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Retarget the MTP client onto Microsoft.Testing.Platform.ServerClient.Source - #16300

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Retarget the MTP client onto Microsoft.Testing.Platform.ServerClient.Source#16300
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@nohwnd nohwnd commented Jul 21, 2026

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What this does

vstest hand-maintained an MTP (Microsoft.Testing.Platform) server-mode JSON-RPC client under
src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/. testfx now ships that client as a source-only
package, Microsoft.Testing.Platform.ServerClient.Source, built from the MTP server's own protocol and
serialization source, so the wire format cannot drift from the server.

This deletes vstest's transport core and retargets the glue onto the package's IMtpServerClient:

  • Deleted: MtpServerConnection, MtpJson, MtpConstants, MtpClientHelpers.
  • Retargeted: MtpProxyDiscoveryManager, MtpProxyExecutionManager, MtpTestNodeConverter — launch via
    MtpServerClient.Launch, drive InitializeAsync/DiscoverTestsAsync/RunTestsAsync/ExitAsync, read
    node updates from the TestNodesUpdated event with typed MtpTestNodeUpdate accessors, and bridge
    EqtTrace through DelegateMtpClientLogger.
  • Added: MtpClientOptionsFactory — builds MtpServerClientOptions and maps server log levels.
  • Unchanged: MtpProxyManagerFactory, MtpDataCollectionForwarder (transport-agnostic).

The package is a compile-time source dependency (PrivateAssets="all"): it compiles into
Microsoft.TestPlatform.CrossPlatEngine.dll with no shipped DLL, no runtime dependency, and no new
public API.

Do not merge — this is a draft

The package is not on any public or dnceng feed yet. It is introduced by microsoft/testfx#10085, which
is an unmerged draft. This PR references an interim local feed committed under eng/local-mtp-feed
(NuGet.config, eng/Versions.props, and the PackageReference each carry an INTERIM comment). CI
cannot restore the package from a public feed, so the build cannot go green here. Merge is blocked on
testfx publishing the package. Remove eng/local-mtp-feed and revert the NuGet.config source once it
ships.

Build status against the current package drop

The current drop (2.4.0-dev.numberfix, uniquely named to avoid NuGet same-version cache
collisions while it is served from the committed local feed) builds CrossPlatEngine clean on all three
TFMs (net462, netstandard2.0, net8.0) with zero warnings under TreatWarningsAsErrors and the public-API
analyzers, and adds no public API. Earlier package build blockers (public types leaking as public API,
missing per-file usings, missing down-level polyfills) are resolved in this drop.

Local validation

MtpUnderVstestTests runs on both console axes (7 methods each), 12/14 pass:

  • .NET runner (CrossPlatEngine net8, System.Text.Json): 7/7 pass. With the number-decode fix in the
    current package drop, every test on this axis passes — discovery, execution, per-test standard output,
    run-settings environment-variable injection, an out-of-proc data collector, blame, a mixed classic+MTP
    run, and a single-TRX run. This axis was 0/7 before the fix (see "Resolved" below), so it is the
    end-to-end proof that the retarget drives the real System.Text.Json client correctly.
  • .NET Framework runner (CrossPlatEngine net462, Jsonite): 5/7 pass. Same scenarios, all passing
    except 2 /logger:trx tests. Those 2 fail to load the TRX logger in my locally-built net462 runner,
    at logger argument-processing, before the MTP client runs — a pre-existing local-deployment issue, not
    the retarget. Proof: the same two test methods pass on the .NET runner, and a classic (non-MTP) trx test
    fails identically on this runner. The source package is compile-only and adds no runtime assembly, so it
    cannot be the cause.

A test-infrastructure fix is included: mixing the interim local-folder feed with the remote https feeds
in the acceptance-test dotnet restore made NuGet mis-root the relative local path and mis-normalize the
https URLs (NU1301). GetNugetSourceParameters now resolves local sources to absolute paths and orders
remote feeds first. This is only needed while the package lives on the interim local feed.

