Microsoft.Extensions.Diagnostics.Testing 9.4.0

Microsoft.Extensions.Diagnostics.Testing

Hand-crafted fakes to make telemetry-related testing easier.

Install the package

From the command-line:

dotnet add package Microsoft.Extensions.Diagnostics.Testing

Or directly in the C# project file:

<ItemGroup>
  <PackageReference Include="Microsoft.Extensions.Diagnostics.Testing" Version="[CURRENTVERSION]" />
</ItemGroup>

Usage Example

Fake logging

These components enable faking logging services for testing purposes.

When using this package, you can register a fake logging provider by one of the following methods:

public static ILoggingBuilder AddFakeLogging(this ILoggingBuilder builder)
public static ILoggingBuilder AddFakeLogging(this ILoggingBuilder builder, IConfigurationSection section)
public static ILoggingBuilder AddFakeLogging(this ILoggingBuilder builder, Action<FakeLogCollectorOptions> configure)

You can also register fake logging in the service collection:

public static IServiceCollection AddFakeLogging(this IServiceCollection services)
public static IServiceCollection AddFakeLogging(this IServiceCollection services, IConfigurationSection section)
public static IServiceCollection AddFakeLogging(this IServiceCollection services, Action<FakeLogCollectorOptions> configure)

After registering the fake logging services, you can resolve the fake logging provider with this method:

public static FakeLogCollector GetFakeLogCollector(this IServiceProvider services)

You can also create an instance of FakeLogger using one of its constructors:

public FakeLogger(FakeLogCollector? collector = null, string? category = null)
public FakeLogger(Action<string> outputSink, string? category = null)

You can then use it right away, for example:

var fakeLogger = new FakeLogger<MyComponent>();

// Optionally, you can set the log level
// fakeLogger.ControlLevel(LogLevel.Debug, enabled: true);

var myComponentUnderTest = new MyComponent(fakeLogger);
myComponentUnderTest.DoWork(); // We assume that the component will produce some logs

FakeLogCollector collector = fakeLogger.Collector; // Collector allows you to access the captured logs
IReadOnlyList<FakeLogRecord> logs = collector.GetSnapshot();
// ... assert that the logs are correct

Metric collector

The MetricCollector allows you to collect metrics in tests. It has a few constructors and you can choose the one that fits your needs:

public MetricCollector(Instrument<T> instrument, TimeProvider? timeProvider = null)
public MetricCollector(ObservableInstrument<T> instrument, TimeProvider? timeProvider = null)
public MetricCollector(object? meterScope, string meterName, string instrumentName, TimeProvider? timeProvider = null)
public MetricCollector(Meter meter, string instrumentName, TimeProvider? timeProvider = null)

When you have an exact instrument, you can use the first two constructors. If you have a meter scope (typically it's IMeterFactory), you can use the third constructor. If you have a meter, use the last one.

Here is an example of how to use the MetricCollector:

using System.Diagnostics.Metrics;
using Microsoft.Extensions.Diagnostics.Testing;

using var meter = new Meter("TestMeter");
using var collector = new MetricCollector<int>(meter, "TestInstrument");

var myComponentUnderTest = new MyComponent(meter);
myComponentUnderTest.DoWork(); // We assume that the component will produce some integer metrics

CollectedMeasurement<int>? measurement = collector.LastMeasurement();
// ... assert that the measurement is correct

Please note that the MetricCollector is generic and you need to specify the type of the metric you want to collect (e.g. int, double, etc.).

Feedback & Contributing

We welcome feedback and contributions in our GitHub repo.