What

Summary

Adds hermetic branch coverage tests for src/protocols/grpc/client.cpp, exercising public-API surfaces that remained uncovered after the initial coverage work in #994. The new test file tests/unit/grpc_client_branch_test.cpp adds 51 test cases across 12 test suites, complementing the existing grpc_client_test.cpp and core_client_test.cpp.

Change Type

• Test

Why

Related Issues

• Closes test: expand coverage for src/protocols/grpc/client.cpp #1049
• Part of Expand unit test coverage from 40% to 80% #953

Motivation

src/protocols/grpc/client.cpp was measured at line 22.6% / branch 9.5% on develop @ 05c1b7bb (2026-04-26 baseline) and concentrates uncovered code in error and boundary paths — exactly the surfaces that regress during the ongoing Result<T> migration. Raising coverage of this file contributes directly to the #953 acceptance criteria (line >= 70% / branch >= 60% per file). This PR adds hermetic tests that exercise public-facing surfaces (config round-trip, call_options, lifecycle, guard clauses, async callbacks, metadata semantics) without requiring a live gRPC peer.

Where

Files Changed

• tests/unit/grpc_client_branch_test.cpp (new, 542 lines, 51 test cases)
• tests/CMakeLists.txt (registration of network_grpc_client_branch_test)
• CHANGELOG.md (one-line entry under [Unreleased] > Added)
• docs/CHANGELOG.md (multi-line detailed entry under [Unreleased] > Added)

How

Implementation Highlights

Test groups in grpc_client_branch_test.cpp:

• GrpcClientChannelConfigBoundary — full-field round-trip with all-zero / all-max / default / partial mutual-TLS configurations
• GrpcClientCallOptionsSetTimeout — set_timeout across chrono::seconds / milliseconds / microseconds / nanoseconds, zero-timeout, deadline overwrite, monotonicity
• GrpcClientCallOptionsMetadata — empty key / empty value / 64 ordered entries / 8 KiB value / binary-flagged key / clear-resets-empty
• GrpcClientConstructionTargets — long, IPv6 bracket, DNS, with-path, port-65535, identical-target permutations
• GrpcClientWaitForConnectedBudget — 0 / 1 / 50 ms timeouts, repeated-call idempotency
• GrpcClientDisconnectIdempotency — 32 sequential disconnects, 4-thread concurrent disconnects, 8-thread is_connected polling (1600 observations), concurrent disconnect-while-querying
• GrpcClientMoveSemantics — move construct / move assign / 4-step move chain / disconnect-after-move
• GrpcClientConnectMalformed — leading / trailing / only colon, multi-colon, space-in-port, negative-leading port, > 63-char DNS label (default-transport build only)
• GrpcClientCallRawGuards — empty method, no-leading-slash, 64 KiB payload, pre-expired deadline, future deadline, wait_for_ready=true, compression algorithm set, post-disconnect
• GrpcClientStreamingGuards — server / client / bidi streaming with empty methods, missing-slash methods, expired deadline, post-disconnect
• GrpcClientCallRawAsyncStress — 8-callback concurrent stress with deterministic notification, null-callback safety with non-empty payload and with deadline
• GrpcMetadataSemantics — copy / move / assignment-from-empty / erase

Honest scope statement

This PR covers the surfaces that are reachable via the public API without a live gRPC peer. The impl-level methods that physically exchange frames with a peer remain at zero hits and would require a transport fixture (or in-process loopback test peer) to drive:

• grpc_client::impl::call_raw body after the is_connected()==true branch (HTTP/2 post() round-trip in default transport, stub_->UnaryCall in official-grpcpp build)
• server_stream_reader_impl::on_data / on_headers / on_complete — invoked by HTTP/2 stream callbacks
• client_stream_writer_impl::write / writes_done / finish round-trip — requires server response
• bidi_stream_impl::read / write / writes_done / finish — requires bidi peer
• grpc_client::impl::server_stream_raw / client_stream_raw / bidi_stream_raw body after the is_connected()==true and method-validation guards
• Tracing span->set_attribute / span->set_error calls on successful call paths (only reachable when tracing is enabled and a call completes)

The hermetic suite covers everything that returns synchronously without crossing the network boundary: config validation, option construction, lifecycle, guard clauses, async-callback delivery for the not-connected case, and value-type semantics. A separate sub-issue (or in-process gRPC test fixture work under #953) is required to push coverage of the frame-exchange paths above the line/branch thresholds.

Testing Done

• Tests added: 51 test cases in 12 test suites (~542 lines)
• Local build: skipped — cmake/ctest not installed in sandbox
• Will rely on CI (Coverage Analysis + ubuntu/macos x Debug/Release matrix)

Breaking Changes

None — test-only additions and CHANGELOG entries.