@Test
public void testDockerContainerMounts() throws IOException {

  launcher.yarnDockerMode = true;
  launcher.envVars.put(AbstractLauncher.ENV_DOCKER_CONTAINER_MOUNTS,
      "s1:t1:ro");
  launcher.mountPaths.put("s2", "t2");
  launcher.completeContainerLaunch();
  String dockerContainerMounts = launcher.containerLaunchContext
      .getEnvironment().get(AbstractLauncher.ENV_DOCKER_CONTAINER_MOUNTS);
  Assert.assertEquals("s1:t1:ro,s2:t2:ro", dockerContainerMounts);
}