动。
    let line = r#"{"messages":[{"content":"q","type":"human"}],"response":{"content":"a","model":"m","token_usage":{"prompt_tokens":1,"completion_tokens":1,"total_tokens":2}}}"#;
    let exchange: lc_testkit::RecordedExchange = serde_json::from_str(line).unwrap();
    assert!(exchange.tools.is_none());
}