Add the Test class as ABC.

src/main/java/space/kklochko/simple_jbdd/annotations/Given.java

@@ -0,0 +1,13 @@
+package space.kklochko.simple_jbdd.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+public @interface Given {
+    String value() default "Given";
+}
+

src/main/java/space/kklochko/simple_jbdd/annotations/Then.java

@@ -0,0 +1,13 @@
+package space.kklochko.simple_jbdd.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+public @interface Then {
+    String value() default "Then";
+}
+

src/main/java/space/kklochko/simple_jbdd/annotations/When.java

@@ -0,0 +1,13 @@
+package space.kklochko.simple_jbdd.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+public @interface When {
+    String value() default "When";
+}
+

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/main/java/space/kklochko/simple_jbdd/test_examples/tests/SimpleFailedThenTest.java

@@ -0,0 +1,12 @@
+package space.kklochko.simple_jbdd.test_examples.tests;
+
+import space.kklochko.simple_jbdd.annotations.Then;
+import space.kklochko.simple_jbdd.tests.Test;
+
+public class SimpleFailedThenTest extends Test {
+    @Then
+    public void check() {
+        assert 30 == 10 + 20 + 1;
+    }
+}
+

src/main/java/space/kklochko/simple_jbdd/test_examples/tests/SimpleGivenWhenThenTest.java

@@ -0,0 +1,30 @@
+package space.kklochko.simple_jbdd.test_examples.tests;
+
+import space.kklochko.simple_jbdd.annotations.Given;
+import space.kklochko.simple_jbdd.annotations.Then;
+import space.kklochko.simple_jbdd.annotations.When;
+import space.kklochko.simple_jbdd.test_examples.samples.Sum;
+import space.kklochko.simple_jbdd.tests.Test;
+
+public class SimpleGivenWhenThenTest extends Test {
+    private Sum sum;
+    private int a;
+    private int b;
+
+    @Given
+    void setup() {
+        sum = new Sum();
+    }
+
+    @When
+    void trigger() {
+        a = 10;
+        b = 20;
+    }
+
+    @Then
+    void check() {
+        assert 30 == sum.sum(a, b);
+    }
+}
+

src/main/java/space/kklochko/simple_jbdd/test_examples/tests/SimpleThenTest.java

@@ -0,0 +1,12 @@
+package space.kklochko.simple_jbdd.test_examples.tests;
+
+import space.kklochko.simple_jbdd.annotations.Then;
+import space.kklochko.simple_jbdd.tests.Test;
+
+public class SimpleThenTest extends Test {
+    @Then
+    public void check() {
+        assert 30 == 10 + 20;
+    }
+}
+

src/main/java/space/kklochko/simple_jbdd/tests/Test.java

@@ -0,0 +1,6 @@
+package space.kklochko.simple_jbdd.tests;
+
+public abstract class Test {
+
+}
+

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 {