Resolved questions (confirmed by the package owner against server + client source)

  • G1 — the normalized Node shape is now a documented contract. Both formatter paths (Jsonite on
    net462/netstandard2.0, System.Text.Json on .NET) materialize the graph the same way: every JSON object
    becomes IDictionary<string, object?>, every array ICollection<object>, strings/bools/null as-is.
    Numbers are boxed per formatter (int/long/double), so numerics must be coerced, never hard-cast. vstest
    reads standardOutput, standardError, location.file, location.line-start, traits, and the
    vstest.* bridge properties from the raw Node dictionary by string key; MtpTestNodeConverter coerces
    the numeric ones (TryGetRawInt handles int/long/double/float/decimal), so it is robust to the
    per-formatter boxing.
  • G2 — ordering guarantee, confirmed and documented on IMtpServerClient. Once
    DiscoverTestsAsync/RunTestsAsync completes, every TestNodesUpdated handler has already run. This is
    what lets vstest drop its old completion-sentinel drain.
  • G3 — uid-only run filter, confirmed. The server projects node.Uid alone when building the run
    filter and never reads DisplayName, so sending the uid as the identity is correct.
  • G4 — artifacts come from the run response. MtpRunResult.Artifacts is the complete, authoritative
    set (absolute file path, producer uid, type, display name, description), mapped to AttachmentSet. The
    AttachmentsReceived event is not additive on this request/response path (it fires only on the separate
    push-only protocol), so there is no double counting. Validated by the passing data-collector and blame
    tests on the net462 axis.
  • G5 — MtpServerClientOptions.EnvironmentVariables is keyed ordinal. vstest's classic path folds
    environment-variable keys case-insensitively on Windows. This PR keys both of vstest's own
    environment-variable collection dictionaries the same way (commit 5ceda8598) so case-variant keys
    collapse before the values reach the ordinal package dictionary, preserving the classic Windows behavior.

Resolved: the package's STJ number decode

The .NET axis was previously red because the package's compiled-in System.Text.Json deserializer called
JsonElement.GetInt32() on every JSON number, which threw FormatException on the non-Int32 numbers
(durations, timestamps) in real test-node notifications. The Jsonite path (net462) decodes numbers
generically, which is why only the .NET axis was affected. Original runtime stack:

MTP client read loop failed: System.FormatException: One of the identified items was in an invalid format.
   at System.Text.Json.JsonElement.GetInt32()
   at ...Json.<RegisterDefaultDeserializers>b__0_5(...) in ServerMode/JsonRpc/Json/Json.Deserializers.cs:line 55
   at ...JsonElementDeserializer`1.CreateObject(...)
   at ...Json.Bind[T](...) Json.cs:line 102   (recurses via Json.Deserializers.cs L64/L106/L151)
   at ...FormatterUtilities.MessageFormatter.Deserialize[T](...) FormatterUtilities.cs:line 87

The package owner fixed it upstream (testfx#10085): the two untyped number sinks now decode generically
(ReadNumber: TryGetInt32TryGetInt64TryGetUInt64double), a pure superset — anything that
fits Int32 still boxes as int, so nothing that worked before regresses. This PR consumes that fixed
drop, and the .NET axis went from 0/7 to 7/7 with no vstest-side change. It stays draft only until the
package reaches a restorable feed.

🤖

…Source

testfx now ships vstest's MTP server-mode JSON-RPC client as a source-only
package built from the MTP server's own protocol and serialization source, so
the wire format cannot drift from the server.

Delete vstest's transport core (MtpServerConnection, MtpJson, MtpConstants,
MtpClientHelpers) and retarget the glue onto the package's IMtpServerClient:
launch via MtpServerClient.Launch, drive Initialize/Discover/Run/Exit, read
node updates from the TestNodesUpdated event with typed MtpTestNodeUpdate
accessors, and bridge EqtTrace through DelegateMtpClientLogger.
MtpClientOptionsFactory centralizes option construction and log-level mapping.

The package is a compile-time source dependency (PrivateAssets=all), so no
runtime dependency and no public API are added.

Blocked on testfx publishing the package (microsoft/testfx#10085); references
an interim local feed, so CI cannot restore it yet.
Copilot AI review requested due to automatic review settings July 21, 2026 09:06

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Pull request overview

This PR retargets vstest’s Microsoft.Testing.Platform (MTP) server-mode JSON-RPC client integration in CrossPlatEngine from a hand-maintained transport implementation to the new source-only Microsoft.Testing.Platform.ServerClient.Source package, aiming to prevent protocol/serialization drift from the server.

