Make it an error when there is no "isShould" and "describe" block

robospec/src/commonMain/kotlin/io/github/takahirom/robospec/DescribeBehaviors.kt

@@ -119,6 +119,11 @@ class BehaviorsTreeBuilder<T>(private val parentDescription: String = "") {
         children.add(TestNode.ItShould(description) { describedBehavior -> action(describedBehavior) })
     }
 
-    fun build(name: String): TestNode.Describe<T> = TestNode.Describe(name, children)
+    fun build(name: String): TestNode.Describe<T> {
+        if (children.all { it is TestNode.DoIt }) {
+            throw IllegalStateException("No itShould or describe block found for $name. Please add itShould or describe block, otherwise, it will not be executed.")
+        }
+        return TestNode.Describe(name, children)
+    }
 }
 

robospec/src/jvmTest/kotlin/io/github/takahirom/robospec/DSLBehaviorTest.kt

@@ -4,12 +4,11 @@ import kotlinx.coroutines.runBlocking
 import org.junit.Test
 
 class DSLBehaviorTest {
-    @Test
-    fun `when just using describe behavior with doIt it should not run`() {
+    @Test(expected = IllegalStateException::class)
+    fun `when just using describe behavior with doIt it should be error`() {
         runBlocking {
             describeBehaviors<Unit>("root") {
                 doIt {
-                    error("should not be called")
                 }
             }.forEach { it.execute(Unit) }
         }