// Path: cfg4j-core/src/main/java/org/cfg4j/source/ConfigurationSource.java
// public interface ConfigurationSource {
// 
//   /**
//    * Get configuration set for a given {@code environment} from this source in a form of {@link Properties}.
//    * Provided {@link Environment} will be used to determine which environment to use.
//    *
//    * @param environment environment to use
//    * @return configuration set for {@code environment}
//    * @throws MissingEnvironmentException when requested environment couldn't be found
//    * @throws IllegalStateException       when unable to fetch configuration
//    */
//   Properties getConfiguration(Environment environment);
// 
//   /**
//    * Initialize this source. This method has to be called before any other method of this instance.
//    *
//    * @throws IllegalStateException        when source was improperly configured
//    * @throws SourceCommunicationException when unable to communicate with source
//    */
//   void init();
// }
// 
// Path: cfg4j-core/src/main/java/org/cfg4j/source/SourceCommunicationException.java
// public class SourceCommunicationException extends RuntimeException {
// 
//   /**
//    * Indicates problem when communicating with {@link ConfigurationSource}.
//    *
//    * @param msg the detail message
//    * @param e   the cause
//    */
//   public SourceCommunicationException(String msg, Exception e) {
//     super("Unable to communicate with configuration source: " + msg, e);
//   }
// }
// 
// Path: cfg4j-core/src/main/java/org/cfg4j/source/context/environment/Environment.java
// public interface Environment {
// 
//   /**
//    * Name of the environment. Should not be null.
//    *
//    * @return environment name. Not null.
//    */
//   String getName();
// 
// }
// 
// Path: cfg4j-core/src/main/java/org/cfg4j/source/context/environment/MissingEnvironmentException.java
// public class MissingEnvironmentException extends RuntimeException {
// 
//   private static final String MISSING_ENV_MSG = "Missing environment: ";
// 
//   /**
//    * Environment named {@code envName} is missing.
//    *
//    * @param envName environment name
//    */
//   public MissingEnvironmentException(String envName) {
//     super(MISSING_ENV_MSG + envName);
//   }
// 
//   /**
//    * Environment named {@code envName} is missing.
//    *
//    * @param envName environment name
//    * @param cause root cause
//    */
//   public MissingEnvironmentException(String envName, Throwable cause) {
//     super(MISSING_ENV_MSG + envName, cause);
//   }
// }


import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import java.util.Properties;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.atLeastOnce;
import static org.mockito.Mockito.doNothing;
import static org.mockito.Mockito.doThrow;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
import org.assertj.core.data.MapEntry;
import org.cfg4j.source.ConfigurationSource;
import org.cfg4j.source.SourceCommunicationException;
import org.cfg4j.source.context.environment.Environment;
import org.cfg4j.source.context.environment.MissingEnvironmentException;
    when(underlyingSources[LAST_SOURCE_INDEX].getConfiguration(any(Environment.class))).thenReturn(getProps("prop1", "value1")[0]);

    assertThat(fallbackConfigurationSource.getConfiguration(mock(Environment.class)))
        .containsOnly(MapEntry.entry("prop1", "value1"));
  }

  @Test
  void initInitializesAllSources() {
    for (ConfigurationSource underlyingSource : underlyingSources) {
      verify(underlyingSource, atLeastOnce()).init();
    }
  }

  @Test
  void initThrowsWhenAllSourcesThrow() {
    makeAllSourcesThrow(new IllegalStateException());

    assertThatThrownBy(() -> fallbackConfigurationSource.init()).isExactlyInstanceOf(IllegalStateException.class);
  }