Changes:

  • Added a source-only PackageReference to compile the MTP server client into Microsoft.TestPlatform.CrossPlatEngine.dll.
  • Updated MTP discovery/execution proxies and node conversion to use MtpServerClient APIs and typed MtpTestNodeUpdate updates.
  • Removed the legacy in-repo transport/protocol helpers (MtpServerConnection, MtpJson, MtpConstants, MtpClientHelpers) and introduced MtpClientOptionsFactory.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file
File Description
src/Microsoft.TestPlatform.CrossPlatEngine/Microsoft.TestPlatform.CrossPlatEngine.csproj Adds source-only package reference for the new MTP server client.
src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpTestNodeConverter.cs Converts typed MTP node updates into vstest TestCase/TestResult and reads remaining fields from the raw property bag.
src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpServerConnection.cs Deletes legacy TCP/LSP-framed JSON-RPC transport implementation.
src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpProxyExecutionManager.cs Switches execution path to MtpServerClient (launch/init/run/exit) and consumes typed node updates + artifacts.
src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpProxyDiscoveryManager.cs Switches discovery path to MtpServerClient (launch/init/discover/exit) and consumes typed node updates.
src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpJson.cs Deletes legacy Jsonite-based JSON access helpers.
src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpConstants.cs Deletes legacy protocol constants (method names, keys, state values).
src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpClientOptionsFactory.cs Adds options/logger glue for launching the MTP client and mapping log levels to vstest.
src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpClientHelpers.cs Deletes legacy helpers for init params, completion sentinel, and node enumeration.
NuGet.config Adds an interim local package source for restoring the unshipped source-only package.
eng/Versions.props Adds interim version property for Microsoft.Testing.Platform.ServerClient.Source.

Comment thread NuGet.config
Comment on lines 7 to 12
<clear />
<!-- INTERIM local feed for the unshipped source-only MTP client package
(Microsoft.Testing.Platform.ServerClient.Source). This is a machine-local path and will not
resolve in CI. Remove once the package ships to a public feed via microsoft/testfx#10085. -->
<add key="local-mtp" value="Q:\q\local-mtp-feed" />
<!--Begin: Package sources managed by Dependency Flow automation. Do not edit the sources below.-->
Comment on lines +25 to +27
<!-- Source-only MTP server-mode JSON-RPC client: compiled into this assembly (no shipped DLL, no
runtime dependency, no new public API). INTERIM: restored from a local feed until
microsoft/testfx#10085 ships Microsoft.Testing.Platform.ServerClient.Source publicly. -->
NuGet.config pointed local-mtp at the absolute path Q:\q\local-mtp-feed, which
is machine-local and does not exist in CI, so restore failed with an incorrect
path. Move the feed under the repo at eng/local-mtp-feed, point NuGet.config at
that repo-relative path, and commit the package into the feed. .gitignore keeps
ignoring *.nupkg but adds a negation for eng/local-mtp-feed/*.nupkg so the feed
package is tracked.

The package is the fresh Design-A drop of
Microsoft.Testing.Platform.ServerClient.Source 2.4.0-dev, which builds
CrossPlatEngine clean on net462, netstandard2.0, and net8.0 (0 errors, 0
warnings) with the retargeted glue. Interim only; remove the feed once
microsoft/testfx#10085 ships the package to a public feed.

🤖
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Pull request overview

Copilot reviewed 11 out of 13 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

NuGet.config:12

  • Adding a repo-local package source (eng/local-mtp-feed) plus checking in the .nupkg makes restores depend on committed binary artifacts and can mask updates from real feeds (the same version from a remote feed would still prefer the local copy). Before this PR is mergeable, this interim feed should be removed and restore should come from an authenticated/public feed.
    <clear />
    <!-- INTERIM committed local feed for the unshipped source-only MTP client package
         (Microsoft.Testing.Platform.ServerClient.Source). Repo-relative so it resolves on every
         machine and in CI. Remove once the package ships to a public feed via microsoft/testfx#10085. -->
    <add key="local-mtp" value="eng/local-mtp-feed" />
    <!--Begin: Package sources managed by Dependency Flow automation. Do not edit the sources below.-->

Comment on lines +175 to +186
private static bool TryGetRawInt(MtpTestNodeUpdate update, string key, out int result)
{
switch (update.Node.TryGetValue(key, out object? value) ? value : null)
{
case int i: result = i; return true;
case long l: result = unchecked((int)l); return true;
case double d: result = (int)d; return true;
case float f: result = (int)f; return true;
case decimal m: result = (int)m; return true;
default: result = 0; return false;
}
}
…restore

The acceptance tests restore the TestAssets solution, which transitively
restores product projects like CrossPlatEngine that now reference the interim
local-mtp feed. Passing that local-folder feed to dotnet restore alongside the
remote https feeds triggered two NuGet quirks, both surfacing as NU1301: a
relative --source path is rooted at each restored project's directory, and a
local-folder source placed before the remote sources mis-normalizes the https
URLs into per-project relative paths.

