Block texture is loaded successfully, but the 'BlockItem' texture isn't, Minecraft Forge 1.15.2

I've tried many tutorials and looked for documentation, but yet haven't succeeded. I'll show you my code files directory and an image of the problem.

testmod/TestMod.java :

package com.SkySibe.testmod;


import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.event.lifecycle.FMLClientSetupEvent;
import net.minecraftforge.fml.event.lifecycle.FMLCommonSetupEvent;
import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

// The value here should match an entry in the META-INF/mods.toml file
@Mod("testmod")
public class TestMod
{
    // Directly reference a log4j logger.
    private static final Logger LOGGER = LogManager.getLogger();
    public static final String MOD_ID = "testmod";
    public static TestMod instance;

    public TestMod() {
        // Register the setup method for modloading
        FMLJavaModLoadingContext.get().getModEventBus().addListener(this::setup);
        // Register the doClientStuff method for modloading
        FMLJavaModLoadingContext.get().getModEventBus().addListener(this::doClientStuff);

        instance = this;

        // Register ourselves for server and other game events we are interested in
        MinecraftForge.EVENT_BUS.register(this);
    }

    private void setup(final FMLCommonSetupEvent event)
    {

    }

    private void doClientStuff(final FMLClientSetupEvent event) {

    }

}

testmod/init/BlockInit.java :

package com.SkySibe.testmod.init;

import com.SkySibe.testmod.TestMod;

import net.minecraft.block.Block;
import net.minecraft.block.OreBlock;
import net.minecraft.block.SoundType;
import net.minecraft.block.material.Material;
import net.minecraft.item.BlockItem;
import net.minecraft.item.Item;
import net.minecraft.item.ItemGroup;
import net.minecraftforge.common.ToolType;
import net.minecraftforge.event.RegistryEvent;
import net.minecraftforge.eventbus.api.SubscribeEvent;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.common.Mod.EventBusSubscriber.Bus;
import net.minecraftforge.registries.ObjectHolder;

@ObjectHolder(TestMod.MOD_ID)
@Mod.EventBusSubscriber(modid = TestMod.MOD_ID, bus = Bus.MOD)
public class BlockInit {
    public static final Block ruby_ore = null;

    @SubscribeEvent
    public static void registerBlocks(final RegistryEvent.Register<Block> event) {
        event.getRegistry().register(new OreBlock(Block.Properties.create(Material.ROCK).hardnessAndResistance(3.0F, 3.0F).sound(SoundType.STONE).harvestTool(ToolType.PICKAXE)).setRegistryName("ruby_ore"));
    }

    @SubscribeEvent
    public static void registerBlockItems(final RegistryEvent.Register<Item> event) {
        event.getRegistry().register(new BlockItem(ruby_ore,new Item.Properties().group(ItemGroup.BUILDING_BLOCKS)).setRegistryName("ruby_ore"));
    }
}

assets/testmod/blockstates/ruby_ore.json :

{
    "variants": {
        "": { "model": "testmod:block/ruby_ore"}
    }
}

assets/testmod/models/block/ruby_ore.json :

{
    "parent": "block/cube_all",
    "textures": {
        "all": "testmod:blocks/ruby_ore"
    }
}

assets/testmod/models/item/ruby_ore.json :

{
    "parent": "testmod:block/ruby_block"
}