Instruction file imported from microsoft/VirtualClient (.github/instructions/testing.instructions.md). Copyright stays with the author.

Unit Testing Patterns

Framework and Attributes

• NUnit 3 with [TestFixture], [Test], [SetUp], [OneTimeSetUp]
• Moq for mocking interfaces
• AutoFixture via MockFixture base class
• Required: [Category("Unit")] or [Category("Functional")] — tests without a category are silently skipped by CI (build-test.sh filters on Category=Unit)

Test Class Structure

• Test classes must inherit MockFixture (from VirtualClient.TestFramework)
• Class name: {ComponentName}Tests (e.g., FioExecutorTests)
• Method names: Descriptive with underscores (e.g., FioExecutorSelectsTheExpectedDisks_RemoteDiskScenario)

[TestFixture]
[Category("Unit")]
public class FioExecutorTests : MockFixture
{
    private IDictionary<string, IConvertible> profileParameters;
    private string mockResults;

    [OneTimeSetUp]
    public void SetupFixture()
    {
        this.mockResults = MockFixture.ReadFile(MockFixture.ExamplesDirectory, "FIO", "Results_FIO.json");
    }

    [SetUp]
    public void SetupTest()
    {
        this.Setup(PlatformID.Unix);
        this.ProcessManager.OnCreateProcess = (command, arguments, workingDir) =>
        {
            return new InMemoryProcess
            {
                OnHasExited = () => true,
                ExitCode = 0,
                StartInfo = new ProcessStartInfo { FileName = command, Arguments = arguments },
                StandardOutput = new ConcurrentBuffer(new StringBuilder(this.mockResults))
            };
        };
    }

    [Test]
    public void FioExecutorSelectsTheExpectedDisksForTest_RemoteDiskScenario()
    {
        // Arrange, Act, Assert
    }
}

MockFixture Provides

• Pre-configured mocks: ApiClient, DiskManager, FileSystem, File, Directory, ProcessManager
• Setup(PlatformID platform, Architecture arch) — configure platform-specific behavior
• MockFixture.ReadFile(...) — load example output from Examples/ directories
• Test doubles: InMemoryProcess, InMemoryFile, InMemoryDirectory

Parser Tests

• Load real example output from Examples/ directories (not inline strings)
• Run the parser against actual benchmark output
• Assert specific metric names, values, and units:

[Test]
public void MyParserParsesMetricsCorrectly()
{
    string output = MockFixture.ReadFile(MockFixture.ExamplesDirectory, "MyWorkload", "results.txt");
    MyWorkloadMetricsParser parser = new MyWorkloadMetricsParser(output);
    IList<Metric> metrics = parser.Parse();

    Assert.IsNotEmpty(metrics);
    MetricAssert.Exists(metrics, "throughput", 12345.67, MetricUnit.OperationsPerSec);
    MetricAssert.Exists(metrics, "latency_p99", 1.23, MetricUnit.Milliseconds);
}

Process Mocking

Use InMemoryProcess via ProcessManager.OnCreateProcess:

• Set ExitCode, OnHasExited, StandardOutput, StandardError
• StandardOutput uses ConcurrentBuffer(new StringBuilder(content))