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TenantGuard

0018. Test libraries beyond xUnit

  • Status: Accepted
  • Date: 2026-11-01

Context

Section titled “Context”

Tests used xUnit v3, Microsoft.EntityFrameworkCore.Sqlite, Microsoft.CodeAnalysis.CSharp.Analyzer.Testing and the ASP.NET Core shared framework, so assertions were xUnit’s Assert.* and fakes were written by hand. The maintainer asked to assert with AwesomeAssertions and to evaluate NSubstitute, Bogus, AutoFixture, AutoFixture.AutoNSubstitute, FsCheck and Verify.MSTest, and to write the integration tests with LightBDD.

Decision

Section titled “Decision”

All test-only; xUnit stays the test framework:

  • AwesomeAssertions (Apache-2.0, the community fork of FluentAssertions 7) in every test project, through tests/Directory.Build.props with a global using. Assert.Throws<T> became ThrowExactly<T>, keeping the exact-type check, and Assert.Equal on a sequence became the ordered Equal.
  • FsCheck property tests where a rule holds for every input: blank tenant property names and bypass reasons are rejected, names and reasons are kept as given, and the probe converts any tenant string into a string or Guid tenant property, or fails naming both.
  • NSubstitute for Finbuckle’s tenant context accessor in tests/e2e. LogCapture stays hand-written: substituting ILogger.Log<TState> with its formatter reads worse.
  • Verify.XunitV3, not Verify.MSTest, which needs MSTest. It snapshots the probe’s failure table. Verify charges a maintenance fee and fails the build without a declaration: the test kit’s test project claims the OpenSource exemption until 2027-11.
  • Bogus (MIT) for a rule nothing tested before: exceptions and logs name tenant ids and key values and no other entity value. NoValueLeakTests fills every other value through Bogus with fixed seeds, makes each kind of cross-tenant write and checks the exceptions and logs; a probe test does the same for the report.
  • LightBDD (BSD-2-Clause) for the integration tests, as Given/When/Then steps. LightBDD.XUnit3 3.12.1 throws a TypeLoadException on xunit.v3 4 (LightBDD#409), and the test platform then drops every [Scenario] test without reporting it, so scenarios run from [Fact] through Runner.RunScenarioAsync, and task lint:scenarios fails on [Scenario].
  • NetArchTest.eNhancedEdition (MIT) in tests/architecture/, turning dependency, namespace, exception, immutability and interceptor rules into tests.
  • AutoFixture and AutoFixture.AutoNSubstitute are not used: each test’s EF model is the point of the test, so anonymous objects have nothing to fill.

Consequences

Section titled “Consequences”
  • Renew Verify’s exemption before 2027-11, or the build fails.
  • When LightBDD supports xunit.v3 4, switch to [Scenario] and drop lint:scenarios.
  • The testing strategy says which library a new test uses.