api-test-ws-h2-txcredit: ws-over-h2 tx flow-control selftest

A ws server vhost and an RFC 8441 h2 ws client in one process.  The
server bulk-sends a 64KB pattern in 1KB lws_write() chunks gated only
on lws_send_pipe_choked(), like typical user code; the client connects
with LCCSCF_H2_MANUAL_RXFLOW and drip-feeds tx credit in 1KB
WINDOW_UPDATE quanta, forcing the h2 role to park DATA and split
frames to fit the window.

Fails (within a second) if the connection doesn't come up as genuine
ws-over-h2, if the client ever receives more ws payload than it has
granted credit for -- only possible when the server ignored the peer's
window -- or if the pattern is corrupted / incomplete; passes when the
whole transfer arrives in-window.  Wired into ctest like the other
api-tests.

Author: thefallentree

minimal-examples-lowlevel/api-tests/api-test-ws-h2-txcredit/CMakeLists.txt

@@ -0,0 +1,36 @@
+project(lws-api-test-ws-h2-txcredit C)
+cmake_minimum_required(VERSION 3.10)
+find_package(libwebsockets CONFIG REQUIRED)
+list(APPEND CMAKE_MODULE_PATH ${LWS_CMAKE_DIR})
+include(CheckCSourceCompiles)
+include(LwsCheckRequirements)
+
+set(SAMP lws-api-test-ws-h2-txcredit)
+set(SRCS main.c)
+
+set(requirements 1)
+require_lws_config(LWS_ROLE_WS 1 requirements)
+require_lws_config(LWS_ROLE_H2 1 requirements)
+require_lws_config(LWS_WITH_CLIENT 1 requirements)
+require_lws_config(LWS_WITH_SERVER 1 requirements)
+require_lws_config(LWS_WITH_TLS 1 requirements)
+
+if (requirements)
+	add_executable(${SAMP} ${SRCS})
+
+	if (websockets_shared)
+		target_link_libraries(${SAMP} websockets_shared ${LIBWEBSOCKETS_DEP_LIBS})
+		add_dependencies(${SAMP} websockets_shared)
+	else()
+		target_link_libraries(${SAMP} websockets ${LIBWEBSOCKETS_DEP_LIBS})
+	endif()
+
+	lws_get_free_port(PORT_WS_H2_TXCR)
+
+	add_test(NAME api-test-ws-h2-txcredit COMMAND lws-api-test-ws-h2-txcredit -p ${PORT_WS_H2_TXCR})
+	set_tests_properties(api-test-ws-h2-txcredit
+			     PROPERTIES
+			     WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}/minimal-examples-lowlevel/api-tests/api-test-ws-h2-txcredit
+			     TIMEOUT 60)
+
+endif()