diff --git a/src/main/java/org/ultramine/commands/completion/DefaultCompleters.java b/src/main/java/org/ultramine/commands/completion/DefaultCompleters.java
index 7af8a11..2ee6827 100644
--- a/src/main/java/org/ultramine/commands/completion/DefaultCompleters.java
+++ b/src/main/java/org/ultramine/commands/completion/DefaultCompleters.java
@@ -14,34 +14,34 @@
 	@ArgumentCompleter(value = "player", isUsername = true)
 	public static List<String> player(String val, String[] args)
 	{
-		return getListOfStringsMatchingWord(val, MinecraftServer.getServer().getAllUsernames());
+		return filterArray(val, MinecraftServer.getServer().getAllUsernames());
 	}
 
 	@ArgumentCompleter("item")
 	public static List<String> item(String val, String[] args)
 	{
-		return getListOfStringsFromIterableMatchingWord(val, Item.itemRegistry.getKeys());
+		return filterCollection(val, Item.itemRegistry.getKeys());
 	}
 
 	@ArgumentCompleter("block")
 	public static List<String> block(String val, String[] args)
 	{
-		return getListOfStringsFromIterableMatchingWord(val, Block.blockRegistry.getKeys());
+		return filterCollection(val, Block.blockRegistry.getKeys());
 	}
 
 	@ArgumentCompleter("entity")
 	public static List<String> entity(String val, String[] args)
 	{
-		return getListOfStringsFromIterableMatchingWord(val, EntityList.func_151515_b());
+		return filterCollection(val, EntityList.func_151515_b());
 	}
 
 	@ArgumentCompleter("list")
 	public static List<String> list(String val, String[] args)
 	{
-		return getListOfStringsMatchingWord(val, args);
+		return filterArray(val, args);
 	}
 
-	public static List<String> getListOfStringsMatchingWord(String filter, String[] strings)
+	public static List<String> filterArray(String filter, String[] strings)
 	{
 		List<String> result = new ArrayList<String>();
 
@@ -54,7 +54,7 @@
 		return result;
 	}
 
-	public static List<String> getListOfStringsFromIterableMatchingWord(String filter, Iterable<String> iterable)
+	public static List<String> filterCollection(String filter, Iterable<String> iterable)
 	{
 		List<String> result = new ArrayList<String>();
 
diff --git a/src/test/groovy/org/ultramine/commands/completion/CommandCompletionHandlerTest.groovy b/src/test/groovy/org/ultramine/commands/completion/CommandCompletionHandlerTest.groovy
new file mode 100644
index 0000000..01c82c6
--- /dev/null
+++ b/src/test/groovy/org/ultramine/commands/completion/CommandCompletionHandlerTest.groovy
@@ -0,0 +1,21 @@
+package org.ultramine.commands.completion
+
+import spock.lang.Specification
+
+class CommandCompletionHandlerTest extends Specification {
+
+    def "Test completion"() {
+        setup:
+        def argumentHandler = Mock(IArgumentCompletionHandler)
+        def commandHandler = new CommandCompletionHandler()
+
+        when: "Add argument handler to command handler"
+        commandHandler.addNextArgument(argumentHandler, "a", "b")
+
+        and: "Get completion for first argument"
+        commandHandler.getCompletionOptions("as")
+
+        then: "Argument handler is called"
+        1 * argumentHandler.handleCompletion("as", "a", "b")
+    }
+}