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.support.ui;
  
  import static org.assertj.core.api.Assertions.assertThat;
  import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
  
  import org.junit.jupiter.api.Tag;
  import org.junit.jupiter.api.Test;
  
  @Tag("UnitTests")
  class LoadableComponentTest {
    @Test
    void testShouldDoNothingIfComponentIsAlreadyLoaded() {
      new DetonatingComponent().get();
    }
  
    @Test
    void testShouldCauseTheLoadMethodToBeCalledIfTheComponentIsNotAlreadyLoaded() {
      LoadsOk ok = new LoadsOk(true);
  
      ok.get();
  
      assertThat(ok.wasLoadCalled()).isTrue();
    }
  
    @Test
    void testShouldThrowAnErrorIfCallingLoadDoesNotCauseTheComponentToLoad() {
      LoadsOk ok = new LoadsOk(false);
  
      assertThatExceptionOfType(Error.class).isThrownBy(ok::get).withMessage("Expected failure");
    }
  
    private static class DetonatingComponent extends LoadableComponent<DetonatingComponent> {
  
      @Override
      protected void load() {
        throw new RuntimeException("I should never be called");
      }
  
      @Override
      protected void isLoaded() throws Error {
        // Do nothing
      }
    }
  
    private static class LoadsOk extends LoadableComponent<LoadsOk> {
      private final boolean secondLoadCallPasses;
      private boolean callOfLoadMethodForced;
      private boolean loadCalled;
  
      public LoadsOk(boolean secondLoadCallPasses) {
        this.secondLoadCallPasses = secondLoadCallPasses;
      }
  
      @Override
      protected void load() {
        loadCalled = true;
      }
  
      @Override
      protected void isLoaded() throws Error {
        if (!callOfLoadMethodForced) {
          callOfLoadMethodForced = true;
          throw new Error("Never reported in test");
        }
  
        if (!secondLoadCallPasses) {
          throw new Error("Expected failure");
        }
      }
  
      public boolean wasLoadCalled() {
        return loadCalled;
      }
    }
  }
  