This is a tutorial on how to have Minecraft textures on Minetest. I would put a link but that would violate copyright, so follow the instructions. This is written for Linux; it should work very similarly on Mac but you might have to tinker some on Windows.
1 - You'll want to have a folder to keep everything in. Make that now.
2 - Go to https://mcversions.net/, and download the client JAR of the latest release. Put that in your folder.
3 - Extract ONLY THE "assets" FOLDER. Do not extract anything else.
4 - Download ZNixian's Minecraft to Minetest Texture Converter at https://github.com/ZNixian/minecraft-to-minetest-tp-conv/archive/master.zip.
5 - Extract the "mc-to-mt-tp-conv" folder and put it in the extracted "assets" folder.
6 - Open Terminal, go to "mc-to-mt-tp-conv", and run "./conv.sh".
7 - You now have your texture pack, located at "[your folder]/assets/minetest-texture-pack".
8 - Rename the texture pack folder to "minecraft".
9 - Place the folder in your Minetest texture pack directory, for me it was "~/.minetest/textures".
There you go, enjoy :D