  @Test
  void initIgnoresIllegalStateExceptionsIfAtLeastOneSourceSucceeds() {
    makeAllSourcesThrow(new IllegalStateException());
    doNothing().when(underlyingSources[LAST_SOURCE_INDEX]).init();

    fallbackConfigurationSource.init();
  }

  @Test
  void initIgnoresSourceCommunicationExceptionsIfAtLeastOneSourceSucceeds() {
// Path: cfg4j-core/src/main/java/org/cfg4j/source/ConfigurationSource.java
// public interface ConfigurationSource {
// 
//   /**
//    * Get configuration set for a given {@code environment} from this source in a form of {@link Properties}.
//    * Provided {@link Environment} will be used to determine which environment to use.
//    *
//    * @param environment environment to use
//    * @return configuration set for {@code environment}
//    * @throws MissingEnvironmentException when requested environment couldn't be found
//    * @throws IllegalStateException       when unable to fetch configuration
//    */
//   Properties getConfiguration(Environment environment);
// 
//   /**
//    * Initialize this source. This method has to be called before any other method of this instance.
//    *
//    * @throws IllegalStateException        when source was improperly configured
//    * @throws SourceCommunicationException when unable to communicate with source
//    */
//   void init();
// }
// 
// Path: cfg4j-core/src/main/java/org/cfg4j/source/SourceCommunicationException.java
// public class SourceCommunicationException extends RuntimeException {
// 
//   /**
//    * Indicates problem when communicating with {@link ConfigurationSource}.
//    *
//    * @param msg the detail message
//    * @param e   the cause
//    */
//   public SourceCommunicationException(String msg, Exception e) {
//     super("Unable to communicate with configuration source: " + msg, e);
//   }
// }
// 
// Path: cfg4j-core/src/main/java/org/cfg4j/source/context/environment/Environment.java
// public interface Environment {
// 
//   /**
//    * Name of the environment. Should not be null.
//    *
//    * @return environment name. Not null.
//    */
//   String getName();
// 
// }
// 
// Path: cfg4j-core/src/main/java/org/cfg4j/source/context/environment/MissingEnvironmentException.java
// public class MissingEnvironmentException extends RuntimeException {
// 
//   private static final String MISSING_ENV_MSG = "Missing environment: ";
// 
//   /**
//    * Environment named {@code envName} is missing.
//    *
//    * @param envName environment name
//    */
//   public MissingEnvironmentException(String envName) {
//     super(MISSING_ENV_MSG + envName);
//   }
// 
//   /**
//    * Environment named {@code envName} is missing.
//    *
//    * @param envName environment name
//    * @param cause root cause
//    */
//   public MissingEnvironmentException(String envName, Throwable cause) {
//     super(MISSING_ENV_MSG + envName, cause);
//   }
// }


// Path: cfg4j-core/src/test/java/org/cfg4j/source/compose/FallbackConfigurationSourceTest.java
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import java.util.Properties;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.atLeastOnce;
import static org.mockito.Mockito.doNothing;
import static org.mockito.Mockito.doThrow;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
import org.assertj.core.data.MapEntry;
import org.cfg4j.source.ConfigurationSource;
import org.cfg4j.source.SourceCommunicationException;
import org.cfg4j.source.context.environment.Environment;
import org.cfg4j.source.context.environment.MissingEnvironmentException;

    when(underlyingSources[LAST_SOURCE_INDEX].getConfiguration(any(Environment.class))).thenReturn(getProps("prop1", "value1")[0]);

    assertThat(fallbackConfigurationSource.getConfiguration(mock(Environment.class)))
        .containsOnly(MapEntry.entry("prop1", "value1"));
  }

  @Test
  void initInitializesAllSources() {
    for (ConfigurationSource underlyingSource : underlyingSources) {
      verify(underlyingSource, atLeastOnce()).init();
    }
  }

  @Test
  void initThrowsWhenAllSourcesThrow() {
    makeAllSourcesThrow(new IllegalStateException());

    assertThatThrownBy(() -> fallbackConfigurationSource.init()).isExactlyInstanceOf(IllegalStateException.class);
  }

  @Test
  void initIgnoresIllegalStateExceptionsIfAtLeastOneSourceSucceeds() {
    makeAllSourcesThrow(new IllegalStateException());
    doNothing().when(underlyingSources[LAST_SOURCE_INDEX]).init();

    fallbackConfigurationSource.init();
  }

  @Test
  void initIgnoresSourceCommunicationExceptionsIfAtLeastOneSourceSucceeds() {
    makeAllSourcesThrow(new SourceCommunicationException("", null));