code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC licenses this file
  // to you under the Apache License, Version 2.0 (the
  // "License"); you may not use this file except in compliance
  // with the License.  You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing,
  // software distributed under the License is distributed on an
  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied.  See the License for the
  // specific language governing permissions and limitations
  // under the License.
  
  package org.openqa.selenium.docker;
  
  import static java.net.HttpURLConnection.HTTP_INTERNAL_ERROR;
  import static org.assertj.core.api.Assertions.assertThat;
  import static org.openqa.selenium.remote.http.Contents.utf8String;
  
  import java.io.IOException;
  import java.io.UncheckedIOException;
  import java.util.Optional;
  import org.junit.jupiter.api.Test;
  import org.openqa.selenium.remote.http.HttpHandler;
  import org.openqa.selenium.remote.http.HttpResponse;
  
  // https://docs.docker.com/engine/api/v1.41/#operation/SystemVersion
  class VersionCommandTest {
  
    @Test
    void ifDockerIsDownReturnEmpty() {
      HttpHandler handler =
          req -> {
            throw new UncheckedIOException(new IOException("Eep"));
          };
  
      Optional<DockerProtocol> maybeDocker = new VersionCommand(handler).getDockerProtocol();
  
      assertThat(maybeDocker).isNotPresent();
    }
  
    @Test
    void shouldReturnEmptyIfServerReturnsAnUnsuccessfulResponseStatus() {
      HttpHandler handler = req -> new HttpResponse().setStatus(HTTP_INTERNAL_ERROR);
  
      Optional<DockerProtocol> maybeDocker = new VersionCommand(handler).getDockerProtocol();
  
      assertThat(maybeDocker).isNotPresent();
    }
  
    @Test
    void shouldReturnEmptyIfServerDoesNotSupportOurVersionOfTheDockerApi() {
      // We only support v1.40+
      HttpHandler handler =
          req ->
              new HttpResponse()
                  .addHeader("Content-Type", "application/json")
                  .setContent(utf8String("{\"ApiVersion\":\"1.12\",\"MinAPIVersion\":\"1.2\"}"));
  
      Optional<DockerProtocol> maybeDocker = new VersionCommand(handler).getDockerProtocol();
  
      assertThat(maybeDocker).isNotPresent();
    }
  
    @Test
    void shouldReturnEmptyIfServerVersionOfDockerApiIsHigherThanAnyWeSupport() {
      // I sincerely hope that there is no version "9999999" of the docker protocol.
      HttpHandler handler =
          req ->
              new HttpResponse()
                  .addHeader("Content-Type", "application/json")
                  .setContent(
                      utf8String("{\"ApiVersion\":\"9999999.12\",\"MinAPIVersion\":\"9999999.0\"}"));
  
      Optional<DockerProtocol> maybeDocker = new VersionCommand(handler).getDockerProtocol();
  
      assertThat(maybeDocker).isNotPresent();
    }
  
    @Test
    void shouldReturnADockerInstanceIfTheVersionOfTheApiSupportedIsOneSeleniumAlsoSupports() {
      HttpHandler handler =
          req ->
              new HttpResponse()
                  .addHeader("Content-Type", "application/json")
                  // Note: the version here does not exactly match any we claim to provide
                  .setContent(utf8String("{\"ApiVersion\":\"1.42\",\"MinAPIVersion\":\"1.12\"}"));
  
      Optional<DockerProtocol> maybeDocker = new VersionCommand(handler).getDockerProtocol();
  
      assertThat(maybeDocker).isPresent();
      assertThat(maybeDocker.get().version()).isEqualTo("1.41");
    }
  }
  