code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed 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 io.reactivex.rxjava3.internal.operators.maybe;
  
  import org.junit.Test;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.TestException;
  import io.reactivex.rxjava3.functions.Function;
  import io.reactivex.rxjava3.testsupport.TestHelper;
  
  public class MaybeFlattenTest extends RxJavaTest {
  
      @Test
      public void dispose() {
          TestHelper.checkDisposed(Maybe.just(1).flatMap(new Function<Integer, MaybeSource<Integer>>() {
              @Override
              public MaybeSource<Integer> apply(Integer v) throws Exception {
                  return Maybe.just(2);
              }
          }));
      }
  
      @Test
      public void doubleOnSubscribe() {
          TestHelper.checkDoubleOnSubscribeMaybe(new Function<Maybe<Integer>, MaybeSource<Integer>>() {
              @Override
              public MaybeSource<Integer> apply(Maybe<Integer> v) throws Exception {
                  return v.flatMap(new Function<Integer, MaybeSource<Integer>>() {
                      @Override
                      public MaybeSource<Integer> apply(Integer v) throws Exception {
                          return Maybe.just(2);
                      }
                  });
              }
          });
      }
  
      @Test
      public void mainError() {
          Maybe.<Integer>error(new TestException())
          .flatMap(new Function<Integer, MaybeSource<Integer>>() {
                      @Override
                      public MaybeSource<Integer> apply(Integer v) throws Exception {
                          return Maybe.just(2);
                      }
                  })
          .test()
          .assertFailure(TestException.class);
      }
  
      @Test
      public void mainEmpty() {
          Maybe.<Integer>empty()
          .flatMap(new Function<Integer, MaybeSource<Integer>>() {
                      @Override
                      public MaybeSource<Integer> apply(Integer v) throws Exception {
                          return Maybe.just(2);
                      }
                  })
          .test()
          .assertResult();
      }
  
      @Test
      public void mapperThrows() {
          Maybe.just(1)
          .flatMap(new Function<Integer, MaybeSource<Integer>>() {
                      @Override
                      public MaybeSource<Integer> apply(Integer v) throws Exception {
                          throw new TestException();
                      }
                  })
          .test()
          .assertFailure(TestException.class);
      }
  
      @Test
      public void mapperReturnsNull() {
          Maybe.just(1)
          .flatMap(new Function<Integer, MaybeSource<Integer>>() {
                      @Override
                      public MaybeSource<Integer> apply(Integer v) throws Exception {
                          return null;
                      }
                  })
          .test()
          .assertFailure(NullPointerException.class);
      }
  }
  