fix(driver-s7): resolve Low code-review findings (Driver.S7-003,005,009,010,013)
- Driver.S7-003: ArgumentNullException.ThrowIfNull on the references argument at the top of ReadAsync / WriteAsync (was reaching .Count before any null check). - Driver.S7-005: drop the redundant global::S7.Net.Plc qualifiers in ReadOneAsync / WriteOneAsync — using S7.Net already covers Plc. - Driver.S7-009: PollLoopAsync degrades _health to Degraded after sustained failure and backs off exponentially up to PollBackoffCap; resets on a healthy tick so an operator can see the loop wedge. - Driver.S7-010: Dispose runs the synchronous teardown directly with a bounded WhenAll Wait drain instead of bridging via DisposeAsync(). - Driver.S7-013: reject unsupported S7DataType values (Int64 / UInt64 / Float64 / String / DateTime) at InitializeAsync so half-implemented types no longer leak BadNotSupported live nodes into the address space. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Joseph Doherty
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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.Driver.S7.Tests;
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/// <summary>
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/// Regression tests for the remaining code-review findings closed against the S7 driver:
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/// Driver.S7-003 (Read/WriteAsync null-arg validation), Driver.S7-009 (poll-loop health
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/// update + backoff), Driver.S7-010 (Dispose without sync-over-async), and Driver.S7-013
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/// (reject not-yet-implemented S7DataType values at init).
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/// </summary>
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[Trait("Category", "Unit")]
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public sealed class S7DriverCodeReviewFixTests2
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{
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// ── Driver.S7-003 — Read/WriteAsync must throw ArgumentNullException, not NRE ─────────
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[Fact]
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public async Task ReadAsync_with_null_fullReferences_throws_ArgumentNullException()
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{
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// The driver must validate its inputs consistently with DiscoverAsync (which already
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// uses ArgumentNullException.ThrowIfNull). A NullReferenceException escaping the entry
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// point bypasses the gate and gives the caller a non-actionable stack.
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using var drv = new S7Driver(new S7DriverOptions { Host = "192.0.2.1" }, "s7-null-read");
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await Should.ThrowAsync<ArgumentNullException>(async () =>
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await drv.ReadAsync(null!, TestContext.Current.CancellationToken));
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}
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[Fact]
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public async Task WriteAsync_with_null_writes_throws_ArgumentNullException()
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{
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using var drv = new S7Driver(new S7DriverOptions { Host = "192.0.2.1" }, "s7-null-write");
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await Should.ThrowAsync<ArgumentNullException>(async () =>
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await drv.WriteAsync(null!, TestContext.Current.CancellationToken));
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}
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// ── Driver.S7-009 — Poll loop must update health on sustained failure ────────────────
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[Fact]
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public async Task PollLoop_against_uninitialized_driver_degrades_health()
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{
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// Subscribing without InitializeAsync means RequirePlc() throws on every poll tick.
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// Previously the empty catch swallowed everything and the dashboard reported Healthy
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// / Unknown indefinitely. With the fix the poll loop must surface the failure on the
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// health surface so an operator can see it (driver-stability convention).
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var opts = new S7DriverOptions
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{
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Host = "192.0.2.1",
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Probe = new S7ProbeOptions { Enabled = false },
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};
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var drv = new S7Driver(opts, "s7-poll-health");
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await drv.SubscribeAsync(["A"], TimeSpan.FromMilliseconds(50), TestContext.Current.CancellationToken);
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// Wait long enough for several poll ticks. With backoff the second tick should arrive
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// within ~100-200 ms; allow generous slack.
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for (var i = 0; i < 40 && drv.GetHealth().State is DriverState.Unknown or DriverState.Initializing; i++)
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await Task.Delay(50, TestContext.Current.CancellationToken);
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drv.GetHealth().State.ShouldBe(DriverState.Degraded,
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"sustained poll failure must surface on the health state — see Driver.S7-009");
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await drv.ShutdownAsync(CancellationToken.None);
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await drv.DisposeAsync();
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}
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[Fact]
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public async Task PollLoop_applies_capped_backoff_after_consecutive_failures()
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{
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// After repeated poll errors the loop must back off rather than burn CPU re-polling
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// every Interval — Driver.S7-009 calls for a capped backoff. Inspect the ratio of
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// observed tick count to the floor count we would have seen WITHOUT backoff over a
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// short window. Without backoff, an Interval=50 ms loop with sub-ms ReadAsync
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// RequirePlc-throw would tick ~20 times in 1 s. With capped backoff it ticks far
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// fewer; we use a generous upper bound that still proves "something is throttling".
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var opts = new S7DriverOptions
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{
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Host = "192.0.2.1",
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Probe = new S7ProbeOptions { Enabled = false },
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};
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var drv = new S7Driver(opts, "s7-poll-backoff");
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var ticks = 0;
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drv.OnDataChange += (_, _) => Interlocked.Increment(ref ticks);
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await drv.SubscribeAsync(["A"], TimeSpan.FromMilliseconds(50), TestContext.Current.CancellationToken);
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// OnDataChange is never raised (every poll fails) so we can't count via the event.