Resolve relative local-folder sources to absolute paths and emit the remote
sources first so all local-folder sources come last; remote feeds keep their
configured order. Only needed while the MTP client package lives on the interim
local feed, and harmless once testfx#10085 ships it to a public feed.

🤖
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Pull request overview

Copilot reviewed 12 out of 14 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (2)

src/Microsoft.TestPlatform.CrossPlatEngine/Microsoft.TestPlatform.CrossPlatEngine.csproj:28

  • The comment says the source-only package adds "no new public API", but source-embedded code can introduce public types into CrossPlatEngine if the package sources declare them as public. It would be safer to phrase this as an intended property contingent on the package keeping its types internal, to avoid misleading future readers (and to align with PublicApiAnalyzers expectations).
    <!-- Source-only MTP server-mode JSON-RPC client: compiled into this assembly (no shipped DLL, no
         runtime dependency, no new public API). INTERIM: restored from a local feed until
         microsoft/testfx#10085 ships Microsoft.Testing.Platform.ServerClient.Source publicly. -->
    <PackageReference Include="Microsoft.Testing.Platform.ServerClient.Source" Version="$(MicrosoftTestingPlatformServerClientSourceVersion)" PrivateAssets="all" />

src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpTestNodeConverter.cs:183

  • TryGetRawInt uses unchecked casts from long/double/float/decimal to int. If the server sends a large value (or a negative one), this can wrap and produce an invalid TestCase.LineNumber. Since this is parsing untrusted wire data, it should range-check and reject values outside 0..int.MaxValue.
            case int i: result = i; return true;
            case long l: result = unchecked((int)l); return true;
            case double d: result = (int)d; return true;
            case float f: result = (int)f; return true;
            case decimal m: result = (int)m; return true;

Comment on lines +510 to +517
// Guard against both: resolve relative local-folder sources to absolute paths, and emit the remote
// sources first so all local-folder sources come last. Remote sources (containing "://") keep their
// configured order and pass through unchanged.
var remote = sources.Where(s => s.Contains("://"));
var local = sources
.Where(s => !s.Contains("://"))
.Select(s => Path.IsPathRooted(s) ? s : Path.GetFullPath(Path.Combine(root, s)));
var feeds = remote.Concat(local).ToList();
connection.SendNotification(MtpConstants.ExitMethod, null);
return connection.ProcessId;
CollectAttachments(runResult, attachments);
client.ExitAsync(_cancellationTokenSource.Token).GetAwaiter().GetResult();
}

connection.SendNotification(MtpConstants.ExitMethod, null);
client.ExitAsync(_cancellationTokenSource.Token).GetAwaiter().GetResult();
Both places that collect environment variables for the MTP application
launch now share one comparer: case-insensitive on Windows, case-sensitive
elsewhere. Before, the runsettings path used that comparer but the
data-collector-only path used a plain ordinal dictionary, so a run with no
runsettings variables but with data-collector variables lost the
case-folding the classic testhost path applied on Windows. The package
options dictionary is ordinal, so deduping here preserves the classic
Windows semantics before the values reach it.

🤖
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Pull request overview

Copilot reviewed 12 out of 14 changed files in this pull request and generated no new comments.

Replaces the interim 2.4.0-dev pack with the official drop that fixes the
STJ number-decode bug: untyped JSON numbers were hard-cast to Int32, so node
bags carrying doubles (durations) or longs (timestamps) threw FormatException
and faulted the MTP read loop on the net8 client. The fix decodes numbers
generically (ReadNumber: TryGetInt32 -> TryGetInt64 -> TryGetUInt64 -> double).

Pinned to the unique version 2.4.0-dev.20260721161520 to avoid NuGet
same-version cache collisions while the package is served from the committed
local feed.

