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common_functional_options.md

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Basic Options

WithExposedPorts

If you need to expose additional ports from the container, you can use testcontainers.WithExposedPorts. For example:

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithExposedPorts("8080/tcp", "9090/tcp"))
WithEnv

If you need to either pass additional environment variables to a container or override them, you can use testcontainers.WithEnv for example:

ctr, err = mymodule.Run(ctx, "docker.io/myservice:1.2.3", testcontainers.WithEnv(map[string]string{"FOO": "BAR"}))
WithWaitStrategy

If you need to set a different wait strategy for the container, you can use testcontainers.WithWaitStrategy with a valid wait strategy.

!!!info The default deadline for the wait strategy is 60 seconds.

WithWaitStrategyAndDeadline

At the same time, it's possible to set a wait strategy and a custom deadline with testcontainers.WithWaitStrategyAndDeadline.

WithAdditionalWaitStrategy

If you need to add a wait strategy to the existing wait strategy, you can use testcontainers.WithAdditionalWaitStrategy.

!!!info The default deadline for the wait strategy is 60 seconds.

WithAdditionalWaitStrategyAndDeadline

At the same time, it's possible to add a wait strategy and a custom deadline with testcontainers.WithAdditionalWaitStrategyAndDeadline.

WithEntrypoint

If you need to completely replace the container's entrypoint, you can use testcontainers.WithEntrypoint. For example:

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithEntrypoint("/bin/sh", "-c", "echo hello"))
WithEntrypointArgs

If you need to append commands to the container's entrypoint, you can use testcontainers.WithEntrypointArgs. For example:

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithEntrypointArgs("echo", "hello"))
WithCmd

If you need to completely replace the container's command, you can use testcontainers.WithCmd. For example:

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithCmd("echo", "hello"))
WithCmdArgs

If you need to append commands to the container's command, you can use testcontainers.WithCmdArgs. For example:

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithCmdArgs("echo", "hello"))
WithLabels

If you need to add Docker labels to the container, you can use testcontainers.WithLabels. For example:

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithLabels(map[string]string{
        "environment": "testing",
        "project":     "myapp",
    }))

Lifecycle Options

WithLifecycleHooks

If you need to set the lifecycle hooks for the container, you can use testcontainers.WithLifecycleHooks, which replaces the existing lifecycle hooks with the new ones.

WithAdditionalLifecycleHooks

You can also use testcontainers.WithAdditionalLifecycleHooks, which appends the new lifecycle hooks to the existing ones.

WithStartupCommand

Testcontainers exposes the WithStartupCommand(e ...Executable) option to run arbitrary commands in the container right after it's started.

!!!info To better understand how this feature works, please read the Create containers: Lifecycle Hooks documentation.

It also exports an Executable interface, defining the following methods:

  • AsCommand(), which returns a slice of strings to represent the command and positional arguments to be executed in the container;
  • Options(), which returns the slice of functional options with the Docker's ExecConfigs used to create the command in the container (the working directory, environment variables, user executing the command, etc) and the possible output format (Multiplexed).

You could use this feature to run a custom script, or to run a command that is not supported by the module right after the container is started.

WithAfterReadyCommand

Testcontainers exposes the WithAfterReadyCommand(e ...Executable) option to run arbitrary commands in the container right after it's ready, which happens when the defined wait strategies have finished with success.

!!!info To better understand how this feature works, please read the Create containers: Lifecycle Hooks documentation.

It leverages the Executable interface to represent the command and positional arguments to be executed in the container.

You could use this feature to run a custom script, or to run a command that is not supported by the module right after the container is ready.

Files & Mounts Options

WithFiles

If you need to copy files into the container, you can use testcontainers.WithFiles. For example:

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithFiles([]testcontainers.ContainerFile{
        {
            HostFilePath:      "/path/to/local/file.txt",
            ContainerFilePath: "/container/file.txt",
            FileMode:          0o644,
        },
    }))

This option allows you to copy files from the host into the container at creation time.

