Updates MockBukkit, and fixes some test-related issues

Fixes JUnit 5's After being used instead of AfterEach
Fixes a potential NullPointerException when tearing down GateLayoutTest

pom.xml

@@ -66,8 +66,8 @@
         </dependency>
         <dependency>
             <groupId>com.github.seeseemelk</groupId>
-            <artifactId>MockBukkit-v1.18</artifactId>
-            <version>2.85.2</version>
+            <artifactId>MockBukkit-v1.20</artifactId>
+            <version>3.78.0</version>
             <scope>test</scope>
         </dependency>
         <dependency>

src/main/java/net/knarcraft/stargate/command/ConfigTabCompleter.java

@@ -65,23 +65,22 @@ public class ConfigTabCompleter implements TabCompleter {
     private List<String> getPossibleOptionValues(@NotNull ConfigOption selectedOption,
                                                  @NotNull String typedText) {
         switch (selectedOption) {
-            case LANGUAGE:
+            case LANGUAGE -> {
                 //Return available languages
                 return filterMatchingStartsWith(languages, typedText);
-            case GATE_FOLDER:
-            case PORTAL_FOLDER:
-            case DEFAULT_GATE_NETWORK:
+            }
+            case GATE_FOLDER, PORTAL_FOLDER, DEFAULT_GATE_NETWORK -> {
                 //Just return the default value as most values should be possible
                 if (typedText.trim().isEmpty()) {
                     return List.of((String) selectedOption.getDefaultValue());
                 } else {
                     return new ArrayList<>();
                 }
-            case MAIN_SIGN_COLOR:
-            case HIGHLIGHT_SIGN_COLOR:
-            case FREE_GATES_COLOR:
+            }
+            case MAIN_SIGN_COLOR, HIGHLIGHT_SIGN_COLOR, FREE_GATES_COLOR -> {
                 //Return all colors
                 return filterMatchingStartsWith(chatColors, typedText);
+            }
         }
 
         //If the config value is a boolean, show the two boolean values

src/test/java/net/knarcraft/stargate/BlockLocationTest.java

@@ -4,7 +4,7 @@ import be.seeseemelk.mockbukkit.MockBukkit;
 import be.seeseemelk.mockbukkit.WorldMock;
 import net.knarcraft.stargate.container.BlockLocation;
 import org.bukkit.Material;
-import org.junit.After;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
@@ -19,7 +19,7 @@ public class BlockLocationTest {
         mockWorld = new WorldMock(Material.DIRT, 5);
     }
 
-    @After
+    @AfterEach
     public void tearDown() {
         MockBukkit.unmock();
     }

src/test/java/net/knarcraft/stargate/portal/GateLayoutTest.java

@@ -9,6 +9,7 @@ import net.knarcraft.stargate.portal.property.gate.Gate;
 import net.knarcraft.stargate.portal.property.gate.GateHandler;
 import net.knarcraft.stargate.portal.property.gate.GateLayout;
 import org.bukkit.Material;
+import org.jetbrains.annotations.Nullable;
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -39,7 +40,10 @@ public class GateLayoutTest {
 
     @AfterAll
     public static void tearDown() {
-        MockBukkit.getMock().getPluginManager().disablePlugins();
+        @Nullable ServerMock mock = MockBukkit.getMock();
+        if (mock != null) {
+            mock.getPluginManager().disablePlugins();
+        }
         MockBukkit.unmock();
     }