Make methods running before application start public

settings.gradle

@@ -11,4 +11,5 @@ include(
         ":streams-bootstrap-test",
         ":streams-bootstrap-large-messages",
         ":streams-bootstrap-cli",
+        ":streams-bootstrap-cli-test",
 )

streams-bootstrap-cli-test/build.gradle.kts

@@ -0,0 +1,6 @@
+description = "Utils for testing your Kafka Streams Application"
+
+dependencies {
+    api(project(":streams-bootstrap-test"))
+    api(project(":streams-bootstrap-cli"))
+}

streams-bootstrap-cli-test/lombok.config

@@ -0,0 +1,3 @@
+# This file is generated by the 'io.freefair.lombok' Gradle plugin
+config.stopBubbling = true
+lombok.addLombokGeneratedAnnotation = true

streams-bootstrap-cli-test/src/main/java/com/bakdata/kafka/CapturingUncaughtExceptionHandler.java

@@ -0,0 +1,38 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2025 bakdata
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.bakdata.kafka;
+
+import java.lang.Thread.UncaughtExceptionHandler;
+import lombok.Getter;
+
+@Getter
+public class CapturingUncaughtExceptionHandler implements UncaughtExceptionHandler {
+    private Throwable lastException;
+
+    @Override
+    public void uncaughtException(final Thread t, final Throwable e) {
+        this.lastException = e;
+    }
+}

streams-bootstrap-cli-test/src/main/java/com/bakdata/kafka/TestApplicationHelper.java

@@ -0,0 +1,101 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2025 bakdata
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.bakdata.kafka;
+
+import com.bakdata.fluent_kafka_streams_tests.TestTopology;
+import java.lang.Thread.UncaughtExceptionHandler;
+import lombok.NonNull;
+import lombok.RequiredArgsConstructor;
+import lombok.experimental.Delegate;
+import picocli.CommandLine;
+
+@RequiredArgsConstructor
+public final class TestApplicationHelper {
+
+    @Delegate
+    private final @NonNull TestTopologyFactory topologyFactory;
+
+    public static TestApplicationHelper withoutSchemaRegistry() {
+        return new TestApplicationHelper(TestTopologyFactory.withoutSchemaRegistry());
+    }
+
+    public static TestApplicationHelper withSchemaRegistry() {
+        return new TestApplicationHelper(TestTopologyFactory.withSchemaRegistry());
+    }
+
+    public static TestApplicationHelper withSchemaRegistry(final String schemaRegistryUrl) {
+        return new TestApplicationHelper(TestTopologyFactory.withSchemaRegistry(schemaRegistryUrl));
+    }
+
+    public Thread runApplication(final KafkaStreamsApplication<? extends StreamsApp> app) {
+        this.configure(app);
+        new CommandLine(app); // initialize all mixins
+        app.onApplicationStart();
+        final Thread thread = new Thread(app);
+        final UncaughtExceptionHandler handler = new CapturingUncaughtExceptionHandler();
+        thread.setUncaughtExceptionHandler(handler);
+        thread.start();
+        return thread;
+    }
+
+    public ConsumerGroupVerifier verify(final KafkaStreamsApplication<? extends StreamsApp> app) {
+        this.configure(app);
+        final KafkaEndpointConfig endpointConfig = app.getEndpointConfig();
+        final KafkaTestClient testClient = new KafkaTestClient(endpointConfig);
+        try (final ConfiguredStreamsApp<? extends StreamsApp> configuredApp = app.createConfiguredApp()) {
+            final String uniqueAppId = configuredApp.getUniqueAppId();
+            return new ConsumerGroupVerifier(uniqueAppId, testClient::admin);
+        }
+    }
+
+    public ConfiguredStreamsApp<? extends StreamsApp> createConfiguredApp(
+            final KafkaStreamsApplication<? extends StreamsApp> app) {
+        this.configure(app);
+        app.prepareRun();
+        return app.createConfiguredApp();
+    }
+
+    public <K, V> TestTopology<K, V> createTopology(final KafkaStreamsApplication<? extends StreamsApp> app) {
+        final ConfiguredStreamsApp<? extends StreamsApp> configuredApp = this.createConfiguredApp(app);
+        return this.<K, V>createTopology(configuredApp);
+    }
+
+    public <K, V> TestTopology<K, V> createTopologyExtension(final KafkaStreamsApplication<? extends StreamsApp> app) {
+        final ConfiguredStreamsApp<? extends StreamsApp> configuredApp = this.createConfiguredApp(app);
+        return this.<K, V>createTopologyExtension(configuredApp);
+    }
+
+    public KafkaTestClient newTestClient(final String bootstrapServers) {
+        return new KafkaTestClient(KafkaEndpointConfig.builder()
+                .bootstrapServers(bootstrapServers)
+                .schemaRegistryUrl(this.getSchemaRegistryUrl())
+                .build());
+    }
+
+    public void configure(final KafkaStreamsApplication<? extends StreamsApp> app) {
+        app.setSchemaRegistryUrl(this.getSchemaRegistryUrl());
+    }
+
+}

