assertThrows(
        NullPointerException.class,
        () -> builder.putAll(Collections.<String, Integer>singletonMap("one", null)));
  }

  @SuppressWarnings("AlwaysThrows")
  public void testPuttingTheSameKeyTwiceThrowsOnBuild() {
    Builder<String, Integer> builder =
        new Builder<String, Integer>()
            .put("one", 1)

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@link ImmutableMap}.
 *
 * @author Kevin Bourrillion
 * @author Jesse Wilson
 */
@GwtCompatible(emulated = true)
@SuppressWarnings("AlwaysThrows")
@ElementTypesAreNonnullByDefault
public class ImmutableMapTest extends TestCase {

  @J2ktIncompatible
  @GwtIncompatible // suite
  public static Test suite() {
    TestSuite suite = new TestSuite();

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@link ImmutableMap}.
 *
 * @author Kevin Bourrillion
 * @author Jesse Wilson
 */
@GwtCompatible(emulated = true)
@SuppressWarnings("AlwaysThrows")
@ElementTypesAreNonnullByDefault
public class ImmutableMapTest extends TestCase {

  @J2ktIncompatible
  @GwtIncompatible // suite
  public static Test suite() {
    TestSuite suite = new TestSuite();