[Bug]: GenericContainer.getLogs() returns empty when container fails to start

Module

Core

Testcontainers version

2.0.1

Using the latest Testcontainers version?

Yes

Host OS

Linux Ubuntu

Host Arch

x86_64

Docker version

Client: Docker Engine - Community
 Version:           28.5.2
 API version:       1.51
 Go version:        go1.25.3
 Git commit:        ecc6942
 Built:             Wed Nov  5 14:43:10 2025
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          28.5.2
  API version:      1.51 (minimum version 1.24)
  Go version:       go1.25.3
  Git commit:       89c5e8f
  Built:            Wed Nov  5 14:43:10 2025
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v2.1.5
  GitCommit:        fcd43222d6b07379a4be9786bda52438f0dd16a1
 runc:
  Version:          1.3.3
  GitCommit:        v1.3.3-0-gd842d771
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

What happened?

I have tests for checking that my image fails under specific circumstances and gives a helpful log output.
When I try to .getLogs() from a container that failed on startup it returns an empty string.

Here is some code which reproduces the problem:

@Test
void reproduceLogsProblem() {
    Logger containerLog = LoggerFactory.getLogger( "reproduceLogsProblem" );

    try( GenericContainer<?> container = new  GenericContainer<>( DockerImageName.parse("nginx:latest")) ) {
        container.withStartupCheckStrategy(new OneShotStartupCheckStrategy())
                 .waitingFor(Wait.forLogMessage("neverhappens", 5).withStartupTimeout(Duration.ofSeconds(2)))
                 .withCommand("echo", "test log output")
                 .withLogConsumer( new Slf4jLogConsumer( containerLog ) );

        Assertions.assertThrows(ContainerLaunchException.class, container::start);
        String logOut = container.getLogs();
        Assertions.assertFalse(logOut.isEmpty(), "container.getLogs() returned nothing!");
    }
}

The .withLogConsumer( new Slf4jLogConsumer( containerLog ) ) isn't necessary for reproducing the problem but it does show that the log output happens.
When the ContainerLaunchException is thrown, it also reports the logs have content and aren't empty.

Relevant log output

Image pull policy will be performed by: DefaultPullPolicy()
Image name substitution will be performed by: DefaultImageNameSubstitutor (composite of 'ConfigurationFileImageNameSubstitutor' and 'PrefixingImageNameSubstitutor')
Testcontainers version: 2.0.1
Loaded org.testcontainers.dockerclient.UnixSocketClientProviderStrategy from ~/.testcontainers.properties, will try it first
Found Docker environment with local Unix socket (unix:///var/run/docker.sock)
Docker host IP address is localhost
Connected to docker: 
  Server Version: 28.5.2
  API Version: 1.51
  Operating System: Ubuntu 24.04.3 LTS
  Total Memory: 63499 MB
Creating container for image: testcontainers/ryuk:0.13.0
Container testcontainers/ryuk:0.13.0 is starting: 9b931acf4526223b122c2a078b009d31f613bd966b0d1b2b0ab461c84e5f4189
Container testcontainers/ryuk:0.13.0 started in PT0.287303827S
Ryuk started - will monitor and terminate Testcontainers containers on JVM exit
Checking the system...
✔︎ Docker server version should be at least 1.6.0
Creating container for image: nginx:latest
Container nginx:latest is starting: 747b4e8b469ea214bbe18455dead5672614c617080ed909e4885d87b5f8761b6
STDOUT: test log output
Could not start container
java.lang.IllegalStateException: Wait strategy failed. Container exited with code 0
	at org.testcontainers.containers.GenericContainer.tryStart(GenericContainer.java:520)
	at org.testcontainers.containers.GenericContainer.lambda$doStart$0(GenericContainer.java:341)
	at org.rnorth.ducttape.unreliables.Unreliables.retryUntilSuccess(Unreliables.java:81)
	at org.testcontainers.containers.GenericContainer.doStart(GenericContainer.java:331)
	at org.testcontainers.containers.GenericContainer.start(GenericContainer.java:317)
	at org.junit.jupiter.api.AssertThrows.assertThrows(AssertThrows.java:53)
	at org.junit.jupiter.api.AssertThrows.assertThrows(AssertThrows.java:35)
	at org.junit.jupiter.api.Assertions.assertThrows(Assertions.java:3128)
	at com.neo4j.docker.coredb.TestBasic.reproduceLogsProblem(TestBasic.java:304)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:569)
	at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:766)
	at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
	at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:156)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:147)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:86)
	at org.junit.jupiter.engine.execution.InterceptingExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(InterceptingExecutableInvoker.java:103)
	at org.junit.jupiter.engine.execution.InterceptingExecutableInvoker.lambda$invoke$0(InterceptingExecutableInvoker.java:93)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
	at org.junit.jupiter.engine.execution.InterceptingExecutableInvoker.invoke(InterceptingExecutableInvoker.java:92)
	at org.junit.jupiter.engine.execution.InterceptingExecutableInvoker.invoke(InterceptingExecutableInvoker.java:86)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$8(TestMethodTestDescriptor.java:217)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:213)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:138)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:68)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:151)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:198)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:169)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:93)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:58)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:141)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:57)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:103)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:85)
	at org.junit.platform.launcher.core.DelegatingLauncher.execute(DelegatingLauncher.java:47)
	at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:63)
	at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:66)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
	at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:231)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:55)
Caused by: org.testcontainers.containers.ContainerLaunchException: Timed out waiting for log output matching 'neverhappens'
	at org.testcontainers.containers.wait.strategy.LogMessageWaitStrategy.waitUntilReady(LogMessageWaitStrategy.java:47)
	at org.testcontainers.containers.wait.strategy.AbstractWaitStrategy.waitUntilReady(AbstractWaitStrategy.java:52)
	at org.testcontainers.containers.GenericContainer.waitUntilContainerStarted(GenericContainer.java:904)
	at org.testcontainers.containers.GenericContainer.tryStart(GenericContainer.java:487)
	... 78 more
Log output from the failed container:
test log output


org.opentest4j.AssertionFailedError: container.getLogs() returned nothing ==> 
Expected :false
Actual   :true
<Click to see difference>

Additional Information

I previously was using TestContainers version 1.20.1 and these tests worked, so something has changed between versions.

Start with GenericContainer.tryStart and the LogMessageWaitStrategy path shown in the stack trace, then trace how container logs are retained after startup fails. Use the reproduceLogsProblem example with OneShotStartupCheckStrategy and the echo command as the regression case. Done means getLogs() returns the emitted test log after ContainerLaunchException.