diff --git a/src/test/java/sirius/kernel/async/BackgroundLoopSpec.groovy b/src/test/java/sirius/kernel/async/BackgroundLoopSpec.groovy
deleted file mode 100644
index 82d92413..00000000
--- a/src/test/java/sirius/kernel/async/BackgroundLoopSpec.groovy
+++ /dev/null
@@ -1,41 +0,0 @@
-/*
- * Made with all the love in the world
- * by scireum in Remshalden, Germany
- *
- * Copyright by scireum GmbH
- * http://www.scireum.de - info@scireum.de
- */
-
-package sirius.kernel.async
-
-import org.junit.jupiter.api.Tag
-import sirius.kernel.BaseSpecification
-import sirius.kernel.commons.Wait
-
-@Tag("nightly")
-class BackgroundLoopSpec extends BaseSpecification {
-
-    def "BackgroundLoop limits to max frequency"() {
-        given:
-        int currentCounter = FastTestLoop.counter
-        when:
-        Wait.seconds(10)
-        int delta = FastTestLoop.counter - currentCounter
-        then: "the background loop executed enough calls (should be 10 but we're a bit tolerant here)"
-        delta >= 8
-        and: "the background loop was limited not to execute too often (should be 10 but we're a bit tolerant here)"
-        delta <= 12
-    }
-
-    def "BackgroundLoop executes as fast as possible if loop is slow"() {
-        given:
-        int currentCounter = SlowTestLoop.counter
-        when:
-        Wait.seconds(10)
-        int delta = SlowTestLoop.counter - currentCounter
-        then: "the background loop executed enough calls (should be 5 but we're a bit tolerant here)"
-        delta >= 3
-        and: "the background loop was limited not to execute too often (should be 5 but we're a bit tolerant here)"
-        delta <= 6
-    }
-}
diff --git a/src/test/kotlin/sirius/kernel/async/BackgroundLoopTest.kt b/src/test/kotlin/sirius/kernel/async/BackgroundLoopTest.kt
new file mode 100644
index 00000000..6fd75259
--- /dev/null
+++ b/src/test/kotlin/sirius/kernel/async/BackgroundLoopTest.kt
@@ -0,0 +1,42 @@
+/*
+ * Made with all the love in the world
+ * by scireum in Remshalden, Germany
+ *
+ * Copyright by scireum GmbH
+ * http://www.scireum.de - info@scireum.de
+ */
+
+package sirius.kernel.async
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import sirius.kernel.NightlyTest
+import sirius.kernel.SiriusExtension
+import sirius.kernel.commons.Wait
+import kotlin.test.assertTrue
+
+@NightlyTest
+@ExtendWith(SiriusExtension::class)
+class BackgroundLoopSpec {
+    @Test
+    fun `BackgroundLoop limits to max frequency`() {
+        val currentCounter = FastTestLoop.counter.toInt()
+        Wait.seconds(10.0)
+        val delta = FastTestLoop.counter.toInt() - currentCounter
+        //the background loop executed enough calls (should be 10 but we're a bit tolerant here)
+        assertTrue { delta >= 8 }
+        //the background loop was limited not to execute too often (should be 10 but we're a bit tolerant here)
+        assertTrue { delta <= 12 }
+    }
+
+    @Test
+    fun `BackgroundLoop executes as fast as possible if loop is slow`() {
+        val currentCounter = SlowTestLoop.counter.toInt()
+        Wait.seconds(10.0)
+        val delta = SlowTestLoop.counter.toInt() - currentCounter
+        //the background loop executed enough calls (should be 5 but we're a bit tolerant here)
+        assertTrue { delta >= 3 }
+        //the background loop was limited not to execute too often (should be 5 but we're a bit tolerant here)
+        assertTrue { delta <= 6 }
+    }
+}