diff --git a/core/build.gradle b/core/build.gradle
index 11372168575..f5ecd2a7097 100644
--- a/core/build.gradle
+++ b/core/build.gradle
@@ -126,7 +126,7 @@ dependencies {
     }
 
     // TestNG
-    testImplementation libs.testng
+    testRuntimeOnly libs.junit.testng.engine
 
     // JUnit Pioneer
     testImplementation libs.junit.pioneer
@@ -203,34 +203,6 @@ testing.suites {
 }
 tasks.check.dependsOn testing.suites.testStreaming
 
-// Run the test cases based on reactive-streams-tck only with non-flaky mode
-if (rootProject.findProperty('flakyTests') != 'true') {
-    testing.suites {
-        testNg(JvmTestSuite) {
-            useTestNG()
-
-            targets.configureEach {
-                testTask.configure {
-
-                    project.ext.configureCommonTestSettings(it)
-                    include '/com/linecorp/armeria/**/common/**'
-                    dependsOn tasks.copyShadedTestClasses
-                    scanForTestClasses = false
-                    testClassesDirs = tasks.shadedTest.testClassesDirs
-                    classpath = testClassesDirs
-                    doFirst {
-                        classpath += project.files(configurations.shadedJarTestRuntime.resolve())
-                    }
-                }
-            }
-            dependencies {
-                runtimeOnly libs.junit.testng.engine
-            }
-        }
-    }
-    tasks.check.dependsOn testing.suites.testNg
-}
-
 if (tasks.findByName('trimShadedJar')) {
     tasks.trimShadedJar.configure {
         // Keep all classes under com.linecorp.armeria, except the internal ones.
diff --git a/core/src/test/java/com/linecorp/armeria/client/Http2HeadersLimitTest.java b/core/src/test/java/com/linecorp/armeria/client/Http2HeadersLimitTest.java
index 0441d605164..52852b71454 100644
--- a/core/src/test/java/com/linecorp/armeria/client/Http2HeadersLimitTest.java
+++ b/core/src/test/java/com/linecorp/armeria/client/Http2HeadersLimitTest.java
@@ -21,7 +21,8 @@
 
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
-import org.testng.util.Strings;
+
+import com.google.common.base.Strings;
 
 import com.linecorp.armeria.client.logging.LoggingClient;
 import com.linecorp.armeria.common.Flags;
diff --git a/core/src/test/java/com/linecorp/armeria/common/DefaultSplitHttpResponseTest.java b/core/src/test/java/com/linecorp/armeria/common/DefaultSplitHttpResponseTest.java
index 9128203f208..fd9dfae8321 100644
--- a/core/src/test/java/com/linecorp/armeria/common/DefaultSplitHttpResponseTest.java
+++ b/core/src/test/java/com/linecorp/armeria/common/DefaultSplitHttpResponseTest.java
@@ -30,7 +30,8 @@
 import org.junit.jupiter.api.extension.RegisterExtension;
 import org.reactivestreams.Subscriber;
 import org.reactivestreams.Subscription;
-import org.testng.util.Strings;
+
+import com.google.common.base.Strings;
 
 import com.linecorp.armeria.client.ResponseTimeoutException;
 import com.linecorp.armeria.client.WebClient;
diff --git a/dependencies.toml b/dependencies.toml
index a0f46a6d5e9..2d3a0021316 100644
--- a/dependencies.toml
+++ b/dependencies.toml
@@ -135,7 +135,6 @@ spring6 = "6.1.3"
 spring-boot2 = "2.7.18"
 spring-boot3 = "3.2.2"
 testcontainers = "1.19.1"
-testng = "7.5.1"
 thrift09 = { strictly = "0.9.3-1" }
 thrift012 = { strictly = "0.12.0" }
 thrift013 = { strictly = "0.13.0" }
@@ -752,7 +751,7 @@ version.ref = "junit-pioneer"
 
 [libraries.junit-testng-engine]
 module = "org.junit.support:testng-engine"
-version = "1.0.4"
+version = "1.0.5"
 
 [libraries.jwt]
 module = "com.auth0:java-jwt"
@@ -1249,11 +1248,6 @@ module = "org.testcontainers:consul"
 [libraries.testcontainers-junit-jupiter]
 module = "org.testcontainers:junit-jupiter"
 
-# jdk 11 is required from testng version 7.6
-[libraries.testng]
-module = "org.testng:testng"
-version.ref = "testng"
-
 [libraries.thrift09]
 module = "org.apache.thrift:libthrift"
 version.ref = "thrift09"
diff --git a/grpc/src/test/java/com/linecorp/armeria/internal/common/grpc/HttpDeframerTckTest.java b/grpc/src/test/java/com/linecorp/armeria/internal/common/grpc/HttpDeframerTckTest.java
index b741173b96f..7fe0c786f6d 100644
--- a/grpc/src/test/java/com/linecorp/armeria/internal/common/grpc/HttpDeframerTckTest.java
+++ b/grpc/src/test/java/com/linecorp/armeria/internal/common/grpc/HttpDeframerTckTest.java
@@ -40,6 +40,7 @@
 import reactor.core.publisher.Flux;
 
 @Test
+@Ignore
 public class HttpDeframerTckTest extends PublisherVerification<DeframedMessage> {
 
     private static final TransportStatusListener noopListener = (status, metadata) -> {};
diff --git a/kotlin/build.gradle.kts b/kotlin/build.gradle.kts
index a7c3eedaeaf..048cb980455 100644
--- a/kotlin/build.gradle.kts
+++ b/kotlin/build.gradle.kts
@@ -16,34 +16,3 @@ tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
         freeCompilerArgs += listOf("-opt-in=kotlin.RequiresOptIn")
     }
 }
-
-testing {
-    suites {
-        @Suppress("UNUSED_VARIABLE")
-        val testNg by registering(JvmTestSuite::class) {
-            useTestNG()
-
-            targets {
-                all {
-                    testTask.configure {
-                        group = "Verification"
-                        description = "Runs the TestNG unit tests"
-                        dependsOn(tasks.copyShadedTestClasses)
-                        val shadedTestTask = tasks.shadedTest.get()
-                        testClassesDirs = shadedTestTask.testClassesDirs
-                        classpath = shadedTestTask.testClassesDirs
-                        doFirst {
-                            classpath += project.files(configurations.shadedJarTestRuntime.get().resolve())
-                        }
-                    }
-                }
-            }
-
-            dependencies {
-                runtimeOnly(libs.junit.testng.engine)
-            }
-        }
-    }
-}
-
-tasks.check { dependsOn(testing.suites.named("testNg")) }