MtpUnderVstestTests: net11.0 (STJ) axis now 7/7 (was 0/7); net481 (Jsonite)
axis 5/7. The 2 remaining failures are a pre-existing net462 TRX-logger load
issue that also breaks classic non-MTP trx tests, unrelated to this retarget.

🤖
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Pull request overview

Copilot reviewed 12 out of 14 changed files in this pull request and generated no new comments.

… drop

Swaps the interim feed pack and pin from the timestamped unique
2.4.0-dev.20260721161520 to the coordinator's canonical uniquely-named drop
2.4.0-dev.numberfix (MD5 FC7F7A9F68EF482718B61DC9DA5F38B4). Byte-equivalent
fixed content -- the packed net8 Json.Deserializers.cs decodes untyped JSON
numbers via ReadNumber at both sinks (L55/L97, helper L344), same as the prior
drop -- this only adopts the stable canonical interim identity the package
owner is standardizing on across consumers.

Validation unchanged: MtpUnderVstestTests net11.0 (STJ) axis 7/7, full suite
12/14 (the 2 remaining failures are the pre-existing net462 TRX-logger load
issue, unrelated to this retarget).

🤖
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Pull request overview

Copilot reviewed 12 out of 14 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (2)

src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpProxyDiscoveryManager.cs:123

  • Cleanup uses the shared cancellation token. If cancellation is requested during discovery, ExitAsync can throw OperationCanceledException and skip the protocol shutdown, potentially leaving the MTP process running and leaking resources. Use a non-cancelable token for cleanup/shutdown.
        client.ExitAsync(_cancellationTokenSource.Token).GetAwaiter().GetResult();

src/Microsoft.TestPlatform.CrossPlatEngine/Client/MTP/MtpProxyExecutionManager.cs:391

  • ExitAsync is invoked with the shared cancellation token. If a run is canceled, this can prevent the shutdown request from being sent/awaited and may leave the MTP process alive. Use a non-cancelable token (and optionally swallow failures) for shutdown/cleanup paths.
        CollectAttachments(runResult, attachments);
        client.ExitAsync(_cancellationTokenSource.Token).GetAwaiter().GetResult();
        return client.ProcessId;

azat-msft and others added 3 commits July 28, 2026 17:02
The retarget onto Microsoft.Testing.Platform.ServerClient.Source left the MTP
glue with no unit coverage at all - the only tests were the end-to-end
MtpUnderVstestTests. The conversion code is now pure and dependency-free, so
cover it directly.

Add MtpTestNodeConverterTests and MtpClientOptionsFactoryTests (55 tests)
covering the normalized-Node contract, per-formatter number boxing, outcome
mapping, the action-node filter, vstest bridge properties, standard
output/error, traits, duration and log-level mapping.

Three fixes fall out of writing them:

- TryGetRawInt wrapped out-of-range values with unchecked((int)l), turning a
  bad line number into a plausible-looking wrong answer. Range-check instead so
  the property stays at its visibly-unset default.
- AddTraits collapsed every non-string trait value to an empty string. The two
  formatters box JSON scalars differently, so a numeric or boolean trait was
  silently dropped on one formatter and kept on the other. Format invariantly.
- MtpClientOptionsFactory re-read VSTEST_CONNECTION_TIMEOUT and hardcoded the
  90-second default instead of calling EnvironmentHelper.GetConnectionTimeout,
  which seven other vstest call sites already use and which also traces the
  override.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: cd0793f4-d530-44b6-b881-fed3be6aa52f
Retargeting onto the source package changed exit from a fire-and-forget
notification into an awaited request/response call, which introduced two
regressions:

- Exit was awaited on the run's own cancellation token. Cancelling or aborting
  a run is exactly when that token is already cancelled, so ExitAsync threw
  immediately and the graceful shutdown handshake was skipped in the one case
  it matters most.
- The await was unbounded, so a test application that never acknowledges exit
  would hang discovery or execution indefinitely. The notification it replaced
  could not block at all.

Route both proxy managers through MtpServerClientFactory: TryExit runs on its
own bounded token, swallows failures (the caller disposes the client next,
which tears the process down regardless), and is called from a finally block so
a failed or cancelled run still shuts the application down.

The factory also exposes a replaceable Launch delegate so the managers can be
driven against a fake server in unit tests; production always uses
MtpServerClient.Launch.

