.NET

Applies when your stack uses the .NET SDK (reference project: SDK 10.0.4xx, Microsoft.Testing.Platform as the test runner, xUnit, Testcontainers, a modular monolith).

Gate shape (pattern)

The reference project’s verify.ps1 dotnet lane, in order:

Check the SDK band that global.json pins.
Check that Docker is available, before restore, so failures come fast and clear.
dotnet restore --locked-mode (a stale lock file fails the gate).
dotnet tool restore.
Build in Release with warnings as errors (Directory.Build.props).
Database steps: export the dependency’s changelog, liquibase validate, changelog immutability, a static SQL scan.
Unit, Integration and Architecture tests with coverage.
Merged coverage at 80 % or more of src.

Lanes are chosen by diff. Any uncertainty (no merge base, a dirty tree, an empty diff, a change to the gate itself) runs every lane: a bug in lane selection should cost time, never coverage.

Build servers and memory

MSBuild node reuse leaves idle dotnet.exe workers (a large amount of memory per build set) running after builds, gates and seeds. On a typical workstation this starved Windows and caused out-of-memory failures that were misdiagnosed for a day.
Fix: set MSBUILDDISABLENODEREUSE=1 for every agent shell (Claude Code project settings.json env) and in the gate script. For leftovers from older sessions, run dotnet build-server shutdown when nothing is building. It is graceful and also stops the Roslyn server. Never kill the workers by name.
The test platform’s end-of-run summary printer threw OutOfMemoryException at about 1,000 integration results on a machine with a small fixed page file. Every test had passed. Check the page file and commit limit before blaming the suite.

Microsoft.Testing.Platform traps

Run dotnet test from inside the clone. global.json’s test.runner: Microsoft.Testing.Platform is found from the working directory. Outside the clone, dotnet falls back to VSTest and rejects --project with MSB1001: Unknown switch. It looks like a broken SDK, but it’s only the folder.
dotnet test -- -namespace ... silently runs zero tests with this runner. Use --filter-class or --filter-method. A trailing * works, but a * in the middle matches nothing, so list the classes. A filtered run that reports 0 tests ran nothing.
Targeted runs: dotnet test --project tests/Integration/Tests.Integration.csproj -c Release --no-build --output Detailed --filter-class <Full.Class.Name>. Keep the output in a file named in the progress log. A flake once couldn’t be identified because its output was dropped.

Test isolation

Each integration folder is one xUnit collection with its own cloned database from a template. Collections run in parallel, and classes within one run in order.
Class order differs between build paths (the checkout, a scratch clone, each gate clone), but is stable within one. A test that depends on rows other classes commit can pass every targeted run and fail in one gate. Reproduce by running the folder from a second path.
Dispose every DbContext a test builds (await using). Undisposed fixture contexts leaked pooled connections past PostgreSQL’s default 100 (53300). The reference project raised the test container to max_connections=500, printed the peak in every gate, and treats a peak above 400 as a follow-up.
A test that alters an object a host’s startup check reads starts the host first. Otherwise it passes when another test happened to start the host and fails when it runs first in its class. Its fail check is the test run alone.
The unit project’s gate checks read configuration and test-support files as text. A change there runs the whole unit project, even when “nothing it compiles changed.”
Slow tests that guard rare, stable failures (startup refusal, which takes tens of seconds) carry a SignOff trait. Normal gates leave them out, and phase sweeps and batches touching that code include them.

Fail checks

Restore a probed file with git checkout -- <file>, not a copy. A copy keeps the backup’s old modification time, so the next incremental build skips the compile and runs the probed code: a false fail or pass. If a copy was used, touch the file.
Batch all fail-check probes into one scripted pass: break, run the filter, restore, confirm clean, for every probe.

Modules

The reference project enforced module boundaries with architecture tests:

Each module is <Module>.Contracts plus <Module>, and references another module only through .Contracts.
Hosts hold no business logic.
Each module derives its own DbContext from a shared base, registered through one helper that sets the provider, the pool cap and a rotating credential source.

See postgresql.md for the database side.