fix(esg): short-TTL definition cache for central lookups (review 2026-10-21 05/P2)

2026-10-22 08:41:54 -04:00
parent ee8be8001e
commit 12f815a7ea
8 changed files with 193 additions and 4 deletions
@@ -0,0 +1,55 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.ExternalSystems;
+
+namespace ZB.MOM.WW.ScadaBridge.ExternalSystemGateway.Tests;
+
+/// <summary>Tests for <see cref="ExternalDefinitionLookupCache"/> (review 2026-10-21 05/P2).</summary>
+public class ExternalDefinitionLookupCacheTests
+{
+    private static ExternalSystemDefinition Sys() => new("S", "https://x", "none") { Id = 1 };
+
+    /// <summary>Verifies hits within the TTL skip the repository and expiry refetches.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task Hit_WithinTtl_SkipsFetch_AndExpiryRefetches()
+    {
+        var time = new FakeTimeProvider(DateTimeOffset.UtcNow);
+        var cache = new ExternalDefinitionLookupCache(TimeSpan.FromSeconds(5), time);
+        var fetches = 0;
+        Task<ExternalSystemDefinition?> Fetch() { fetches++; return Task.FromResult<ExternalSystemDefinition?>(Sys()); }
+
+        await cache.GetSystemAsync("S", Fetch);
+        await cache.GetSystemAsync("S", Fetch);
+        Assert.Equal(1, fetches);
+
+        time.Advance(TimeSpan.FromSeconds(6));
+        await cache.GetSystemAsync("S", Fetch);
+        Assert.Equal(2, fetches);
+    }
+
+    /// <summary>Verifies misses are not cached and a zero TTL disables caching.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task NotFound_IsNotCached_AndZeroTtlDisables()
+    {
+        var cache = new ExternalDefinitionLookupCache(TimeSpan.FromSeconds(5));
+        var fetches = 0;
+        Task<ExternalSystemDefinition?> Miss() { fetches++; return Task.FromResult<ExternalSystemDefinition?>(null); }
+        await cache.GetSystemAsync("S", Miss);
+        await cache.GetSystemAsync("S", Miss);
+        Assert.Equal(2, fetches);
+
+        var off = new ExternalDefinitionLookupCache(TimeSpan.Zero);
+        fetches = 0;
+        Task<ExternalSystemDefinition?> Hit() { fetches++; return Task.FromResult<ExternalSystemDefinition?>(Sys()); }
+        await off.GetSystemAsync("S", Hit);
+        await off.GetSystemAsync("S", Hit);
+        Assert.Equal(2, fetches);
+    }
+
+    private sealed class FakeTimeProvider(DateTimeOffset start) : TimeProvider
+    {
+        private DateTimeOffset _now = start;
+        public override DateTimeOffset GetUtcNow() => _now;
+        public void Advance(TimeSpan by) => _now += by;
+    }
+}