How to use Is class of org.hamcrest.core package

<dependency>
   <groupId>junit</groupId>
   <artifactId>junit</artifactId>
   <version>4.12</version>
   <scope>test</scope>
</dependency>
<dependency>
   <groupId>org.hamcrest</groupId>
   <artifactId>hamcrest-core</artifactId>
   <version>1.3</version>
   <scope>test</scope>
</dependency>
<dependency>
   <groupId>org.hamcrest</groupId>
   <artifactId>hamcrest-library</artifactId>
   <version>1.3</version>
   <scope>test</scope>
</dependency>

@Path("/authentication")
public class AuthenticationEndpoint {

    @POST
    @Produces(MediaType.APPLICATION_JSON)
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    public Response authenticateUser(@FormParam("username") String username, 
                                     @FormParam("password") String password) {

        try {

            // Authenticate the user using the credentials provided
            authenticate(username, password);

            // Issue a token for the user
            String token = issueToken(username);

            // Return the token on the response
            return Response.ok(token).build();

        } catch (Exception e) {
            return Response.status(Response.Status.FORBIDDEN).build();
        }      
    }

    private void authenticate(String username, String password) throws Exception {
        // Authenticate against a database, LDAP, file or whatever
        // Throw an Exception if the credentials are invalid
    }

    private String issueToken(String username) {
        // Issue a token (can be a random String persisted to a database or a JWT token)
        // The issued token must be associated to a user
        // Return the issued token
    }
}

public enum Role {
    ROLE_1,
    ROLE_2,
    ROLE_3
}

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