content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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.apache.beam.sdk.transforms;
  
  import static org.hamcrest.MatcherAssert.assertThat;
  import static org.hamcrest.Matchers.equalTo;
  
  import org.apache.beam.sdk.values.TypeDescriptors;
  import org.junit.Rule;
  import org.junit.Test;
  import org.junit.rules.ExpectedException;
  import org.junit.runner.RunWith;
  import org.junit.runners.JUnit4;
  
  /** Tests for {@link SimpleFunction}. */
  @RunWith(JUnit4.class)
  public class SimpleFunctionTest {
  
    @Rule public ExpectedException thrown = ExpectedException.none();
  
    @Test
    public void testFailureIfNotOverridden() {
      thrown.expect(IllegalStateException.class);
      thrown.expectMessage("must override");
      thrown.expectMessage("apply");
  
      new SimpleFunction<Integer, Integer>() {};
    }
  
    /**
     * Basic test of {@link MapElements} with a lambda (which is instantiated as a {@link
     * SerializableFunction}).
     */
    @Test
    public void testGoodTypeForLambda() throws Exception {
      SimpleFunction<Integer, String> fn = new SimpleFunction<Integer, String>(Object::toString) {};
  
      assertThat(fn.getInputTypeDescriptor(), equalTo(TypeDescriptors.integers()));
      assertThat(fn.getOutputTypeDescriptor(), equalTo(TypeDescriptors.strings()));
    }
  
    /**
     * Basic test of {@link MapElements} with a lambda wrapped into a {@link SimpleFunction} to
     * remember its type.
     */
    @Test
    public void testGoodTypeForMethodRef() throws Exception {
      SimpleFunction<Integer, String> fn =
          new SimpleFunction<Integer, String>(SimpleFunctionTest::toStringThisThing) {};
  
      assertThat(fn.getInputTypeDescriptor(), equalTo(TypeDescriptors.integers()));
      assertThat(fn.getOutputTypeDescriptor(), equalTo(TypeDescriptors.strings()));
    }
  
    private static String toStringThisThing(Integer i) {
      return i.toString();
    }
  }
  