Tests: Add cases covering our mkdtemp code paths

* `cmSystemTools::MakeTempDirectory` is our own code.

* `uv_fs_mkdtemp` requires patching to backport to platforms
  not supported by upstream libuv.

Tests/CMakeLib/CMakeLists.txt

@@ -33,6 +33,7 @@ set(CMakeLib_TESTS
   testFindPackageCommand.cxx
   testUVHandlePtr.cxx
   testUVJobServerClient.cxx
+  testUVPatches.cxx
   testUVProcessChain.cxx
   testUVRAII.cxx
   testUVStreambuf.cxx

Tests/CMakeLib/testSystemTools.cxx

@@ -96,11 +96,34 @@ static bool testStrVersCmp()
   return true;
 }
 
+static bool testMakeTempDirectory()
+{
+  std::cout << "testMakeTempDirectory()\n";
+
+  static std::string const kTemplate = "testMakeTempDirectory-XXXXXX";
+  std::string tempDir = kTemplate;
+  cmsys::Status status = cmSystemTools::MakeTempDirectory(tempDir);
+  if (!status) {
+    std::cout << "cmSystemTools::MakeTempDirectory failed on \"" << tempDir
+              << "\": " << status.GetString() << '\n';
+    return false;
+  }
+  if (!cmSystemTools::FileIsDirectory(tempDir)) {
+    std::cout << "cmSystemTools::MakeTempDirectory did not create \""
+              << tempDir << '\n';
+    return false;
+  }
+  cmSystemTools::RemoveADirectory(tempDir);
+  ASSERT_TRUE(tempDir != kTemplate);
+  return true;
+}
+
 int testSystemTools(int /*unused*/, char* /*unused*/[])
 {
   return runTests({
     testUpperCase,
     testVersionCompare,
     testStrVersCmp,
+    testMakeTempDirectory,
   });
 }

Tests/CMakeLib/testUVPatches.cxx

@@ -0,0 +1,46 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+
+#include <cmConfigure.h> // IWYU pragma: keep
+
+#include <string>
+
+#include <cm3p/uv.h>
+
+#include "cmSystemTools.h"
+
+#include "testCommon.h"
+
+static bool test_uv_fs_mkdtemp()
+{
+  std::cout << "test_uv_fs_mkdtemp()\n";
+  static std::string const kTemplate = "test-uv_fs_mkdtemp-XXXXXX";
+  std::string tempDir;
+  uv_fs_t tempDirReq;
+  tempDirReq.data = &tempDir;
+  uv_loop_t* loop = uv_default_loop();
+  int r =
+    uv_fs_mkdtemp(loop, &tempDirReq, kTemplate.c_str(), [](uv_fs_t* req) {
+      if (req->data && req->path) {
+        *static_cast<std::string*>(req->data) = req->path;
+      }
+    });
+  ASSERT_EQUAL(r, 0);
+  uv_run(loop, UV_RUN_DEFAULT);
+  uv_fs_req_cleanup(&tempDirReq);
+  if (!cmSystemTools::FileIsDirectory(tempDir)) {
+    std::cout << "cmSystemTools::MakeTempDirectory did not create \""
+              << tempDir << '\n';
+    return false;
+  }
+  cmSystemTools::RemoveADirectory(tempDir);
+  ASSERT_TRUE(tempDir != kTemplate);
+  return true;
+}
+
+int testUVPatches(int /*unused*/, char* /*unused*/[])
+{
+  return runTests({
+    test_uv_fs_mkdtemp,
+  });
+}