### Question:
JcrUserProvider extends BaseJcrProvider<Object, Serializable> implements UserProvider { @Override public boolean userExists(@Nonnull String username) { return findUserBySystemName(username).isPresent(); }  @Nonnull @Override User ensureUser(@Nonnull final String systemName); @Nonnull @Override Optional<User> findUserBySystemName(@Nonnull final String systemName); @Override Class<? extends User> getEntityClass(); @Override Class<? extends JcrEntity<?>> getJcrEntityClass(); @Override String getNodeType(@Nonnull final Class<? extends JcrObject> jcrEntityType); @Override User.ID resolveId(@Nonnull final Serializable fid); @Override User.ID resolveUserId(@Nonnull Serializable id); @Override UserGroup.ID resolveGroupId(@Nonnull Serializable id); @Override boolean userExists(@Nonnull String username); @Nonnull @Override Optional<User> findUserById(@Nonnull User.ID id); @Nonnull @Override Iterable<User> findUsers(); @Nonnull @Override User createUser(@Nonnull String username); @Nonnull @Override Optional<UserGroup> findGroupById(ID id); @Nonnull @Override Optional<UserGroup> findGroupByName(@Nonnull final String groupName); @Nonnull @Override Iterable<UserGroup> findGroups(); @Nonnull @Override UserGroup ensureGroup(@Nonnull String groupName); @Nonnull @Override UserGroup createGroup(@Nonnull String groupName); @Override void deleteGroup(@Nonnull final UserGroup group); @Override void deleteUser(@Nonnull final User user); @Nonnull @Override UserGroup updateGroup(@Nonnull final UserGroup group); @Nonnull @Override User updateUser(@Nonnull final User user);  }### Answer:
@Test(dependsOnMethods = "testCreateUsers") public void testUserExists() { metadata.read(() -> { assertThat(this.provider.userExists("user1")).isTrue(); assertThat(this.provider.userExists("bogus")).isFalse(); }, MetadataAccess.SERVICE); }