fix: 🐛 process glue classes distinctly

See cucumber/cucumber-jvm#2582 for context

Author: gaeljw

CHANGELOG.md

@@ -21,6 +21,8 @@ See also the [CHANGELOG](https://github.com/cucumber/cucumber-jvm/blob/master/CH
 
 ### Fixed
 
+- [Scala] Process glue classes distinctly ([#2582](https://github.com/cucumber/cucumber-jvm/pull/2582))
+
 ## [8.5.1] (2022-06-24)
 
 ### Changed

cucumber-scala/src/main/scala/io/cucumber/scala/ScalaBackend.scala

@@ -77,6 +77,7 @@ class ScalaBackend(
           .asScala
       )
       .filter(glueClass => !glueClass.isInterface)
+      .distinct
 
     // Voluntarily throw exception if not able to identify if it's a class
     val (clsClasses, objClasses) =

cucumber-scala/src/test/scala/io/cucumber/scala/ScalaBackendTest.scala

@@ -182,6 +182,32 @@ class ScalaBackendTest {
     verify(fakeLookup, never()).getInstance(any())
   }
 
+  @Test
+  def loadGlueAndBuildWorld_once_by_classpath_url(): Unit = {
+    // Load glue
+    backend.loadGlue(
+      fakeGlue,
+      List(
+        URI.create("classpath:io/cucumber/scala/steps/classes"),
+        URI.create("classpath:io/cucumber/scala/steps/classes")
+      ).asJava
+    )
+
+    assertEquals(3, backend.scalaGlueClasses.size)
+    assertTrue(
+      backend.scalaGlueClasses.toSet == Set(
+        classOf[StepsA],
+        classOf[StepsB],
+        classOf[StepsC]
+      )
+    )
+
+    verify(fakeContainer, times(3)).addClass(any())
+    verify(fakeContainer, times(1)).addClass(classOf[StepsA])
+    verify(fakeContainer, times(1)).addClass(classOf[StepsB])
+    verify(fakeContainer, times(1)).addClass(classOf[StepsC])
+  }
+
   @Test
   def loadGlueAndBuildWorld_class_incorrect_hooks_definitions(): Unit = {
     val result = Try {