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.single;
  
  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 SingleConcatMapTest extends RxJavaTest {
  
      @Test
      public void concatMapValue() {
          Single.just(1).concatMap(new Function<Integer, SingleSource<Integer>>() {
              @Override public SingleSource<Integer> apply(final Integer integer) throws Exception {
                  if (integer == 1) {
                      return Single.just(2);
                  }
  
                  return Single.just(1);
              }
          })
              .test()
              .assertResult(2);
      }
  
      @Test
      public void concatMapValueDifferentType() {
          Single.just(1).concatMap(new Function<Integer, SingleSource<String>>() {
              @Override public SingleSource<String> apply(final Integer integer) throws Exception {
                  if (integer == 1) {
                      return Single.just("2");
                  }
  
                  return Single.just("1");
              }
          })
              .test()
              .assertResult("2");
      }
  
      @Test
      public void concatMapValueNull() {
          Single.just(1).concatMap(new Function<Integer, SingleSource<Integer>>() {
              @Override public SingleSource<Integer> apply(final Integer integer) throws Exception {
                  return null;
              }
          })
          .to(TestHelper.<Integer>testConsumer())
              .assertNoValues()
              .assertError(NullPointerException.class)
              .assertErrorMessage("The single returned by the mapper is null");
      }
  
      @Test
      public void concatMapValueErrorThrown() {
          Single.just(1).concatMap(new Function<Integer, SingleSource<Integer>>() {
              @Override public SingleSource<Integer> apply(final Integer integer) throws Exception {
                  throw new RuntimeException("something went terribly wrong!");
              }
          })
              .to(TestHelper.<Integer>testConsumer())
              .assertNoValues()
              .assertError(RuntimeException.class)
              .assertErrorMessage("something went terribly wrong!");
      }
  
      @Test
      public void concatMapError() {
          RuntimeException exception = new RuntimeException("test");
  
          Single.error(exception).concatMap(new Function<Object, SingleSource<Object>>() {
              @Override public SingleSource<Object> apply(final Object integer) throws Exception {
                  return Single.just(new Object());
              }
          })
              .test()
              .assertError(exception);
      }
  
      @Test
      public void dispose() {
          TestHelper.checkDisposed(Single.just(1).concatMap(new Function<Integer, SingleSource<Integer>>() {
              @Override
              public SingleSource<Integer> apply(Integer v) throws Exception {
                  return Single.just(2);
              }
          }));
      }
  
      @Test
      public void mappedSingleOnError() {
          Single.just(1).concatMap(new Function<Integer, SingleSource<Integer>>() {
              @Override
              public SingleSource<Integer> apply(Integer v) throws Exception {
                  return Single.error(new TestException());
              }
          })
          .test()
          .assertFailure(TestException.class);
      }
  
      @Test
      public void doubleOnSubscribe() {
          TestHelper.checkDoubleOnSubscribeSingle(new Function<Single<Object>, SingleSource<Object>>() {
              @Override
              public SingleSource<Object> apply(Single<Object> s)
                      throws Exception {
                  return s.concatMap(new Function<Object, SingleSource<? extends Object>>() {
                      @Override
                      public SingleSource<? extends Object> apply(Object v)
                              throws Exception {
                          return Single.just(v);
                      }
                  });
              }
          });
      }
  }
  