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// Instead, time-bound the test and rely on the health-degradation test above to prove
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// the catch ran; here we just confirm the driver doesn't deadlock or spin so hot it
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// refuses to shut down. ShutdownAsync must complete within the drain window.
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await Task.Delay(500, TestContext.Current.CancellationToken);
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var sw = System.Diagnostics.Stopwatch.StartNew();
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await drv.ShutdownAsync(CancellationToken.None);
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sw.Stop();
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sw.Elapsed.ShouldBeLessThan(TimeSpan.FromSeconds(6),
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"shutdown must complete inside the drain timeout — a runaway backoff would block it");
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await drv.DisposeAsync();
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_ = ticks; // silence unused
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}
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// ── Driver.S7-010 — Dispose() must not deadlock via sync-over-async ──────────────────
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[Fact]
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public void Dispose_completes_synchronously_without_sync_over_async_round_trip()
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{
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// The sync Dispose() path must perform the teardown directly rather than blocking on
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// DisposeAsync().AsTask().GetAwaiter().GetResult(). The current sync-over-async pattern
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// is a known deadlock risk even when the wrapped Task.Run paths happen to be safe.
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// We assert by measuring Dispose() runtime on a no-subscription, no-init driver: it
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// should complete in microseconds, not the ~5 s drain window that a hung sync-over-async
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// would burn waiting on a never-completing continuation.
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var drv = new S7Driver(new S7DriverOptions { Host = "192.0.2.1" }, "s7-dispose-sync");
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var sw = System.Diagnostics.Stopwatch.StartNew();
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drv.Dispose();
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sw.Stop();
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sw.Elapsed.ShouldBeLessThan(TimeSpan.FromSeconds(1),
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"Dispose() must teardown directly — see Driver.S7-010");
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}
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[Fact]
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public void Dispose_is_idempotent()
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{
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// After the rewrite Dispose() must remain safe to call twice — disposal is
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// best-effort and the second call must not throw.
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var drv = new S7Driver(new S7DriverOptions { Host = "192.0.2.1" }, "s7-dispose-twice");
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drv.Dispose();
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Should.NotThrow(() => drv.Dispose());
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}
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// ── Driver.S7-013 — Reject not-yet-implemented S7DataType values at init ─────────────
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[Theory]
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[InlineData(S7DataType.Int64)]
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[InlineData(S7DataType.UInt64)]
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[InlineData(S7DataType.Float64)]
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[InlineData(S7DataType.String)]
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[InlineData(S7DataType.DateTime)]
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public async Task Initialize_rejects_not_yet_implemented_data_type_with_NotSupportedException(S7DataType dt)
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{
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// A tag declared with one of the not-yet-wired data types parses cleanly and creates
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// an OPC UA node via DiscoverAsync — then every Read/Write of it returns BadNotSupported.
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// The half-implemented type must be rejected at init so a site can't deploy a config
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// that produces dead nodes (Driver.S7-013).
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var opts = new S7DriverOptions
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{
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Host = "192.0.2.1",
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Timeout = TimeSpan.FromMilliseconds(250),
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// Use a DB.DBD address — the parser accepts it for every data type. The init guard
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// must fault on the data-type rather than on the address.
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Tags = [new S7TagDefinition("X", "DB1.DBD0", dt)],
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};
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using var drv = new S7Driver(opts, $"s7-bad-dt-{dt}");
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var ex = await Should.ThrowAsync<NotSupportedException>(async () =>
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await drv.InitializeAsync("{}", TestContext.Current.CancellationToken));
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ex.Message.ShouldContain(dt.ToString());
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var health = drv.GetHealth();
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health.State.ShouldBe(DriverState.Faulted);
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}
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[Theory]
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[InlineData(S7DataType.Bool, "DB1.DBX0.0")]
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[InlineData(S7DataType.Byte, "DB1.DBB0")]
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[InlineData(S7DataType.Int16, "DB1.DBW0")]
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[InlineData(S7DataType.UInt16, "DB1.DBW0")]
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[InlineData(S7DataType.Int32, "DB1.DBD0")]
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[InlineData(S7DataType.UInt32, "DB1.DBD0")]
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[InlineData(S7DataType.Float32, "DB1.DBD0")]
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public async Task Initialize_accepts_implemented_data_types(S7DataType dt, string addr)
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{
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// Sanity check the guard is targeted — implemented data types must still pass. The
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// TCP connect still fails (reserved host); the failure must NOT be a NotSupportedException
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// from the data-type guard.
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var opts = new S7DriverOptions
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{
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Host = "192.0.2.1",
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Timeout = TimeSpan.FromMilliseconds(250),
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Tags = [new S7TagDefinition("X", addr, dt)],
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};
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using var drv = new S7Driver(opts, $"s7-good-dt-{dt}");
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var ex = await Should.ThrowAsync<Exception>(async () =>
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await drv.InitializeAsync("{}", TestContext.Current.CancellationToken));
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ex.ShouldNotBeOfType<NotSupportedException>(
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"implemented data types must pass the init guard — the failure must be the connect");
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}
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}
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