WithMounts

If you need to add volume mounts to the container, you can use testcontainers.WithMounts. For example:

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithMounts([]testcontainers.ContainerMount{
        {
            Source: testcontainers.GenericVolumeMountSource{Name: "appdata"},
            Target: "/app/data",
        },
    }))
WithTmpfs

If you need to add tmpfs mounts to the container, you can use testcontainers.WithTmpfs. For example:

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithTmpfs(map[string]string{
        "/tmp": "size=100m",
        "/run": "size=100m",
    }))
WithImageMount

Since Docker v28, it's possible to mount an image to a container, passing the source image name, the relative subpath to mount in that image, and the mount point in the target container.

This option validates that the subpath is a relative path, raising an error otherwise.

Image Mount inside_block:mountImage

In the code above, which mounts the directory in which Ollama models are stored, the targetImage is the name of the image containing the models (an Ollama image where the models are already pulled).

!!!warning Using this option fails the creation of the container if the underlying container runtime does not support the image mount feature.

Build Options

WithDockerfile

Testcontainers exposes the testcontainers.WithDockerfile option to build a container from a Dockerfile. The functional option receives a testcontainers.FromDockerfile struct that is applied to the container request before starting the container. As a result, the container is built and started in one go.

df := testcontainers.FromDockerfile{
	Context:    ".",
	Dockerfile: "Dockerfile",
	Repo:       "testcontainers",
	Tag:        "latest",
	BuildArgs:  map[string]*string{"ARG1": nil, "ARG2": nil},
}   

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", testcontainers.WithDockerfile(df))

Logging Options

WithLogConsumers

If you need to consume the logs of the container, you can use testcontainers.WithLogConsumers with a valid log consumer. An example of a log consumer is the following:

type TestLogConsumer struct {
	Msgs []string
}

func (g *TestLogConsumer) Accept(l Log) {
	g.Msgs = append(g.Msgs, string(l.Content))
}
WithLogConsumerConfig

If you need to set the log consumer config for the container, you can use testcontainers.WithLogConsumerConfig. This option completely replaces the existing log consumer config, including the log consumers and the log production options.

WithLogger

If you need to either pass logger to a container, you can use testcontainers.WithLogger.

!!!info Consider calling this before other "With" functions as these may generate logs.

In this example we also use the testcontainers-go log.TestLogger, which writes to the passed in testing.TB using Logf. The result is that we capture all logging from the container into the test context meaning its hidden behind go test -v and is associated with the relevant test, providing the user with useful context instead of appearing out of band.

func TestHandler(t *testing.T) {
    logger := log.TestLogger(t)
    ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", testcontainers.WithLogger(logger))
    CleanupContainer(t, ctr)
    require.NoError(t, err)
    // Do something with container.
}

Please read the Following Container Logs documentation for more information about creating log consumers.

Image Options

WithAlwaysPull

If you need to pull the image before starting the container, you can use testcontainers.WithAlwaysPull().

WithImageSubstitutors

In more locked down / secured environments, it can be problematic to pull images from Docker Hub and run them without additional precautions.

An image name substitutor converts a Docker image name, as may be specified in code, to an alternative name. This is intended to provide a way to override image names, for example to enforce pulling of images from a private registry.

Testcontainers for Go exposes an interface to perform this operation: ImageSubstitutor, and a No-operation implementation to be used as reference for custom implementations:

Image Substitutor Interface inside_block:imageSubstitutor Noop Image Substitutor inside_block:noopImageSubstitutor

Using the WithImageSubstitutors options, you could define your own substitutions to the container images. E.g. adding a prefix to the images so that they can be pulled from a Docker registry other than Docker Hub. This is the usual mechanism for using Docker image proxies, caches, etc.

WithImagePlatform

If you need to set the platform for a container, you can use testcontainers.WithImagePlatform(platform string).

