Look for .api file in a case-insensitive manner

src/functionalTest/kotlin/kotlinx/validation/test/DefaultConfigTests.kt

@@ -89,6 +89,29 @@ internal class DefaultConfigTests : BaseKotlinGradleTest() {
         }
     }
 
+    @Test
+    fun `apiCheck should succeed when public classes match api file ignoring case`() {
+        val runner = test {
+            buildGradleKts {
+                resolve("examples/gradle/base/withPlugin.gradle.kts")
+            }
+            kotlin("AnotherBuildConfig.kt") {
+                resolve("examples/classes/AnotherBuildConfig.kt")
+            }
+            apiFile(projectName = rootProjectDir.name.toUpperCase()) {
+                resolve("examples/classes/AnotherBuildConfig.dump")
+            }
+
+            runner {
+                arguments.add(":apiCheck")
+            }
+        }
+
+        runner.build().apply {
+            assertTaskSuccess(":apiCheck")
+        }
+    }
+
     @Test
     fun `apiCheck should fail, when a public class is not in api-File`() {
         val runner = test {

src/main/kotlin/ApiCompareCompareTask.kt

@@ -11,6 +11,7 @@ import org.gradle.api.file.*
 import org.gradle.api.model.ObjectFactory
 import org.gradle.api.tasks.*
 import java.io.*
+import java.util.TreeSet
 import javax.inject.Inject
 
 open class ApiCompareCompareTask @Inject constructor(private val objects: ObjectFactory): DefaultTask() {
@@ -53,7 +54,11 @@ open class ApiCompareCompareTask @Inject constructor(private val objects: Object
 
         val subject = projectName
         val apiBuildDirFiles = mutableSetOf<RelativePath>()
-        val expectedApiFiles = mutableSetOf<RelativePath>()
+        // We use case-insensitive comparison to workaround issues with case-insensitive OSes
+        // and Gradle behaving slightly different on different platforms
+        val expectedApiFiles = TreeSet<RelativePath> { rp, rp2 ->
+            rp.toString().compareTo(rp2.toString(), true)
+        }
         objects.fileTree().from(apiBuildDir).visit { file ->
             apiBuildDirFiles.add(file.relativePath)
         }