Labcoat.Testing.NUnit 1.2.2

Labcoat.Testing.NUnit

NUnit support for Labcoat: give each NUnit integration test its own OpenTelemetry trace, so Labcoat can show a View trace / Structured logs link that jumps straight to what the services did during that test in the Aspire dashboard, and stream output live while a test runs. Built on Labcoat.Testing (the framework-neutral core, brought in by this package). For NUnit 4.4 or later (NUnit 5 included) on Microsoft.Testing.Platform (NUnit3TestAdapter 6 or later, <EnableNUnitRunner>true</EnableNUnitRunner>). The library is trim- and AOT-compatible (IsAotCompatible).

Setup: two steps

1. Add the package to the test project. That registers the tracing, no hooks to write: the package adds [assembly: LabcoatTracing] (an NUnit action attribute that wraps every test).

   dotnet add MyApp.Tests package Labcoat.Testing.NUnit
   

2. Call LabcoatTracing.ConfigureAspireTesting(builder) in the fixture that creates the app (for NUnit, the [OneTimeSetUp] of a [SetUpFixture]), after CreateAsync and before BuildAsync. The package can't do this step for you: without it the services the tests start send their telemetry to the testing default (localhost:4317, usually nothing), and the dashboard shows the test's span but none of the services' spans or logs.

   using Labcoat.Testing;
   
   var builder = await DistributedApplicationTestingBuilder.CreateAsync<Projects.MyAppHost>(ct);
   LabcoatTracing.ConfigureAspireTesting(builder);
   var app = await builder.BuildAsync(ct);
   

   A complete fixture: AspireSample.NUnitTests/AspireApp.cs.

Everything is a no-op unless the tests run under Labcoat hosted by an Aspire AppHost (builder.AddLabcoat(...)) with trace collection turned on (off by default: .WithTestTracing(), the Toggle test tracing dashboard command or the toggle in the Labcoat UI). Safe to leave in place for dotnet test and CI.

How it works

NUnit calls the attribute's BeforeTest right before each test's [SetUp] and AfterTest after its [TearDown], on the test's own thread. BeforeTest starts an Activity named after the test (a new trace per test, exported under the test assembly's name) that is current in [SetUp], the test body and [TearDown], so HTTP calls the test makes carry its W3C traceparent and the service spans join the test's trace. It writes labcoat:traceId=<hex> to the test's output (TestContext.Out); Labcoat strips that line and links the test to /traces/detail/<traceId>. AfterTest tags the outcome from NUnit's result (test.outcome, e.g. Passed, Failed:Error, Skipped:Ignored; failures, errors and cancellations get an error status) and ends the span.

The span's test.id is the test node uid Labcoat shows for the row: NUnit3TestAdapter's runner uses the test's fully qualified name (ITest.FullName, e.g. MyApp.Tests.OrderTests.Create(2,"EUR")), so data rows ([TestCase], [TestCaseSource]) and parameterized fixtures each get their own trace and id. With the adapter setting UseParentFQNForParametrizedTests turned on, data rows share one uid in Labcoat; each row still gets its own trace.

Live output

NUnit attaches a test's output to its result only when the test ends, and TestContext.Progress goes to the console without saying which test wrote it (Labcoat then attributes it by timing). LabcoatOutput makes lines appear under the exact test in Labcoat's detail pane while it is still running, and in the test's normal output afterwards:

LabcoatOutput.WriteLine("Starting the Aspire app…");
using var log = LabcoatOutput.CreateWriter(); // a TextWriter (one live line per completed line)

Under Labcoat (LABCOAT_TEST_HOST=1) each line is also written to the process's raw stdout as a labcoat:live: marker tagged with the test's id, class, method and name; outside Labcoat it is just TestContext.Out. No tracing setup is needed for this.

Options

• Only some tests, by category or trait: a trace filter in the Labcoat UI's search syntax (cat:Integration, trait:Kind=Slow, name text). From the AppHost: .WithTestTracing(filter: "cat:Integration") (it wins). As this project's default:

  <LabcoatTracingFilter>cat:Integration</LabcoatTracingFilter>
  

  The adapter passes the test's [Category] and [Property] of the test, its fixture and the assembly as Labcoat shows them, so cat:Integration matches a test marked [Category("Integration")] and trait:Kind=Slow one marked [Property("Kind", "Slow")]. A test that doesn't match gets no span and no trace id. See Trace only some tests.

• Only some classes: set <LabcoatTracingAutoRegister>false</LabcoatTracingAutoRegister> in the test project and put [LabcoatTracing] (optionally with Filter = "...") on the fixtures or methods to trace.

• GenerateAssemblyInfo is false, or the package is referenced through another project: the attribute is not added for you; write [assembly: LabcoatTracing] in the test project.