阶段3（上）：Python/asyncio/FastAPI 专题的课程、企业场景、面试题和可运行示例

topics/python/asyncio/examples/fanout/test_fanout.py

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+import asyncio
+import time
+
+from fanout import RetryableError, fake_llm, fan_out
+
+
+def run(coro):
+    return asyncio.run(coro)
+
+
+def test_concurrency_limit():
+    active, peak = 0, 0
+
+    def job():
+        async def call():
+            nonlocal active, peak
+            active += 1
+            peak = max(peak, active)
+            await asyncio.sleep(0.05)
+            active -= 1
+            return "ok"
+        return call
+
+    res = run(fan_out({str(i): job() for i in range(10)}, concurrency=3, timeout=1))
+    assert peak == 3 and all(r.value == "ok" for r in res)
+
+
+def test_retry_then_success():
+    [r] = run(fan_out({"a": fake_llm("a", 0.01, fail_times=1)}, concurrency=1, timeout=1, retries=1))
+    assert r.value == "a 的回答" and r.attempts == 2
+
+
+def test_partial_failure():
+    async def boom():
+        raise ValueError("参数错误")  # 不可重试的错误：只尝试一次
+
+    res = run(fan_out({"ok": fake_llm("ok", 0.01), "bad": boom, "slow": fake_llm("slow", 1)},
+                      concurrency=3, timeout=0.1, retries=1))
+    by = {r.key: r for r in res}
+    assert by["ok"].value == "ok 的回答"
+    assert by["bad"].error == "ValueError: 参数错误"
+    assert by["slow"].error == "TimeoutError"
+
+
+def test_retry_exhausted():
+    [r] = run(fan_out({"x": fake_llm("x", 0.01, fail_times=5)}, concurrency=1, timeout=1, retries=2))
+    assert r.value is None and "RetryableError" in r.error
+
+
+def test_overall_deadline_cancels():
+    start = time.perf_counter()
+    res = run(fan_out({"fast": fake_llm("fast", 0.01), "slow": fake_llm("slow", 5)},
+                      concurrency=2, timeout=10, deadline=0.2))
+    assert time.perf_counter() - start < 1
+    by = {r.key: r for r in res}
+    assert by["fast"].value and by["slow"].error == "整体超时，已取消"
+
+
+def test_retryable_error_is_exception():
+    assert issubclass(RetryableError, Exception)