Separately, BuildUids substituted FullyQualifiedName when a TestCase carried no
MTP.TestNode.Uid. The server projects node.Uid alone when building a run filter
and never reads any other field, so that substitution produced a filter
matching nothing: the run reported success having executed zero of the tests
the user selected, with no error anywhere. Throw instead, with a comment
explaining why no fallback is correct.

Adds 15 tests covering the shutdown paths, the uid filter, and both manager
flows against a fake MTP server.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: cd0793f4-d530-44b6-b881-fed3be6aa52f
MTP frames declare Content-Length in UTF-8 bytes, but the transport shipped by
Microsoft.Testing.Platform.ServerClient.Source reads that number of characters:
it rents a char buffer of Content-Length and calls StreamReader.ReadBlockAsync.
For any frame carrying multi-byte UTF-8 the two disagree, so the reader
under-reads and leaves the body's tail to be parsed as the next frame's headers
- the connection desynchronizes from the following message onward.

vstest's deleted MtpServerConnection was byte-correct here (it read Content-Length
bytes into a byte[] and then UTF-8-decoded), so the retarget is a regression, not
an inherited defect. Client-to-server traffic is ASCII in practice, which is why
it has not surfaced; node updates flow the other way and carry user-authored test
names.

Give MtpMSTestProject a test whose display name mixes German umlauts (2 bytes
each), Japanese (3 bytes each) and an emoji (4 bytes, 2 chars), and mirror it in
MtpPureProject. Because the corruption lands on the message *after* the offending
one, its mere presence makes the whole run fail rather than just that test, so
every existing MTP scenario now exercises the transport with multi-byte content.
Adds a dedicated test asserting the name survives into the TRX.

These fail until the fix lands upstream in testfx.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: cd0793f4-d530-44b6-b881-fed3be6aa52f
azat-msft and others added 2 commits July 28, 2026 23:10
…ount

Running the acceptance test revealed two things worth recording.

First, an end-to-end MTP run cannot reproduce the Content-Length byte-vs-char
framing bug: the .NET MTP server serializes with System.Text.Json, whose default
encoder escapes every non-ASCII character to \\uXXXX, so the bytes on the wire
are ASCII and the byte count coincidentally equals the character count. The
framing bug is real but has to be proved at the unit level against the transport
directly, which is what the companion testfx change does. This test is therefore
a name-integrity guard, and its comments now say so rather than overclaiming.

Second, the emoji originally in the name exposed a separate defect: astral-plane
characters are escaped by System.Text.Json as a surrogate pair and arrive in the
TRX as the literal text \\ud83c\\udf89 instead of the character. BMP characters
decode correctly. That is its own bug, tracked separately, so the name is
narrowed to BMP multi-byte characters (umlauts 2 bytes, Japanese 3 bytes) which
still exercise the byte-denominated length without tripping over it.

Also updates the out-of-proc data collector's expected per-test-case attachment
count, which follows the test count.

MtpUnderVstestTests: 16/16 on both console axes.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: cd0793f4-d530-44b6-b881-fed3be6aa52f
Replaces the interim local-feed pack with a build of microsoft/testfx#10297,
which stacks the Content-Length byte/char fix onto microsoft#10085. The transport now
reads exactly Content-Length bytes and UTF-8-decodes them, symmetric with the
write path, and reads the headers through the same byte-level buffer so no
StreamReader can buffer part of the body across the boundary.

That drop also carries microsoft#10085's ServerRequestHandler signature change (the
result is now constrained to a serializable dictionary), so FakeMtpServerClient
is updated to match.

Verification on this drop:
- CrossPlatEngine builds clean on net462, netstandard2.0 and net8.0.
- MTP unit tests 140/140 (70 per axis, net11.0 and net481).
- MtpUnderVstestTests 16/16 on both console axes.

Note the 16/16: the two /logger:trx failures reported against the earlier drop
do not reproduce here, so they look like a local deployment issue rather than
anything in the retarget.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: cd0793f4-d530-44b6-b881-fed3be6aa52f
azat-msft and others added 4 commits July 28, 2026 23:23
Swaps the interim feed pack from the plain 2.4.0-dev build output to the
coordinator's canonical 2.4.0-dev.utf8fix1 drop of microsoft/testfx#10297.

Byte-equivalent content: all 184 contentFiles are identical between the two
packs, including TcpMessageHandler.cs with both ReadExactlyAsync and the
TrimPreamble BOM tolerance. Only the version metadata differs.