streams-bootstrap-cli/build.gradle.kts

@@ -18,6 +18,7 @@ dependencies {
     testImplementation(group = "org.mockito", name = "mockito-core", version = mockitoVersion)
     testImplementation(group = "org.mockito", name = "mockito-junit-jupiter", version = mockitoVersion)
     testImplementation(testFixtures(project(":streams-bootstrap-core")))
+    testImplementation(project(":streams-bootstrap-cli-test"))
     testImplementation(group = "com.ginsberg", name = "junit5-system-exit", version = "1.1.2")
     val confluentVersion: String by project
     testImplementation(group = "io.confluent", name = "kafka-streams-avro-serde", version = confluentVersion)

streams-bootstrap-cli/src/test/java/com/bakdata/kafka/integration/RunStreamsAppTest.java

@@ -31,6 +31,7 @@
 import com.bakdata.kafka.KafkaTestClient;
 import com.bakdata.kafka.SenderBuilder.SimpleProducerRecord;
 import com.bakdata.kafka.SimpleKafkaStreamsApplication;
+import com.bakdata.kafka.TestApplicationHelper;
 import com.bakdata.kafka.TestTopologyFactory;
 import com.bakdata.kafka.test_applications.Mirror;
 import java.nio.file.Path;
@@ -57,8 +58,7 @@ void shouldRunApp() {
             app.setKafkaConfig(TestTopologyFactory.createStreamsTestConfig(this.stateDir));
             app.setInputTopics(List.of(input));
             app.setOutputTopic(output);
-            // run in Thread because the application blocks indefinitely
-            new Thread(app).start();
+            TestApplicationHelper.withoutSchemaRegistry().runApplication(app);
             testClient.send()
                     .with(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class)
                     .with(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class)

streams-bootstrap-cli/src/test/java/com/bakdata/kafka/integration/StreamsCleanUpTest.java

@@ -31,6 +31,7 @@
 import com.bakdata.kafka.KafkaTestClient;
 import com.bakdata.kafka.SenderBuilder.SimpleProducerRecord;
 import com.bakdata.kafka.SimpleKafkaStreamsApplication;
+import com.bakdata.kafka.TestApplicationHelper;
 import com.bakdata.kafka.TestTopologyFactory;
 import com.bakdata.kafka.test_applications.WordCount;
 import com.bakdata.kafka.util.ImprovedAdminClient;
@@ -155,8 +156,7 @@ private void runAppAndClose(final KafkaStreamsApplication<?> app) {
     }
 
     private void runApp(final KafkaStreamsApplication<?> app) {
-        // run in Thread because the application blocks indefinitely
-        new Thread(app).start();
+        TestApplicationHelper.withoutSchemaRegistry().runApplication(app);
         // Wait until stream application has consumed all data
         this.awaitProcessing(app.createExecutableApp());
     }