Refactor the Sum class to be moved into the samples package.

src/main/java/space/kklochko/simple_jbdd/test_examples/Sum.java

@@ -1,8 +0,0 @@
-package space.kklochko.simple_jbdd.test_examples;
-
-public class Sum {
-    static int sum(int a, int b) {
-        return a + b;
-    }
-}
-

src/main/java/space/kklochko/simple_jbdd/test_examples/samples/Sum.java

@@ -0,0 +1,8 @@
+package space.kklochko.simple_jbdd.test_examples.samples;
+
+public class Sum {
+    public static int sum(int a, int b) {
+        return a + b;
+    }
+}
+

src/test/groovy/space/kklochko/simple_jbdd/test_examples/samples/SumSpec.groovy

@@ -1,5 +1,6 @@
-package space.kklochko.simple_jbdd.test_examples
+package space.kklochko.simple_jbdd.test_examples.samples
 
+import space.kklochko.simple_jbdd.test_examples.samples.Sum
 import spock.lang.Specification
 
 class SumSpec extends Specification {