Joseph Doherty
99 lines
4.3 KiB
C#
99 lines
4.3 KiB
C#
using Shouldly;
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using Xunit;
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using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
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namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests;
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/// <summary>
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/// Covers <see cref="ConnectionBackoff"/> — the shared capped-exponential backoff extracted
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/// from the S7 poll fork (05/STAB-8; the seam plan R2-01 wires into the S7 connect throttle).
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/// Two surfaces: the static <see cref="ConnectionBackoff.ComputeDelay"/> schedule and the
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/// per-device attempt-throttle instance.
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/// </summary>
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[Trait("Category", "Unit")]
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public sealed class ConnectionBackoffTests
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{
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private static readonly TimeSpan Base = TimeSpan.FromSeconds(1);
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private static readonly TimeSpan Cap = TimeSpan.FromSeconds(30);
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/// <summary>Zero (or negative) consecutive failures returns the base interval unchanged.</summary>
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[Theory]
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[InlineData(0)]
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[InlineData(-1)]
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public void ComputeDelay_NoFailures_ReturnsBaseInterval(int failures)
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=> ConnectionBackoff.ComputeDelay(Base, failures, Cap).ShouldBe(Base);
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/// <summary>The delay doubles per consecutive failure (1×, 2×, 4×, 8×) until it saturates the cap.</summary>
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[Theory]
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[InlineData(1, 1)]
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[InlineData(2, 2)]
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[InlineData(3, 4)]
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[InlineData(4, 8)]
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[InlineData(5, 16)]
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public void ComputeDelay_DoublesPerFailure(int failures, int expectedSeconds)
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=> ConnectionBackoff.ComputeDelay(Base, failures, Cap)
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.ShouldBe(TimeSpan.FromSeconds(expectedSeconds));
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/// <summary>Growth saturates at the cap and never exceeds it, even at a large failure count (overflow guard).</summary>
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[Theory]
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[InlineData(6)] // 32s would exceed 30s cap
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[InlineData(30)]
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[InlineData(1000)] // shift saturates; ticks overflow guard returns cap
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public void ComputeDelay_SaturatesAtCap(int failures)
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=> ConnectionBackoff.ComputeDelay(Base, failures, Cap).ShouldBe(Cap);
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/// <summary>A fresh throttle permits the first attempt immediately.</summary>
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[Fact]
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public void ShouldAttempt_FreshInstance_AllowsImmediately()
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{
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var backoff = new ConnectionBackoff(Base, Cap);
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backoff.ShouldAttempt(DateTime.UtcNow).ShouldBeTrue();
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}
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/// <summary>After a failure the throttle blocks inside the backoff window and reopens once it elapses.</summary>
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[Fact]
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public void RecordFailure_BlocksWithinWindow_ReopensAfter()
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{
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var backoff = new ConnectionBackoff(Base, Cap);
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var t0 = new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc);
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backoff.RecordFailure(t0); // window = 1s (first failure)
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backoff.ShouldAttempt(t0).ShouldBeFalse(); // still inside window
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backoff.ShouldAttempt(t0.AddMilliseconds(500)).ShouldBeFalse();
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backoff.ShouldAttempt(t0.AddSeconds(1)).ShouldBeTrue(); // window elapsed
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}
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/// <summary>Consecutive failures widen the window (1s then 2s).</summary>
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[Fact]
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public void RecordFailure_ConsecutiveFailures_WidenWindow()
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{
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var backoff = new ConnectionBackoff(Base, Cap);
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var t0 = new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc);
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backoff.RecordFailure(t0); // 1s
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backoff.RecordFailure(t0.AddSeconds(1)); // 2nd failure → 2s window
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backoff.ShouldAttempt(t0.AddSeconds(2)).ShouldBeFalse(); // within the 2s window
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backoff.ShouldAttempt(t0.AddSeconds(3)).ShouldBeTrue();
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}
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/// <summary>Success resets immediately — recovery is never delayed by a residual window.</summary>
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[Fact]
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public void RecordSuccess_ResetsWindowImmediately()
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{
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var backoff = new ConnectionBackoff(Base, Cap);
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var t0 = new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc);
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backoff.RecordFailure(t0);
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backoff.RecordFailure(t0); // deep in a widened window
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backoff.ShouldAttempt(t0).ShouldBeFalse();
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backoff.RecordSuccess();
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backoff.ShouldAttempt(t0).ShouldBeTrue(); // reset, no residual delay
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// And the schedule restarts from the base window on the next failure.
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backoff.RecordFailure(t0);
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backoff.ShouldAttempt(t0.AddMilliseconds(999)).ShouldBeFalse();
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backoff.ShouldAttempt(t0.AddSeconds(1)).ShouldBeTrue();
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}
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}
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