What

Summary

Adds tests/unit/http2_server_branch_test.cpp with 41 hermetic test cases across 9 suites, exercising public-API surfaces of src/protocols/http2/http2_server.cpp that remained uncovered after Issue #992. Complements the existing http2_server_test.cpp and http2_server_coverage_test.cpp by extending boundary-value, concurrency, and lifecycle coverage without requiring a live HTTP/2 client.

Change Type

• Test

Why

Related Issues

• Closes test: expand coverage for src/protocols/http2/http2_server.cpp #1050
• Part of Expand unit test coverage from 40% to 80% #953

Motivation

src/protocols/http2/http2_server.cpp had a 2026-04-26 baseline of line 38.3% / branch 19.4% on develop @ 05c1b7bb. The uncovered surfaces concentrate in boundary handling (zero / max settings values, empty / long server IDs), pre-listen state queries, repeated lifecycle cycles, and concurrent reader/writer interactions on the settings + state-query APIs. Raising hermetic coverage for these surfaces now contributes directly to the #953 ecosystem-wide 80% line / 70% branch goal and follows the same pattern as siblings #1048 (PR #1054) and #1049 (PR #1055).

Where

Files Changed

• tests/unit/http2_server_branch_test.cpp (new, ~568 lines)
• tests/CMakeLists.txt (registers network_http2_server_branch_test)
• CHANGELOG.md, docs/CHANGELOG.md ([Unreleased] > Added entry)

How

Implementation Highlights

The test file is organised into 9 TEST_F / TEST suites, each targeting a distinct surface:

• Http2ServerTlsConfigRoundTrip (4 tests) — tls_config field round-trips with empty / 1024-char / binary-byte paths, plus verify_client toggle that does not perturb other fields.
• Http2ServerConstructionIds (5 tests) — construction with empty / 512-char / binary-byte server IDs, multi-instance independence, 16-iteration repeated construction.
• Http2ServerSettingsRoundTrip (6 tests) — all-zero and all-UINT32_MAX http2_settings round-trips via set_settings / get_settings, default-value baseline, repeated header_table_size updates exercising HPACK encoder / decoder dynamic-table updates, enable_push toggle invariance, independent settings across instances.
• Http2ServerPreListenStateTest (6 tests) — pre-listen state queries (is_running, active_connections, active_streams, server_id) and stop() idempotency before any start().
• Http2ServerCycleTest (7 tests) — 4-iteration start / stop cycles on ephemeral port 0, start() already-running rejection, start_tls() already-running rejection (after a successful start()), zero counters after stop, destructor-while-running cleanup, wait() completion after stop() on a separate thread.
• Http2ServerTlsRejectTest (5 tests) — start_tls() rejection paths (default-empty config, both files missing, verify_client=true with missing CA, repeated rejection idempotency, post-failed-TLS clear-start recovery).
• Http2ServerHandlerCoverageTest (5 tests) — handler registration with default-constructed std::function, move-only-captured unique_ptr, and triple replacement of both request and error handlers.
• Http2ServerConcurrentQueries (5 tests) — 8-thread is_running polling, 4-thread active_connections / active_streams / server_id polling (200 iterations each), concurrent writer/reader pair on set_settings / get_settings.
• Http2ServerMultiInstance (2 tests) — 4 concurrent servers running on independent ephemeral ports plus stop-one-affects-none.

Honest scope statement

The impl-level frame-handler paths in http2_server_connection cannot be exercised hermetically and remain at 0 hits in this suite:

• process_frame per-frame_type switch cases (settings / headers / data / rst_stream / ping / goaway / window_update branches)
• handle_settings_frame + send_settings_ack (peer SETTINGS application + ACK emission)
• handle_headers_frame HPACK decode + COMPRESSION_ERROR GOAWAY emission
• handle_data_frame window-update emission and unknown-stream RST_STREAM emission
• handle_rst_stream_frame stream close
• handle_ping_frame ACK reply
• handle_goaway_frame shutdown reaction
• handle_window_update_frame flow-control accounting
• get_or_create_stream, close_stream
• send_frame, send_settings (frame serialisation + write)
• read_frame_header, read_frame_payload success branches
• dispatch_request (request-handler invocation + post-handler stream close)
• The TLS handshake error path inside handle_accept_tls

Driving these requires either a mock client that speaks the HTTP/2 wire format end-to-end (preface + SETTINGS exchange + per-frame round-trips) or a friend-declared injection point inside http2_server_connection. Neither is in scope for this hermetic test sub-issue. The existing http2_server_coverage_test.cpp partially exercises preface handling via raw TCP clients, but the per-frame branches require a real HTTP/2 client. This same structural blocker was acknowledged honestly in the sibling PRs #1054 (#1048) and #1055 (#1049).

Testing Done

• Tests added: 45 test cases in 9 test suites
• Local build: skipped — cmake/ctest not installed in sandbox
• Will rely on CI (Coverage Analysis + ubuntu/macos x Debug/Release matrix, plus ASAN/TSAN/UBSAN sanitizer jobs)

Breaking Changes

None — test-only additions.