Spring boot doesn't create DB from properties

Question

I add this properties to my spring boot application:

spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017
spring.data.mongodb.database=library

and write code:

    User user = new User();
    user.setFirstName("Name");
    user.setLastName("LastName");
    User newUser = userService.create(user);

But when I save user I have a new DB - test.users But I set DB name library in properties. Why spring creates DB with name test and doesn't create DB

library