Networking Options

WithNetwork

By default, the container is started in the default Docker network. If you want to use an already existing Docker network you created in your code, you can use the network.WithNetwork(aliases []string, nw *testcontainers.DockerNetwork) option, which receives an alias as parameter and your network, attaching the container to it, and setting the network alias for that network.

In the case you need to retrieve the network name, you can simply read it from the struct's Name field. E.g. nw.Name.

!!!warning This option is not checking whether the network exists or not. If you use a network that doesn't exist, the container will start in the default Docker network, as in the default behavior.

WithNetworkByName

If you want to attach your containers to an already existing Docker network by its name, you can use the network.WithNetworkName(aliases []string, networkName string) option, which receives an alias as parameter and the network name, attaching the container to it, and setting the network alias for that network.

!!!warning In case the network name is bridge, no aliases are set. This is because network-scoped alias is supported only for containers in user defined networks.

WithBridgeNetwork

If you want to attach your containers to the bridge network, you can use the network.WithBridgeNetwork() option.

!!!warning The bridge network is the default network for Docker. It's not a user defined network, so it doesn't support network-scoped aliases.

WithNewNetwork

If you want to attach your containers to a throw-away network, you can use the network.WithNewNetwork(ctx context.Context, aliases []string, opts ...network.NetworkCustomizer) option, which receives an alias as parameter, creating the new network with a random name, attaching the container to it, and setting the network alias for that network.

In the case you need to retrieve the network name, you can use the Networks(ctx) method of the Container interface, right after it's running, which returns a slice of strings with the names of the networks where the container is attached.

Advanced Options

WithHostPortAccess

If you need to access a port that is already running in the host, you can use testcontainers.WithHostPortAccess for example:

ctr, err = mymodule.Run(ctx, "docker.io/myservice:1.2.3", testcontainers.WithHostPortAccess(8080))

To understand more about this feature, please read the Exposing host ports to the container documentation.

WithConfigModifier

If you need an advanced configuration for the container, modifying the container's configuration, you can use the testcontainers.WithConfigModifier option, which gives access to the underlying Docker's Config type.

WithHostConfigModifier

If you need an advanced configuration for the container, modifying the container's host configuration, you can use the testcontainers.WithHostConfigModifier option, which gives access to the underlying Docker's HostConfig type.

WithEndpointSettingsModifier

If you need an advanced configuration for the container, modifying the container's endpoint settings, you can use the testcontainers.WithEndpointSettingsModifier option, which gives access to the underlying Docker's EndpointSettings type.

CustomizeRequest

This option will merge the customized request into the module's own ContainerRequest.

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3",
    /* Other module options */
    testcontainers.CustomizeRequest(testcontainers.GenericContainerRequest{
        ContainerRequest: testcontainers.ContainerRequest{
            Cmd: []string{"-c", "log_statement=all"},
        },
    }),
)

The above example is updating the predefined command of the image, appending them to the module's command.

!!!info This can't be used to replace the command, only to append options.

WithName

If you need to set the name of the container, you can use the testcontainers.WithName option.

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithName("my-container-name"),
)

!!!warning This option is not checking whether the container name is already in use. If you use a name that is already in use, an error is returned. At the same time, we discourage using this option as it might lead to unexpected behavior, but we understand that in some cases it might be useful.

WithNoStart

If you need to prevent the container from being started after creation, you can use the testcontainers.WithNoStart option.

WithProvider

If you need specify which provider to use to run the container, you can use the testcontainers.WithProvider option. Currently only docker or podman are supported.

Experimental Options

WithReuseByName

This option marks a container to be reused if it exists or create a new one if it doesn't. With the current implementation, the container name must be provided to identify the container to be reused.

ctr, err := mymodule.Run(ctx, "docker.io/myservice:1.2.3", 
    testcontainers.WithReuseByName("my-container-name"),
)

!!!warning Reusing a container is experimental and the API is subject to change for a more robust implementation that is not based on container names.