[test-improver] Add unit tests for DotnetTestConnection.StartServerControlChannelAsync guard conditions

Goal and rationale

DotnetTestConnection.StartServerControlChannelAsync gates the reverse "server control" pipe listener behind a multi-condition guard clause (transport kind, platform, capability negotiation, non-empty pipe name, and idempotency against an already-running listener). Only the Http-transport short-circuit branch had direct coverage (via IsCompatibleProtocolAsync_HttpDoesNotEnableControlPipeAndInvalidFlagsRemainFalse); the remaining three guard combinations on the NamedPipe path were untested, despite being the only thing standing between a benign no-op and either a crash (constructing a NamedPipeClient with an empty pipe name) or silently dropping an in-flight listener task/CancellationTokenSource (if the "already started" guard were ever weakened).

Approach

Added three tests to the existing DotnetTestConnectionTests.cs:

StartServerControlChannelAsync_SupportedButPipeNameEmptyDoesNotCreateListener — capability negotiated but _serverControlPipeName empty → no listener created.
StartServerControlChannelAsync_AlreadyStartedDoesNotReplaceExistingListener — a listener is already running → the call is a no-op and the existing client/task/CTS are left untouched.
StartServerControlChannelAsync_UnsupportedDoesNotCreateListenerDespitePipeName — capability not negotiated despite a present pipe name → no listener created.

Since _serverControlPipeClient's declared type (NamedPipeClient) is [Embedded]-linked separately into the production assembly and this test assembly, a sentinel instance for the "already started" test is constructed via Activator.CreateInstance against the connection's own assembly type rather than new NamedPipeClient(...) (which would be a different, incompatible type at runtime — confirmed by an ArgumentException on the first attempt).

Test Status

Build: 0 warnings, 0 errors (net8.0 + net9.0). dotnet format whitespace --verify-no-changes clean (except the pre-existing, unrelated F# project warning).

Full Microsoft.Testing.Platform.UnitTests suite: 3273 total net8.0 (was 3270), 3274 total net9.0 (was 3270), 0 failed, 22 skipped (pre-existing), no regressions.

Effectiveness evidence

Behavior and inputs	Independent expectation and source	Wrong implementation and distinguishing assertion	Real path and boundary/locale coverage	Evidence
Empty pipe name despite `IsServerControlChannelSupported=true`	Contract: an empty/null `_serverControlPipeName` must short-circuit before constructing a `NamedPipeClient` (which throws `ArgumentException` on an empty pipe name)	Dropping the `RoslynString.IsNullOrEmpty(_serverControlPipeName)` guard term	Real `StartServerControlChannelAsync` entry point, no mocking of the guard itself	Executed red/green
Listener already started (`_serverControlPipeClient` non-null)	Contract: the method must be idempotent — a second call must not replace the existing client/task/CTS	Dropping the `_serverControlPipeClient is not null` guard term	Real entry point; asserts `AreSame` on the pre-existing client/task plus `IsNull` on the CTS (proves no new listener was spun up)	Executed red/green
Capability not negotiated (`IsServerControlChannelSupported=false`) despite a present pipe name	Contract: the capability flag alone must gate listener creation	(not independently faulted this run — distinguishes from the two faulted branches above by construction; flagged for future per-branch mutation if a regression is suspected)	Real entry point	Static/structural (no listener fields set)

Verified via a single temporary production fault (reverted before commit, diff not included in this PR) that simultaneously dropped the empty-pipe-name guard and the already-started guard: exactly 2/3273 tests failed — StartServerControlChannelAsync_SupportedButPipeNameEmptyDoesNotCreateListener (failed with the real ArgumentException from NamedPipeClientStream, proving the empty-pipe-name path is reachable without the guard) and StartServerControlChannelAsync_AlreadyStartedDoesNotReplaceExistingListener (failed the AreSame assertion, proving the idempotency guard is load-bearing). Reverted and reran: 0/3273 failed (net8.0), 0/3274 (net9.0).

Reproducibility

./build.sh -restore
export PATH="$PWD/.dotnet:$PATH"
dotnet build test/UnitTests/Microsoft.Testing.Platform.UnitTests/Microsoft.Testing.Platform.UnitTests.csproj -c Debug -f net8.0
./artifacts/bin/Microsoft.Testing.Platform.UnitTests/Debug/net8.0/Microsoft.Testing.Platform.UnitTests

Note

This was originally intended as a pull request, but the git push operation failed.

Original error: The process '/usr/bin/git' failed with exit code 128

Workflow Run: View run details and download bundle artifact

The bundle file is available in the agent artifact in the workflow run linked above.

Create the pull request manually

# Download the artifact from the workflow run
gh run download '38978556305' -n agent -D '/tmp/agent-38978556305'

# Resolve the bundle source ref, fetch it into a temporary ref, then create the local branch
bundle_path='/tmp/agent-38978556305/aw-test-assist-dotnet-test-connection-control-channel-guards.bundle'
temp_ref='refs/bundles/create-pr-test-assist-dotnet-test-connection-control-channel-guards-3616a442926a603d-f0075ae2'
target_ref='refs/heads/test-assist/dotnet-test-connection-control-channel-guards-3616a442926a603d'
bundle_source_ref=$(git bundle list-heads "$bundle_path" | awk '$2 ~ /^refs\/heads\// { print $2 }')
if [ -z "$bundle_source_ref" ]; then
  bundle_source_ref=$(git bundle list-heads "$bundle_path" | awk '$2 == "HEAD" { print $2 }')
fi
if [ "$(printf '%s\n' "$bundle_source_ref" | sed '/^$/d' | wc -l | tr -d ' ')" != "1" ]; then
  echo "Expected exactly one bundle source ref, found: $bundle_source_ref" >&2
  exit 1
fi
git fetch "$bundle_path" "${bundle_source_ref}:${temp_ref}"
git update-ref "$target_ref" "$temp_ref"
git checkout 'test-assist/dotnet-test-connection-control-channel-guards-3616a442926a603d'
# Ensure the working tree matches the updated branch
git reset --hard
# Remove the temporary bundle ref
git update-ref -d "$temp_ref"

# Push the branch to the target remote
git push 'origin' 'test-assist/dotnet-test-connection-control-channel-guards-3616a442926a603d'

# Create the pull request
gh pr create --title '[test-improver] Add unit tests for DotnetTestConnection.StartServerControlChannelAsync guard conditions' --base 'main' --head 'test-assist/dotnet-test-connection-control-channel-guards-3616a442926a603d' --repo 'microsoft/testfx'

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[test-improver] Add unit tests for DotnetTestConnection.StartServerControlChannelAsync guard conditions #11992

Goal and rationale

Approach

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Effectiveness evidence

Reproducibility

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[test-improver] Add unit tests for DotnetTestConnection.StartServerControlChannelAsync guard conditions #11992

Description

Goal and rationale

Approach

Test Status

Effectiveness evidence

Reproducibility

Activity

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions