Update Gradle.

gradle/wrapper/gradle-wrapper.properties

@@ -2,4 +2,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.9-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6-bin.zip

src/test/java/com/refinedmods/refinedstorage/apiimpl/util/ItemStackListTest.java

@@ -0,0 +1,195 @@
+package com.refinedmods.refinedstorage.apiimpl.util;
+
+import com.refinedmods.refinedstorage.api.util.StackListResult;
+import net.minecraft.item.ItemStack;
+import net.minecraft.item.Items;
+import net.minecraft.nbt.CompoundNBT;
+import org.junit.jupiter.api.Test;
+
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class ItemStackListTest extends MinecraftTest {
+    private final ItemStackList list = new ItemStackList();
+
+    @Test
+    void Test_adding_a_stack_without_any_existing_stack_present() {
+        // Arrange
+        ItemStack toAdd = new ItemStack(Items.DIRT);
+
+        // Act
+        StackListResult<ItemStack> result = list.add(toAdd, 10);
+
+        // Assert
+        assertThat(result.getChange()).isEqualTo(10);
+        assertThat(result.getId()).isNotNull();
+        assertThat(result.getStack().getItem()).isEqualTo(Items.DIRT);
+        assertThat(result.getStack().getCount()).isEqualTo(10);
+        assertThat(result.getStack().getTag()).isNull();
+        assertThat(result.getStack()).isNotSameAs(toAdd);
+
+        assertThat(list.size()).isEqualTo(1);
+    }
+
+    @Test
+    void Test_adding_a_stack_with_an_existing_stack_present_should_merge_if_same_stack() {
+        // Arrange
+        ItemStack toAdd1 = new ItemStack(Items.DIRT);
+        ItemStack toAdd2 = new ItemStack(Items.DIRT);
+
+        // Act
+        UUID id = list.add(toAdd1, 10).getId();
+        StackListResult<ItemStack> result = list.add(toAdd2, 10);
+
+        // Assert
+        assertThat(result.getStack()).isNotSameAs(toAdd1).isNotSameAs(toAdd2);
+        assertThat(result.getChange()).isEqualTo(10);
+        assertThat(result.getId()).isNotNull();
+        assertThat(result.getStack().getItem()).isEqualTo(Items.DIRT);
+        assertThat(result.getStack().getCount()).isEqualTo(20);
+        assertThat(result.getStack().getTag()).isNull();
+
+        assertThat(list.size()).isEqualTo(1);
+    }
+
+    @Test
+    void Test_adding_a_stack_with_an_existing_stack_present_should_not_merge_if_different_item() {
+        // Arrange
+        ItemStack toAdd1 = new ItemStack(Items.DIRT, 1);
+        ItemStack toAdd2 = new ItemStack(Items.GLASS);
+        ItemStack toAdd3 = new ItemStack(Items.DIRT, 5);
+
+        // Act
+        list.add(toAdd1, 10);
+        list.add(toAdd2, 10);
+        list.add(toAdd3, 10);
+
+        // Assert
+        assertThat(list.size()).isEqualTo(2);
+    }
+
+    @Test
+    void Test_adding_a_stack_with_an_existing_stack_present_should_not_merge_if_same_item_but_different_tag() {
+        // Arrange
+        ItemStack toAdd1 = new ItemStack(Items.DIRT);
+        ItemStack toAdd2 = new ItemStack(Items.GLASS);
+        ItemStack toAdd3 = new ItemStack(Items.DIRT);
+        CompoundNBT testTag = new CompoundNBT();
+        testTag.putInt("a", 1);
+        toAdd3.setTag(testTag);
+
+        // Act
+        list.add(toAdd1, 10);
+        list.add(toAdd2, 10);
+        list.add(toAdd3, 10);
+
+        // Assert
+        assertThat(list.size()).isEqualTo(3);
+    }
+
+    @Test
+    void Test_adding_invalid_stacks_should_fail() {
+        assertThrows(IllegalArgumentException.class, () -> list.add(ItemStack.EMPTY));
+        assertThrows(IllegalArgumentException.class, () -> list.add(new ItemStack(Items.DIRT), -1));
+        assertThrows(IllegalArgumentException.class, () -> list.add(new ItemStack(Items.DIRT), 0));
+    }
+
+    @Test
+    void Test_adding_too_big_stacks_should_not_overflow() {
+        ItemStack current = list.add(new ItemStack(Items.DIRT), Integer.MAX_VALUE - 5).getStack();
+        assertThat(current.getCount()).isEqualTo(Integer.MAX_VALUE - 5);
+
+        current = list.add(new ItemStack(Items.DIRT), 4).getStack();
+        assertThat(current.getCount()).isEqualTo(Integer.MAX_VALUE - 1);
+
+        current = list.add(new ItemStack(Items.DIRT), 1).getStack();
+        assertThat(current.getCount()).isEqualTo(Integer.MAX_VALUE);
+
+        current = list.add(new ItemStack(Items.DIRT), 1).getStack();
+        assertThat(current.getCount()).isEqualTo(Integer.MAX_VALUE);
+    }
+
+    @Test
+    void Test_removing_non_existent_item_should_give_back_nothing() {
+        // Arrange
+        ItemStack toAdd = new ItemStack(Items.GLASS);
+        ItemStack toRemove = new ItemStack(Items.DIRT);
+
+        // Act
+        list.add(toAdd);
+        StackListResult<ItemStack> result = list.remove(toRemove, 10);
+
+        // Assert
+        assertThat(list.size()).isEqualTo(1);
+        assertThat(result).isNull();
+    }
+
+    @Test
+    void Test_removing_half_of_an_existing_item() {
+        // Arrange
+        ItemStack toAdd1 = new ItemStack(Items.DIRT, 10);
+        ItemStack toAdd2 = new ItemStack(Items.GLASS, 10);
+        ItemStack toRemove = new ItemStack(Items.DIRT, 2);
+
+        // Act
+        list.add(toAdd1);
+        list.add(toAdd2);
+
+        StackListResult<ItemStack> result = list.remove(toRemove);
+
+        // Assert
+        assertThat(result.getStack().getItem()).isEqualTo(Items.DIRT);
+        assertThat(result.getStack().getCount()).isEqualTo(8);
+        assertThat(result.getStack().getTag()).isNull();
+        assertThat(result.getId()).isNotNull();
+        assertThat(result.getChange()).isEqualTo(-2);
+
+        assertThat(list.size()).isEqualTo(2);
+    }
+
+    @Test
+    void Test_removing_an_existing_item_completely() {
+        // Arrange
+        ItemStack toAdd1 = new ItemStack(Items.DIRT, 10);
+        ItemStack toAdd2 = new ItemStack(Items.GLASS, 10);
+        ItemStack toRemove = new ItemStack(Items.DIRT, 10);
+
+        // Act
+        list.add(toAdd1);
+        list.add(toAdd2);
+
+        StackListResult<ItemStack> result = list.remove(toRemove);
+
+        // Assert
+        assertThat(result.getStack().getItem()).isEqualTo(Items.DIRT);
+        assertThat(result.getStack().getCount()).isEqualTo(10);
+        assertThat(result.getStack().getTag()).isNull();
+        assertThat(result.getId()).isNotNull();
+        assertThat(result.getChange()).isEqualTo(-10);
+
+        assertThat(list.size()).isEqualTo(1);
+    }
+
+    @Test
+    void Test_removing_an_existing_item_with_more_than_is_available() {
+        // Arrange
+        ItemStack toAdd = new ItemStack(Items.DIRT, 10);
+        ItemStack toRemove = new ItemStack(Items.DIRT, 100);
+
+        // Act
+        list.add(toAdd);
+
+        StackListResult<ItemStack> result = list.remove(toRemove);
+
+        // Assert
+        assertThat(result.getStack().getItem()).isEqualTo(Items.DIRT);
+        assertThat(result.getStack().getCount()).isEqualTo(10);
+        assertThat(result.getStack().getTag()).isNull();
+        assertThat(result.getId()).isNotNull();
+        assertThat(result.getChange()).isEqualTo(-10);
+
+        assertThat(list.isEmpty()).isTrue();
+    }
+}

src/test/java/com/refinedmods/refinedstorage/apiimpl/util/MinecraftTest.java

@@ -0,0 +1,14 @@
+package com.refinedmods.refinedstorage.apiimpl.util;
+
+import net.minecraft.util.registry.Bootstrap;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+public abstract class MinecraftTest {
+    @BeforeAll
+    static void register() {
+        Bootstrap.register();
+    }
+}