builder.put("key", "value");
    assertThat(builder.build().entries()).containsExactly(Maps.immutableEntry("key", "value"));
  }

  public void testBuilder_withImmutableEntry() {
    ImmutableListMultimap<String, Integer> multimap =
        new Builder<String, Integer>().put(Maps.immutableEntry("one", 1)).build();
    assertEquals(Arrays.asList(1), multimap.get("one"));
  }

            .put("one", 1);
    assertMapEquals(builder.buildKeepingLast(), "one", 1);
    assertThrows(IllegalArgumentException.class, () -> builder.buildOrThrow());
  }

  public void testBuilder_withImmutableEntry() {
    ImmutableMap<String, Integer> map =
        new Builder<String, Integer>().put(immutableEntry("one", 1)).buildOrThrow();
    assertMapEquals(map, "one", 1);
  }