JRuby call Method from Java

I try to call a Ruby method from Java

test_a.rb:

module Test
    def Test.Test_1
        stmt = "Test 1"
        stmt
    end
end

test.rb which includes the test_a.rb file

require_relative "./test/test_a.rb"

Java-Code

package com.example;

import java.util.ArrayList;

import org.jruby.embed.LocalContextScope;
import org.jruby.embed.LocalVariableBehavior;
import org.jruby.embed.PathType;
import org.jruby.embed.ScriptingContainer;

public class test_ruby {
    public static void main(String[] args) {
        try {
            ScriptingContainer jruby = new ScriptingContainer(LocalContextScope.THREADSAFE, LocalVariableBehavior.GLOBAL);
            ArrayList<String> loadPath = new ArrayList<>();
            loadPath.add("C:\\Users\\nikol\\Downloads\\starter\\ruby\\base");
            jruby.setLoadPaths(loadPath);
            System.out.println("Load Files");
            jruby.runScriptlet(PathType.RELATIVE, "ruby\\\\base\\test\\lib\\test.rb");
            String returnValue = jruby.runRubyMethod(String.class, null, "Test.Test_1");
            System.out.println(returnValue);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

The only output a managed is an error

Load Files
org.jruby.embed.InvokeFailedException: org.jruby.exceptions.NoMethodError: (NoMethodError) undefined method `Test.Test_1' for nil:NilClass
        at org.jruby.embed.internal.EmbedRubyObjectAdapterImpl.doInvokeMethod(EmbedRubyObjectAdapterImpl.java:251)
        at org.jruby.embed.internal.EmbedRubyObjectAdapterImpl.runRubyMethod(EmbedRubyObjectAdapterImpl.java:198)
        at org.jruby.embed.ScriptingContainer.runRubyMethod(ScriptingContainer.java:1579)
        at com.example.test_ruby.main(test_ruby.java:19)
Caused by: org.jruby.exceptions.NoMethodError: (NoMethodError) undefined method `Test.Test_1' for nil:NilClass

What is the correct way, to call this one method from Java?

I converted Test.Test_1 into a class, like all other examples. That worked for me.