Integration testing with the Kubernetes Java Client

KubernetesTest.java

// Start a Kubernetes Cluster.  For building a controller we don't really
// need to have worker nodes. The control plane should be plenty.
// k3s server gives much more than that the controller-runtime test suite
// provides (no controller-manager and scheduler)
Path tempDir = Files.createTempDirectory("kube-cluster");
File kubeConfig = new File(tempDir.toFile(), "k3s.yaml");

Process k3sServer = new ProcessBuilder("k3s", "server", "--disable-agent",
  "--bind-address", "127.0.0.1",
  "--data-dir", tempDir.toString(),
  "--write-kubeconfig", kubeConfig.toString())
  .start();

// k3s server generates a KUBECONFIG file for the admin account.  Wait until
// this file is available
while (true) {
  if (kubeConfig.exists()) break;
  Thread.sleep(500);
}

KubeConfig config = KubeConfig.loadKubeConfig(new FileReader(kubeConfig));
ApiClient admin = ClientBuilder.kubeconfig(config)
  .build();
admin.setDebugging(true);

// Wait until the apiserver is actually ready.
while (true) {
  int code = admin.buildCall("/readyz", "GET",
    null, null, null, Map.of(), Map.of(), null,
    new String[]{"BearerToken"}, null)
    .execute().code();
  if (code == 200) break;
  Thread.sleep(500);
}

CoreV1Api core = new CoreV1Api(admin);
V1NamespaceList namespaces = core.listNamespace(null, null, null, null, null,
  null, null, null, null, null);
System.out.println(namespaces);

// Wait for the k3s server to finish
k3sServer.destroy();
FileUtils.deleteDirectory(tempDir.toFile());