Testcontainers

Testcontainers is a NodeJS library that supports tests, providing lightweight, throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container.

Install

npm i -D testcontainers

Usage

Run your app with the DEBUG=testcontainers environment variable set to see debug output.

The following environment variables are supported:

Key	Example value	Behaviour
DOCKER_HOST	tcp://docker:2375	Override the Docker host, useful for DIND in CI environments

Common Issues

1. Insufficient Docker memory

By default, Docker sets CPU and memory limits, with a default memory limit of 2GB. If exceeded, you will be unable to pull/run Docker images. To see how much memory Docker has used, you can run docker system info

• To remove existing containers and images to clear some space you can run docker system prune
• Alternatively you can increase the memory limit via Docker's settings under the Advanced pane.

2. Insufficient test timeouts

It can take a few seconds up to a few minutes to pull and run certain Docker images, depending on file sizes and network constraints. It's unlikely that the default timeouts set by test frameworks are sufficient.

• Increase the test timeout via the methods provided by the testing framework.

Examples

Using a pre-built Docker image:

const redis = require("async-redis");
const { GenericContainer } = require("testcontainers");

(async () => {
  const container = await new GenericContainer("redis")
    .withExposedPorts(6379)
    .start();
  
  const redisClient = redis.createClient(
    container.getMappedPort(6379),
    container.getContainerIpAddress(),
  );
  await redisClient.quit();

  await container.stop();
})();

Using a specific image version:

const { GenericContainer } = require("testcontainers");

const container = await new GenericContainer("alpine", "3.10")
  .start();

Building and using your own Docker image:

const path = require("path");
const { GenericContainer } = require("testcontainers");

const buildContext = path.resolve(__dirname, "dir-containing-dockerfile");

const container = await GenericContainer.fromDockerfile(buildContext)
  .withBuildArg("ARG_KEY", "ARG_VALUE")
  .build();

const startedContainer = await container
  .withExposedPorts(8080)
  .start();

Creating a container with a specified name:

const { GenericContainer } = require("testcontainers");

const container = await new GenericContainer("alpine")
  .withName("custom-container-name")
  .start();

Creating a container with a command:

const { GenericContainer } = require("testcontainers");

const container = await new GenericContainer("alpine")
  .withCmd(["top"])
  .start();

Execute commands inside a running container:

const { GenericContainer } = require("testcontainers");

const container = await new GenericContainer("alpine")
  .start();

const { output, exitCode } = await container.exec(["echo", "hello", "world"]);

Creating a container with bind mounts:

const { GenericContainer } = require("testcontainers");

const container = await new GenericContainer("alpine")
  .withBindMount("/local/file.txt", "/remote/file.txt")
  .withBindMount("/local/dir", "/remote/dir", "ro")
  .start();

Creating a container with a tmpfs mount:

const { GenericContainer } = require("testcontainers");

const container = await new GenericContainer("postgres")
  .withExposedPorts(5432)
  .withTmpFs({ "/temp_pgdata": "rw,noexec,nosuid,size=65536k" })
  .start();

Creating a container with environment variables:

const { GenericContainer } = require("testcontainers");

const container = await new GenericContainer("alpine")
  .withEnv("ENV_KEY", "ENV_VALUE")
  .start();

Testcontainers will wait 10 seconds for a container to stop, to override:

const { GenericContainer } = require("testcontainers");
const { Duration, TemporalUnit } = require("node-duration");

const container = await new GenericContainer("postgres")
  .withExposedPorts(5432)
  .start();

await container.stop({ 
  timeout: new Duration(10, TemporalUnit.SECONDS) 
})

Testcontainers will remove associated volumes created by the container when stopped, to override:

const { GenericContainer } = require("testcontainers");

const container = await new GenericContainer("postgres")
  .withExposedPorts(5432)
  .start();

await container.stop({ 
  removeVolumes: false
})

Wait Strategies

Ordinarily Testcontainers will wait for up to 60 seconds for the container's mapped network ports to start listening. If the default 60s timeout is not sufficient, it can be altered with the withStartupTimeout() method:

const { GenericContainer } = require("testcontainers");
const { Duration, TemporalUnit } = require("node-duration");

const container = await new GenericContainer("redis")
  .withExposedPorts(6379)
  .withStartupTimeout(new Duration(100, TemporalUnit.SECONDS))
  .start();

Log output Wait Strategy

In some situations a container's log output is a simple way to determine if it is ready or not. For example, we can wait for a Ready message in the container's logs as follows:

const { GenericContainer, Wait } = require("testcontainers");

const container = await new GenericContainer("redis")
  .withExposedPorts(6379)
  .withWaitStrategy(Wait.forLogMessage("Ready to accept connections"))
  .start();