json: Error in test\download_test_data.vcxproj custom build step when compiling with Visual Studio 2019 16.7.7 msbuild on Windows 10

I get the following error in the CustomBuild step of test\download_test_data.vcxproj when compiling with Visual Studio 2019 16.7.7 Professional msbuild on Windows 10 2004 Professional:

CustomBuild: Downloading test data from https://github.com/nlohmann/json_test_data (v3.0.0) Der Befehl “test” ist entweder falsch geschrieben oder konnte nicht gefunden werden. Building Custom Rule ./test/CMakeLists.txt

The Command “test” is not found, because it does not exist on Windows. “test -d json_test_data” is found in the CustomBuild step of the test\download_test_data.vcxproj project.

The problem is located in download_test_data.cmake “COMMAND test -d json_test_data || …”, here “COMMAND if not exist json_test_data …” should be used on Windows.

Please describe the steps to reproduce the issue.

1. Download json-3.9.1.zip and unzip
2. Open a Developer command Prompt v16.7.7
3. cd json-3.9.1
4. Create directory build and cd build
5. cmake …\ -D JSON_Install:BOOL=OFF -D JSON_ImplicitConversions:BOOL=OFF -D JSON_BuildTests:BOOL=ON
6. msbuild nlohmann_json.sln
7. msbuild nlohmann_json.sln

What is the expected behavior?

No error.

And what is the actual behavior instead?

Step 6: CustomBuild: Downloading test data from https://github.com/nlohmann/json_test_data (v3.0.0) Der Befehl “test” ist entweder falsch geschrieben oder konnte nicht gefunden werden. Building Custom Rule ./test/CMakeLists.txt

Step 7: CustomBuild: Downloading test data from https://github.com/nlohmann/json_test_data (v3.0.0) Der Befehl “test” ist entweder falsch geschrieben oder konnte nicht gefunden werden. fatal: destination path ‘json_test_data’ already exists and is not an empty directory. c:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\MSBuild\Microsoft\VC\v160\Microsoft.CppCommon.targets(234,5): error MSB6006: “cmd.exe” wurde mit dem Code 128 beendet. [build\test\download_test_data.vcxproj]

Which compiler and operating system are you using?

• Compiler: Visual Studio 2019 16.7.7 Professional
• Operating system: Windows 10 2004 Pro German

Which version of the library did you use?

• [x ] latest release version 3.9.1

If you experience a compilation error: can you compile and run the unit tests?

• yes
• no - please copy/paste the error message below

ctest --output-on-failure

did not work, there is mising a -C <config> in the command

ctest -C Release --output-on-failure

would do the job, but an error is reported about json_test_data. After deleting the json_test_data folder and executing

ctest -C Release --output-on-failure

it works. Is also works without deleting the folder when “if exist” is used instead of “test” as reported on top of this post.

Total Test time (real) = 381.65 sec

The following tests FAILED: 51 - cmake_import_configure (Failed) 52 - cmake_import_build (Not Run) 53 - cmake_import_minver_configure (Failed) 54 - cmake_import_minver_build (Not Run) 57 - cmake_fetch_content_configure (Failed) 58 - cmake_fetch_content_build (Not Run) Errors while running CTest