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.grid.testing;
  
  import org.assertj.core.api.AbstractAssert;
  import org.openqa.selenium.internal.Either;
  
  public class EitherAssert<A, B> extends AbstractAssert<EitherAssert<A, B>, Either<A, B>> {
    public EitherAssert(Either<A, B> actual) {
      super(actual, EitherAssert.class);
    }
  
    public EitherAssert<A, B> isLeft() {
      isNotNull();
      if (actual.isRight()) {
        failWithMessage("Expected Either to be left but it is right: %s", actual.right());
      }
      return this;
    }
  
    public EitherAssert<A, B> isRight() {
      isNotNull();
      if (actual.isLeft()) {
        failWithMessage("Expected Either to be right but it is left: %s", actual.left());
      }
      return this;
    }
  }
  