How to create a container

Testcontainers are a wrapper around the Docker daemon designed for tests. Anything you can run in Docker, you can spin up with Testcontainers and integrate into your tests: * NoSQL databases or other data stores (e.g. Redis, ElasticSearch, MongoDB) * Web servers/proxies (e.g. NGINX, Apache) * Log services (e.g. Logstash, Kibana) * Other services developed by your team/organization which are already dockerized

GenericContainer

testcontainers.GenericContainer defines the container that should be run, similar to the docker run command.

The following test creates an NGINX container and validates that it returns 200 for the status code:

package main

import (
    "context"
    "fmt"
    "net/http"
    "testing"

    "github.com/testcontainers/testcontainers-go"
    "github.com/testcontainers/testcontainers-go/wait"
)

type nginxContainer struct {
    testcontainers.Container
    URI string
}


func setupNginx(ctx context.Context) (*nginxContainer, error) {
    req := testcontainers.ContainerRequest{
        Image:        "nginx",
        ExposedPorts: []string{"80/tcp"},
        WaitingFor:   wait.ForHTTP("/"),
    }
    container, err := testcontainers.GenericContainer(ctx, testcontainers.GenericContainerRequest{
        ContainerRequest: req,
        Started:          true,
    })
    if err != nil {
        return nil, err
    }

    ip, err := container.Host(ctx)
    if err != nil {
        return nil, err
    }

    mappedPort, err := container.MappedPort(ctx, "80")
    if err != nil {
        return nil, err
    }

    uri := fmt.Sprintf("http://%s:%s", ip, mappedPort.Port())

    return &nginxContainer{Container: container, URI: uri}, nil
}

func TestIntegrationNginxLatestReturn(t *testing.T) {
    if testing.Short() {
        t.Skip("skipping integration test")
    }

    ctx := context.Background()

    nginxC, err := setupNginx(ctx)
    if err != nil {
        t.Fatal(err)
    }

    // Clean up the container after the test is complete
    t.Cleanup(func() {
        if err := nginxC.Terminate(ctx); err != nil {
            t.Fatalf("failed to terminate container: %s", err)
        }
    })

    resp, err := http.Get(nginxC.URI)
    if resp.StatusCode != http.StatusOK {
        t.Fatalf("Expected status code %d. Got %d.", http.StatusOK, resp.StatusCode)
    }
}

Advanced Settings

The aforementioned GenericContainer function and the ContainerRequest struct represent a straightforward manner to configure the containers, but you could need to create your containers with more advance settings regarding the config, host config and endpoint settings Docker types. For those more advance settings, Testcontainers for Go offers a way to fully customise the container request and those internal Docker types. These customisations, called modifiers, will be applied just before the internal call to the Docker client to create the container.

Using modifiers

req := ContainerRequest{
    Image: nginxAlpineImage, // alpine image does expose port 80
    ConfigModifier: func(config *container.Config) {
        config.Env = []string{"a=b"}
    },
    Mounts: ContainerMounts{
        {
            Source: DockerBindMountSource{
                HostPath: "/var/lib/app/data",
                BindOptions: &mount.BindOptions{
                    Propagation: mount.PropagationPrivate,
                },
            },
            Target: "/data",
        },
    },
    HostConfigModifier: func(hostConfig *container.HostConfig) {
        hostConfig.PortBindings = nat.PortMap{
            "80/tcp": []nat.PortBinding{
                {
                    HostIP:   "1",
                    HostPort: "2",
                },
            },
        }
    },
    EnpointSettingsModifier: func(endpointSettings map[string]*network.EndpointSettings) {
        endpointSettings["a"] = &network.EndpointSettings{
            Aliases: []string{"b"},
            Links:   []string{"link1", "link2"},
        }
    },
}

Warning

The only special case where the modifiers are not applied last, is when there are no exposed ports in the container request and the container does not use a network mode from a container (e.g. req.NetworkMode = container.NetworkMode("container:$CONTAINER_ID")). In that case, Testcontainers for Go will extract the ports from the underliying Docker image and export them.

Reusable container

With Reuse option you can reuse an existing container. Reusing will work only if you pass an existing container name via 'req.Name' field. If the name is not in a list of existing containers, the function will create a new generic container. If Reuse is true and Name is empty, you will get error.

The following test creates an NGINX container, adds a file into it and then reuses the container again for checking the file:

package main

import (
    "context"
    "fmt"
    "log"

    "github.com/testcontainers/testcontainers-go"
)

const (
    reusableContainerName = "my_test_reusable_container"
)

ctx := context.Background()

n1, err := GenericContainer(ctx, GenericContainerRequest{
    ContainerRequest: ContainerRequest{
        Image:        "nginx:1.17.6",
        ExposedPorts: []string{"80/tcp"},
        WaitingFor:   wait.ForListeningPort("80/tcp"),
        Name:         reusableContainerName,
    },
    Started: true,
})
if err != nil {
    log.Fatal(err)
}
defer n1.Terminate(ctx)

copiedFileName := "hello_copy.sh"
err = n1.CopyFileToContainer(ctx, "./testresources/hello.sh", "/"+copiedFileName, 700)

if err != nil {
    log.Fatal(err)
}

n2, err := GenericContainer(ctx, GenericContainerRequest{
    ContainerRequest: ContainerRequest{
        Image:        "nginx:1.17.6",
        ExposedPorts: []string{"80/tcp"},
        WaitingFor:   wait.ForListeningPort("80/tcp"),
        Name:         reusableContainerName,
    },
    Started: true,
    Reuse: true,
})
if err != nil {
    log.Fatal(err)
}

c, _, err := n2.Exec(ctx, []string{"bash", copiedFileName})
if err != nil {
    log.Fatal(err)
}
fmt.Println(c)

Parallel running

testcontainers.ParallelContainers - defines the containers that should be run in parallel mode.

The following test creates two NGINX containers in parallel:

package main

import (
    "context"
    "fmt"
    "log"

    "github.com/testcontainers/testcontainers-go"
)

func main() {
    ctx := context.Background()

    requests := testcontainers.ParallelContainerRequest{
        {
            ContainerRequest: testcontainers.ContainerRequest{

                Image: "nginx",
                ExposedPorts: []string{
                    "10080/tcp",
                },
            },
            Started: true,
        },
        {
            ContainerRequest: testcontainers.ContainerRequest{

                Image: "nginx",
                ExposedPorts: []string{
                    "10081/tcp",
                },
            },
            Started: true,
        },
    }

    res, err := testcontainers.ParallelContainers(ctx, requests, testcontainers.ParallelContainersOptions{})
    if err != nil {
        e, ok := err.(testcontainers.ParallelContainersError)
        if !ok {
            log.Fatalf("unknown error: %v", err)
        }

        for _, pe := range e.Errors {
            fmt.Println(pe.Request, pe.Error)
        }
        return
    }

    for _, c := range res {
        c := c
        defer func() {
            if err := c.Terminate(ctx); err != nil {
                log.Fatalf("failed to terminate container: %s", c)
            }
        }()
    }
}