Testing: Add test suite to project

Adding a simple test suite for configuring and building each project.
Also adding info to the readme on how to run the tests.

Author: etcwilde

CMakeLists.txt

@@ -0,0 +1,43 @@
+# This source file is part of the Swift open source project
+#
+# Copyright (c) 2025 Apple Inc. and the Swift project authors.
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See https://swift.org/LICENSE.txt for license information
+# =============================================================================
+# This file configure testing that each project configures and builds with
+# ctest.
+# It is not meant for configuring and building each project.
+
+cmake_minimum_required(VERSION 3.22)
+project(SwiftCMakeExamples LANGUAGES NONE)
+
+include(CTest)
+
+function(add_cmake_test name source_dir)
+  cmake_parse_arguments(PARSE_ARGV 2 ARG "" "CMAKE_VERSION" "" )
+  if(NOT ARG_CMAKE_VERSION)
+    set(ARG_CMAKE_VERSION 3.22)
+  endif()
+
+  if(${CMAKE_VERSION} VERSION_LESS ${ARG_CMAKE_VERSION})
+    message(STATUS "Skipping ${name} -- CMake version too old: ${CMAKE_VERSION} < ${ARG_CMAKE_VERSION}")
+    return()
+  endif()
+
+  add_test(NAME "${name}-configure"
+    COMMAND ${CMAKE_COMMAND}
+      -G ${CMAKE_GENERATOR}
+      -B "${name}-build"
+      -S "${CMAKE_CURRENT_SOURCE_DIR}/${source_dir}"
+      -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE})
+  add_test(NAME "${name}-build" COMMAND
+    ${CMAKE_COMMAND} --build "${name}-build")
+  set_tests_properties("${name}-build" PROPERTIES DEPENDS "${name}-configure")
+endfunction()
+
+add_cmake_test(SingleExecutable 1_single_executable)
+add_cmake_test(ExecutableLibrary 2_executable_library)
+add_cmake_test(BidirectionalCxxInterop 3_bidirectional_cxx_interop
+  CMAKE_VERSION 3.26)
+add_cmake_test(SwiftMacros 4_swift_macros)

README.md

@@ -57,3 +57,22 @@ using the Swift macro support introduced in Swift 5.9.
 Requires:
 
  - Swift 5.9 (macOS: Swift 5.9.0, Windows and Linux: Swift 5.9.1)
+
+# Testing
+
+Tests are run with `ctest`, configured with the CMakeLists at the top-level.
+
+```sh
+cmake -G Ninja -B build -S .
+cd build
+ctest -j --output-on-failure
+```
+
+When you add a test, add it to the top-level CMakeLists file and re-run CMake
+from the test directory to ensure that the CTest files are updated
+appropriately before trying to run the tests.
+
+```sh
+cmake .
+ctest -j --output-on-failure
+```