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test(csharp): de-flake FeatureFlagCache single-external-call (assert dedup) #630

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test(csharp): de-flake FeatureFlagCache single-external-call (assert dedup) #630

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14 changes: 12 additions & 2 deletions csharp/test/E2E/FeatureFlagCacheE2ETest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -253,8 +253,18 @@ public async Task TestFeatureFlagCache_SingleExternalCallAcrossConnections()
OutputHelper?.WriteLine(
$"[FeatureFlagCacheE2ETest] {connectionCount} connections to the same host -> actual external feature-flag fetches: {fetchCount}");

// Assert - exactly one external call; the rest served from the shared cache.
Assert.Equal(1, fetchCount);
// Assert - the shared cache DEDUPS: far fewer external fetches than connections.

@peco-review-bot peco-review-bot Bot Aug 5, 2026

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🔵 Low — The <summary> docstring for this test still asserts the old, now-removed contract: it says opening multiple connections "results in exactly one actual connector-service fetch; the rest are served from the cache." The body of the PR deliberately relaxes that to tolerate a second fetch under the negative-cache TTL. The docstring now contradicts the assertion (fetchCount <= 2) directly below it. Consider updating it to describe dedup ("at most 2 fetches") so the stated contract matches the code.

The test method name TestFeatureFlagCache_SingleExternalCallAcrossConnections is similarly stale, but renaming it is optional churn; the docstring is the clearer fix.

(Anchored to the nearest changed line — see the description for the exact location.)

// Not exactly 1: if the first fetch hits a transient failure/timeout, it is cached
// with a short 60s NEGATIVE TTL (FeatureFlagContext.DefaultNegativeTtl) by design, so a
// later connection legitimately re-fetches — a healthy run makes 1 external call, and a
// run that caught one transient makes 2, both of which still prove dedup (4-of-5 or
// 3-of-5 served from cache). Asserting == 1 turned that designed-in retry into a flake
// (observed Expected 1 / Actual 2). Require dedup: strictly fewer fetches than
// connections, and at most 2 (one initial + at most one transient re-fetch).
Assert.True(fetchCount >= 1 && fetchCount < connectionCount && fetchCount <= 2,
$"Feature-flag cache should dedup {connectionCount} connections to at most 2 external "
+ $"fetches (1 healthy, or 2 if the first fetch transiently failed and re-fetched under "
+ $"the negative-cache TTL), but saw {fetchCount}.");
Assert.True(cache.TryGetContext(hostName!, out _), "Context should be cached after the first fetch");
}

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