diff --git a/README.md b/README.md
index e2f3ea5c..098a82e4 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@
 <a href="https://github.com/foldright/cffu/actions/workflows/ci.yaml"><img src="https://img.shields.io/github/actions/workflow/status/foldright/cffu/ci.yaml?branch=main&logo=github&logoColor=white&label=strong ci" alt="Github Workflow Build Status"></a>
 <a href="https://app.codecov.io/gh/foldright/cffu/tree/main"><img src="https://img.shields.io/codecov/c/github/foldright/cffu/main?logo=codecov&logoColor=white" alt="Codecov"></a>
 <a href="https://openjdk.java.net/"><img src="https://img.shields.io/badge/Java-8+-339933?logo=openjdk&logoColor=white" alt="Java support"></a>
-<a href="https://kotlinlang.org"><img src="https://img.shields.io/badge/Kotlin-1.5+-7F52FF.svg?logo=kotlin&logoColor=white" alt="Kotlin"></a>
+<a href="https://kotlinlang.org"><img src="https://img.shields.io/badge/Kotlin-1.6+-7F52FF.svg?logo=kotlin&logoColor=white" alt="Kotlin"></a>
 <a href="https://www.apache.org/licenses/LICENSE-2.0.html"><img src="https://img.shields.io/github/license/foldright/cffu?color=4D7A97&logo=apache" alt="License"></a>
 <a href="https://foldright.io/cffu/apidocs/"><img src="https://img.shields.io/github/release/foldright/cffu?label=javadoc&color=339933&logo=microsoft-academic&logoColor=white" alt="Javadocs"></a>
 <a href="https://foldright.io/cffu/dokka/"><img src="https://img.shields.io/github/release/foldright/cffu?label=dokka&color=339933&logo=kotlin&logoColor=white" alt="dokka"></a>
diff --git a/pom.xml b/pom.xml
index 31fc6143..1adda608 100644
--- a/pom.xml
+++ b/pom.xml
@@ -77,7 +77,7 @@
 
 		<!-- testing dependencies versions -->
 		<junit5.version>5.10.1</junit5.version>
-		<kotest.version>5.5.5</kotest.version>
+		<kotest.version>5.8.0</kotest.version>
 	</properties>
 
 	<dependencies>
diff --git a/scripts/integration_test b/scripts/integration_test
index a3e8b9fe..d9463874 100755
--- a/scripts/integration_test
+++ b/scripts/integration_test
@@ -46,9 +46,6 @@ jvu::switch_to_jdk "$default_build_jdk_version"
 
 cu::log_then_run scripts/gen_CffuApiCompatibilityTest.sh
 
-cu::head_line_echo "check kotlin compiler api version 1.5 with kotlin 1.8 "
-mvu::mvn_cmd clean test-compile -D kotlin.version=1.8.22 -D kotlin.compiler.apiVersion=1.5
-
 cu::head_line_echo "build and test with Java $default_build_jdk_version: $JAVA_HOME"
 mvu::mvn_cmd clean install
 
@@ -56,10 +53,9 @@ mvu::mvn_cmd clean install
 # test by multiply version jdks
 ########################################
 
-readonly KT_VERSION_FOR_JAVA8=1.5.0
-readonly KT_VERSION_FOR_JAVA11=1.6.0
-readonly KT_VERSION_FOR_JAVA17=1.7.0
-readonly KT_VERSION_FOR_JAVA20=1.8.22
+readonly KT_VERSION_FOR_JAVA8=1.6.0
+readonly KT_VERSION_FOR_JAVA11=1.7.0
+readonly KT_VERSION_FOR_JAVA17=1.8.0
 
 # about CI env var
 #   https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables