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Neo4j

Since testcontainers-go v0.20.0

Introduction

The Testcontainers module for Neo4j, the leading graph platform.

Adding this module to your project dependencies

Please run the following command to add the Neo4j module to your Go dependencies:

go get github.com/testcontainers/testcontainers-go/modules/neo4j

Usage example

Running Neo4j as a single-instance server, with the APOC plugin enabled:

ctx := context.Background()

testPassword := "letmein!"

neo4jContainer, err := neo4j.RunContainer(ctx,
    testcontainers.WithImage("docker.io/neo4j:4.4"),
    neo4j.WithAdminPassword(testPassword),
    neo4j.WithLabsPlugin(neo4j.Apoc),
    neo4j.WithNeo4jSetting("dbms.tx_log.rotation.size", "42M"),
)
if err != nil {
    log.Fatalf("failed to start container: %s", err)
}

// Clean up the container
defer func() {
    if err := neo4jContainer.Terminate(ctx); err != nil {
        log.Fatalf("failed to terminate container: %s", err)
    }
}()

Module Reference

The Neo4j module exposes one entrypoint function to create the Neo4j container, and this function receives two parameters:

func RunContainer(ctx context.Context, opts ...testcontainers.ContainerCustomizer) (*Neo4jContainer, error)
  • context.Context, the Go context.
  • testcontainers.ContainerCustomizer, a variadic argument for passing options.

Container Ports

These are the ports used by the Neo4j container:

defaultBoltPort  = "7687"
defaultHttpPort  = "7474"
defaultHttpsPort = "7473"

Container Options

When starting the Neo4j container, you can pass options in a variadic way to configure it.

Image

If you need to set a different Neo4j Docker image, you can use testcontainers.WithImage with a valid Docker image for Neo4j. E.g. testcontainers.WithImage("docker.io/neo4j:4.4").

By default, the container will use the following Docker image:

defaultImageName = "neo4j"
defaultTag       = "4.4"

Image Substitutions

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 operations: ImageSubstitutor, and a No-operation implementation to be used as reference for custom implementations:

// ImageSubstitutor represents a way to substitute container image names
type ImageSubstitutor interface {
    // Description returns the name of the type and a short description of how it modifies the image.
    // Useful to be printed in logs
    Description() string
    Substitute(image string) (string, error)
}

type NoopImageSubstitutor struct{}

// Description returns a description of what is expected from this Substitutor,
// which is used in logs.
func (s NoopImageSubstitutor) Description() string {
    return "NoopImageSubstitutor (noop)"
}

// Substitute returns the original image, without any change
func (s NoopImageSubstitutor) Substitute(image string) (string, error) {
    return image, nil
}

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.

WithEnv

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

postgres, err = postgresModule.RunContainer(ctx, testcontainers.WithEnv(map[string]string{"POSTGRES_INITDB_ARGS": "--no-sync"}))

WithHostPortAccess

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

postgres, err = postgresModule.RunContainer(ctx, testcontainers.WithHostPortAccess(8080))

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

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))
}

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 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 := TestLogger(t)
    _, err := postgresModule.RunContainer(ctx, testcontainers.WithLogger(logger))
    require.NoError(t, err)
    // Do something with container.
}

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

Wait Strategies

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.

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

Startup Commands

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.

Ready Commands

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.

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.

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.

Docker type modifiers

If you need an advanced configuration for the container, you can leverage the following Docker type modifiers:

  • testcontainers.WithConfigModifier
  • testcontainers.WithHostConfigModifier
  • testcontainers.WithEndpointSettingsModifier

Please read the Create containers: Advanced Settings documentation for more information.

Customising the ContainerRequest

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

container, err := RunContainer(ctx,
    /* 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.

Logger

This option sets a custom logger to be used by the container. Consider calling this before other With functions as these may generate logs.

Info

The logger must implement the testcontainers.Logger interface.

logger := &inMemoryLogger{}
container, err := neo4j.RunContainer(ctx,
    neo4j.WithLogger(logger), // needs to go before WithNeo4jSetting and WithNeo4jSettings
    neo4j.WithAdminPassword(testPassword),
    neo4j.WithNeo4jSetting("some.key", "value1"),
    neo4j.WithNeo4jSettings(map[string]string{"some.key": "value2"}),
    neo4j.WithNeo4jSetting("some.key", "value3"),
)

Authentication

By default, the Neo4j container will be started with authentication disabled. If you need to enable authentication, you can use the WithAuthentication(pwd string) option.

By default, the container will not use authentication, automatically prepending the WithoutAuthentication option to the options list.

Plugins

By default, the Neo4j container will start without any Labs plugins enabled, but you can enable them using the WithLabsPlugin optional function.

neo4j.WithLabsPlugin(neo4j.Apoc),

The list of available plugins is:

Apoc             LabsPlugin = "apoc"
ApocCore         LabsPlugin = "apoc-core"
Bloom            LabsPlugin = "bloom"
GraphDataScience LabsPlugin = "graph-data-science"
NeoSemantics     LabsPlugin = "n10s"
Streams          LabsPlugin = "streams"

Settings

It's possible to add Neo4j a single configuration setting to the container. The setting can be added as in the official Neo4j configuration, the function automatically translates the setting name (e.g. `dbms.tx_log.rotation.size) into the format required by the Neo4j container. This function can be called multiple times. A warning is emitted if a key is overwritten.

To pass multiple settings at once, the WithNeo4jSettings function is provided.

logger := &inMemoryLogger{}
container, err := neo4j.RunContainer(ctx,
    neo4j.WithLogger(logger), // needs to go before WithNeo4jSetting and WithNeo4jSettings
    neo4j.WithAdminPassword(testPassword),
    neo4j.WithNeo4jSetting("some.key", "value1"),
    neo4j.WithNeo4jSettings(map[string]string{"some.key": "value2"}),
    neo4j.WithNeo4jSetting("some.key", "value3"),
)

Warning

Credentials must be configured with the WithAdminPassword optional function.

Container Methods

Bolt URL

The BoltURL method returns the connection string to connect to the Neo4j container instance using the Bolt port. It returns a string with the format neo4j://<host>:<port>.

boltUrl, err := container.BoltUrl(ctx)