add test stack for stack type (#1211)

Co-authored-by: Martin Robertz <dream-master@gmx.net>

src/main/java/appeng/api/storage/data/IAEStackType.java

@@ -103,4 +103,6 @@ public interface IAEStackType<T extends IAEStack> {
      */
     @SideOnly(Side.CLIENT)
     IIcon getButtonIcon();
+
+    T getTestStack();
 }

src/main/java/appeng/util/item/AEFluidStackType.java

@@ -1,7 +1,9 @@
 package appeng.util.item;
 
 import java.io.IOException;
+import java.util.Objects;
 
+import net.minecraft.init.Items;
 import net.minecraft.item.ItemStack;
 import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.util.EnumChatFormatting;
@@ -201,4 +203,14 @@ public class AEFluidStackType implements IAEStackType<IAEFluidStack> {
             }
         };
     }
+
+    @NotNull
+    private final IAEFluidStack testStack = Objects
+            .requireNonNull(this.getStackFromContainerItem(new ItemStack(Items.water_bucket, 1)));
+
+    @Override
+    @NotNull
+    public IAEFluidStack getTestStack() {
+        return this.testStack.copy();
+    }
 }

src/main/java/appeng/util/item/AEItemStackType.java

@@ -2,6 +2,7 @@ package appeng.util.item;
 
 import java.io.IOException;
 
+import net.minecraft.init.Blocks;
 import net.minecraft.item.ItemStack;
 import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.util.EnumChatFormatting;
@@ -168,4 +169,13 @@ public class AEItemStackType implements IAEStackType<IAEItemStack> {
             }
         };
     }
+
+    @NotNull
+    private final IAEItemStack testStack = AEItemStack.create(new ItemStack(Blocks.fire));
+
+    @Override
+    @NotNull
+    public IAEItemStack getTestStack() {
+        return this.testStack.copy();
+    }
 }