cmake: Add DiscoverTests module

diff --git a/cmake/DiscoverTests.cmake b/cmake/DiscoverTests.cmake
new file mode 100644
index 0000000..683780a
--- /dev/null
+++ b/cmake/DiscoverTests.cmake
@@ -0,0 +1,71 @@
+# TODO: rework/remove once test discovery is implemented upstream:
+# https://gitlab.kitware.com/cmake/cmake/-/issues/26920
+function(discover_tests target)
+  set(options "")
+  set(oneValueArgs DISCOVERY_MATCH TEST_NAME_REPLACEMENT TEST_ARGS_REPLACEMENT)
+  set(multiValueArgs DISCOVERY_ARGS PROPERTIES)
+  cmake_parse_arguments(PARSE_ARGV 1 arg "${options}" "${oneValueArgs}" "${multiValueArgs}")
+
+  set(file_base ${CMAKE_CURRENT_BINARY_DIR}/${target})
+  set(include_file ${file_base}_include.cmake)
+
+  set(properties_content)
+  list(LENGTH arg_PROPERTIES properties_len)
+  if(properties_len GREATER "0")
+    set(properties_content "      set_tests_properties(\"\${test_name}\" PROPERTIES\n")
+    math(EXPR num_properties "${properties_len} / 2")
+    foreach(i RANGE 0 ${num_properties} 2)
+      math(EXPR value_index "${i} + 1")
+      list(GET arg_PROPERTIES ${i} name)
+      list(GET arg_PROPERTIES ${value_index} value)
+      string(APPEND properties_content "        \"${name}\" \"${value}\"\n")
+    endforeach()
+    string(APPEND properties_content "      )\n")
+  endif()
+
+  string(CONCAT include_content
+    "set(runner   [[$<TARGET_FILE:${target}>]])\n"
+    "set(launcher [[$<TARGET_PROPERTY:${target},TEST_LAUNCHER>]])\n"
+    "set(emulator [[$<$<BOOL:${CMAKE_CROSSCOMPILING}>:$<TARGET_PROPERTY:${target},CROSSCOMPILING_EMULATOR>>]])\n"
+    "\n"
+    "execute_process(\n"
+    "  COMMAND \${launcher} \${emulator} \${runner} ${arg_DISCOVERY_ARGS}\n"
+    "  OUTPUT_VARIABLE output OUTPUT_STRIP_TRAILING_WHITESPACE\n"
+    "  ERROR_VARIABLE  output ERROR_STRIP_TRAILING_WHITESPACE\n"
+    "  RESULT_VARIABLE result\n"
+    ")\n"
+    "\n"
+    "if(NOT result EQUAL 0)\n"
+    "  add_test([[${target}_DISCOVERY_FAILURE]] \${launcher} \${emulator} \${runner} ${arg_DISCOVERY_ARGS})\n"
+    "else()\n"
+    "  string(REPLACE \"\\n\" \";\" lines \"\${output}\")\n"
+    "  foreach(line IN LISTS lines)\n"
+    "    if(line MATCHES \"${arg_DISCOVERY_MATCH}\")\n"
+    "      string(REGEX REPLACE \"${arg_DISCOVERY_MATCH}\" \"${arg_TEST_NAME_REPLACEMENT}\" test_name \"\${line}\")\n"
+    "      string(REGEX REPLACE \"${arg_DISCOVERY_MATCH}\" \"${arg_TEST_ARGS_REPLACEMENT}\" test_args \"\${line}\")\n"
+    "      separate_arguments(test_args)\n"
+    "      add_test(\"\${test_name}\" \${launcher} \${emulator} \${runner} \${test_args})\n"
+    ${properties_content}
+    "    endif()\n"
+    "  endforeach()\n"
+    "endif()\n"
+  )
+
+  get_property(is_multi_config GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
+  if(is_multi_config)
+    file(GENERATE
+      OUTPUT ${file_base}_include-$<CONFIG>.cmake
+      CONTENT "${include_content}"
+    )
+    file(WRITE ${include_file}
+      "include(\"${file_base}_include-\${CTEST_CONFIGURATION_TYPE}.cmake\")"
+    )
+  else()
+    file(GENERATE
+      OUTPUT ${include_file}
+      CONTENT "${include_content}"
+    )
+  endif()
+
+  set_property(DIRECTORY APPEND PROPERTY TEST_INCLUDE_FILES ${include_file})
+endfunction()