The rename is the point. While the package is served from a committed local
folder, NuGet caches by version, so a plain 2.4.0-dev risks silently resolving a
stale cache entry from an earlier drop of the same name. The unique suffix makes
that impossible, matching the convention the branch already used for
2.4.0-dev.numberfix.

Re-verified from a cleared package cache: CrossPlatEngine clean on all three
TFMs, MTP unit tests 140/140, MtpUnderVstestTests 16/16.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: cd0793f4-d530-44b6-b881-fed3be6aa52f
Localize the missing-uid error. The message reaches the user verbatim -
StartTestRun funnels ex.Message into HandleLogMessage(Error) - and every other
user-facing TestPlatformException in this assembly is resourced, so a hardcoded
English string formatted with CurrentCulture was self-contradictory. Adds
MtpTestCaseMissingNodeUid to Resources.resx, the generated designer property,
and a trans-unit to all 13 xlf files. The text now also states the remedy
(re-run discovery, or run without a selection) rather than only naming the
failure, and the comment records that aborting the whole source is deliberate:
silently running the addressable subset would recreate the same class of bug in
a smaller form.

Mark the three new test classes DoNotParallelize. MSTest parallelizes across
classes at MethodLevel by default here, and these classes mutate process-global
state - the MtpServerClientFactory.Launch seam and VSTEST_CONNECTION_TIMEOUT -
so a save/restore in TestInitialize/TestCleanup could restore one class's value
while another class's test was still relying on its own. That would have flaked
in CI looking like a product bug.

Close a hole in the float range guard. (float)int.MaxValue rounds *up* to
2147483648f, so comparing a float directly against int.MaxValue let that value
through and the cast then saturated - precisely the plausible-looking wrong
answer the guard exists to reject. Widen to double before comparing, and extend
the regression test to cover it.

Capture ProcessId before the exit handshake instead of reading it afterwards,
when the process may already be gone.

Test fixes: TryExitDoesNotUseAnAlreadyCancelledRunToken was vacuous (it built a
cancelled token it never passed anywhere) and LaunchDefaultsToTheRealClientLauncher
asserted only non-null, which any delegate satisfies. Both now assert something
that fails if the behaviour regresses. Adds the missing mixed-selection case,
where only some tests carry a uid.

Also fixes a stale test-count comment and softens an overclaim in
MtpPureProject, which no test currently references.

Unit tests 142/142 across net11.0 and net481; MtpUnderVstestTests 16/16 on both
console axes.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: cd0793f4-d530-44b6-b881-fed3be6aa52f
Picks up the two commits that landed on the testfx branch after the utf8fix1
pack: the header line buffer is now reused across lines instead of allocated per
line (server mode emits a notification per test, so that was a real hot-path
allocation), plus comments recording why Content-Length is intentionally not
capped and why the framing tests are not cross-TFM coverage.

Both changes are to TcpMessageHandler, which compiles into CrossPlatEngine, so
they are verified here rather than assumed. Re-verified from a cleared NuGet
package cache:

- CrossPlatEngine builds clean on net462, netstandard2.0 and net8.0.
- MTP unit tests 142/142 across net11.0 and net481.
- MtpUnderVstestTests 16/16 on both console axes.
- testfx's own ServerClient unit tests 48/48, confirming the shared transport is
  still good on both formatter paths.

The buffer is safe to hold as instance state for the same reason the existing
read offsets are: reads are single-threaded, driven by exactly one read loop.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: cd0793f4-d530-44b6-b881-fed3be6aa52f
Harden the MTP client: UTF-8 framing, shutdown, uid filter, and tests
Copilot AI review requested due to automatic review settings July 30, 2026 13:52

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Pull request overview

Copilot reviewed 36 out of 39 changed files in this pull request and generated no new comments.

Files not reviewed (1)
  • src/Microsoft.TestPlatform.CrossPlatEngine/Resources/Resources.Designer.cs: Generated file
Comments suppressed due to low confidence (1)

test/TestAssets/MtpPureProject/PureTestFramework.cs:20

  • The summary says this asset “mirrors the MSTest asset”, but MtpMSTestProject currently has 6 test methods (it also includes RunSettingsEnvironmentVariableIsInjected). This comment is now misleading; consider rewording to avoid claiming exact parity while keeping the expected counts for this asset correct.

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3 participants