testing

name	testing
description	Write and run tests for My Network Time — xUnit, fakes, behavioral naming, and project-specific patterns

Testing — My Network Time

Your goal is to help me write, run, and maintain tests that follow the conventions of this project.

Quick commands

# Build everything
dotnet build

# Run all tests
dotnet test tests/MyNetworkTime.Core.Tests/MyNetworkTime.Core.Tests.csproj

# Run tests without rebuilding (faster when code hasn't changed)
dotnet test tests/MyNetworkTime.Core.Tests/MyNetworkTime.Core.Tests.csproj --no-build

In VS Code, use Ctrl+Shift+B for the default build task, or pick from the task list: build-tests, test-core, etc.

Test project layout

tests/MyNetworkTime.Core.Tests/
├── MyNetworkTime.Core.Tests.csproj   # net10.0, xUnit 2.9.x, coverlet
├── ServerSelectionPolicyTests.cs     # [Fact] only, behavioral names
├── SntpClientTests.cs                # async [Fact], ManualTimeProvider + FakeUdpTransport
├── Rfc868ClientTests.cs
├── TimeAdjustmentPolicyTests.cs      # [Fact], TimeAdjustmentAvailability fakes
├── TimeIntervalTests.cs
├── JsonRepositoryTests.cs            # IDisposable for temp-dir cleanup
└── Support/
    ├── ManualTimeProvider.cs         # TimeProvider subclass for deterministic time
    └── FakeTransports.cs             # FakeUdpTransport, FakeTcpTransport

Test conventions (project-specific)

Naming

• Behavioral naming: MethodName_Scenario_ExpectedBehavior
  • ✅ OrderServers_PushesDemotedServersToTheEnd
  • ✅ Evaluate_ReturnsAutoAdjust_WhenModeIsAutomatic_OffsetExceedsThreshold_AndAdjustmentIsAvailable
  • ✅ QueryAsync_ParsesOffsetAndRoundTripFromSntpPacket
• Use [Fact] for unit tests, [Theory] with [InlineData] for data-driven tests.
• No [Trait] attributes — not used in this codebase.

Structure

• Arrange/Act/Assert pattern in every test.
• Test classes are public sealed class.
• Use file-scoped namespaces (namespace MyNetworkTime.Core.Tests;).
• No base test class — use IDisposable for cleanup when needed (see JsonRepositoryTests).
• No IClassFixture or ICollectionFixture — not used here.

Fakes (in tests/MyNetworkTime.Core.Tests/Support/)

• ManualTimeProvider(DateTimeOffset utcNow): Subclass of System.TimeProvider. Provides deterministic UTC time. Call Advance(TimeSpan) to move time forward.
• FakeUdpTransport(Func<...> handler): Implements IUdpTransport. The handler receives (host, port, payload, timeout) and returns a UdpTransportResponse. Exposes LastPayload for assertion.
• FakeTcpTransport(Func<...> handler): Same pattern as FakeUdpTransport but for ITcpTransport.
• When testing protocol clients (SNTP, RFC 868), use ManualTimeProvider + the appropriate fake transport. Do NOT use real network calls.

Assertions

• Use Assert.Equal for value comparisons.
• Use Assert.InRange for time-range assertions (offsets, delays).
• Use Assert.Collection for ordered collection assertions.
• Use Assert.True(File.Exists(...)) for file-system side effects.
• No fluent assertion library — stick to xUnit built-in assertions.

Async tests

• Return async Task (not async void).
• Use await for all async calls — never .Result or .Wait().
• Fake transports return ValueTask.FromResult(...) for synchronous completion.

Data-driven tests

• Use [Theory] + [InlineData] when testing multiple input variations.
• Use AppSettingsDefaults.Create() with { ... } to create settings snapshots with specific overrides — this is the project's pattern for test data.

Cleanup

• If a test creates temp files/directories, implement IDisposable and clean up in Dispose().
• Use Path.Combine(Path.GetTempPath(), $"mynetworktime-tests-{Guid.NewGuid():N}") for temp directories.

When adding a new test

1. Identify the class under test in src/MyNetworkTime.Core/.
2. Create a test class named {ClassName}Tests in tests/MyNetworkTime.Core.Tests/.
3. Determine dependencies: Does it need time? → ManualTimeProvider. Network? → FakeUdpTransport/FakeTcpTransport. File system? → temp directory + IDisposable. Settings? → AppSettingsDefaults.Create() with { ... }.
4. Write the test following Arrange/Act/Assert with behavioral naming.
5. Run: dotnet test tests/MyNetworkTime.Core.Tests/MyNetworkTime.Core.Tests.csproj
6. Verify no regressions: run the full suite before committing.

When changing production code

• If you change behavior in src/MyNetworkTime.Core/, add or update tests in tests/MyNetworkTime.Core.Tests/ in the same commit.
• Run the full test suite after changes — never skip this step.
• If a test fails, fix the test OR the production code — don't leave failing tests.

Anti-patterns (do NOT do these)

• ❌ Real network calls in tests (use fakes)
• ❌ DateTime.Now / DateTimeOffset.Now in tests (use ManualTimeProvider)
• ❌ Task.Delay or Thread.Sleep in tests (use ManualTimeProvider.Advance)
• ❌ Multiple behaviors in one test method
• ❌ Test interdependencies (tests must run in any order)
• ❌ async void test methods (use async Task)
• ❌ Skipping test runs before committing