create table logins  
( Personid varchar2(10)  
, Login_time date  
)

begin 
insert into logins (Personid, Login_time) values (1, to_date('01012021 00:00', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (1, to_date('01012021 01:00', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (1, to_date('01012021 01:59', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (1, to_date('01012021 02:00', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (1, to_date('01012021 02:39', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (1, to_date('01012021 03:00', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (1, to_date('01012021 04:59', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (2, to_date('01012021 01:01', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (2, to_date('01012021 01:30', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (2, to_date('01012021 02:00', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (2, to_date('01012021 05:00', 'DDMMYYYY HH24:MI')); 
insert into logins (Personid, Login_time) values (2, to_date('01012021 06:00', 'DDMMYYYY HH24:MI')); 
end;

create or replace view 
my_query 
as 
select personid  
,      to_char(login_time,'HH24:MI') block_start_login_time  
from logins  
match_recognize (  
  partition by personid -- regard every person independently  
  order by login_time  
  measures   
         match_number()     mn,  
         block_start.login_time    as login_time    
  one row per match -- every block is represented by a single record   
  pattern (block_start same_block*) -- collect a log in record and all subsequent rows in same two hour block; once a row is assigned to a block it cannot start or be part of another block    
  define  
       same_block as (login_time <= block_start.login_time + interval '2' hour)  -- a login row is in the same block with its subsequent rows within 2 hours  
)  

with result_to_verify as 
( select block_start_login_time  login_time 
  from   my_query 
  where  personid = 1 
) 
, expected_result as 
( select '00:00' from dual 
  union all 
  select '02:39' from dual 
  union all 
  select '04:59' from dual 
) 
(select *   
from result_to_verify   
minus   
select *   
from expected_result   
) -- superfluous results
union all   
( 
select *   
from expected_result   
minus   
select *   
from result_to_verify   
) -- missing results

with result_to_verify as 
( select block_start_login_time  login_time 
  from   my_query 
  where  personid = 1 
) 
, expected_result as 
( select '00:00' from dual 
  union all 
  select '02:39' from dual 
  union all 
  select '04:59' from dual 
) 
(select *   
from result_to_verify   
minus   
select *   
from expected_result   
) -- superfluous results
union all   
( 
select *   
from expected_result   
minus   
select *   
from result_to_verify   
) -- missing results

with result_to_verify as 
( select block_start_login_time  login_time 
  from   my_query 
  where  personid = 2 
) 
, expected_result as 
( select '01:01' from dual 
  union all 
  select '05:00' from dual 
) 
(select *   
from result_to_verify   
minus   
select *   
from expected_result   
) -- superfluous results
union all   
( 
select *   
from expected_result   
minus   
select *   
from result_to_verify   
) -- missing results

Define expected results as JSON document

with expected_result as (   
  SELECT *   
  FROM JSON_TABLE('   
  [ {"PERSONID" : "1", "BLOCK_START_LOGIN_TIME" : "00:00"}   
  , {"PERSONID" : "1", "BLOCK_START_LOGIN_TIME" : "02:39"}   
  , {"PERSONID" : "1", "BLOCK_START_LOGIN_TIME" : "04:59"}   
  ]' , '$[*]'   
  COLUMNS (PERSONID VARCHAR2(10) PATH '$.PERSONID',   
           BLOCK_START_LOGIN_TIME VARCHAR2 PATH '$.BLOCK_START_LOGIN_TIME'   
           )   
  )   
)   
, result_to_verify as (   
  select PERSONID  
  ,      BLOCK_START_LOGIN_TIME
  from   my_query   
)   
(select *   
from result_to_verify   
minus   
select *   
from expected_result   
) -- superfluous results
union all   
( 
select *   
from expected_result   
minus   
select *   
from result_to_verify   
) -- missing results

More compact JSON definition

with expected_result as (   
  SELECT *   
  FROM JSON_TABLE('   
  [ {"P" : "1", "B" : "00:00"}   
  , {"P" : "1", "B" : "02:39"}   
  , {"P" : "1", "B" : "04:59"}   
  ]' , '$[*]'   
  COLUMNS (PERSONID VARCHAR2(10) PATH '$.P',   
           BLOCK_START_LOGIN_TIME VARCHAR2 PATH '$.B'   
           )   
  )   
)   
, result_to_verify as (   
  select PERSONID  
  ,      BLOCK_START_LOGIN_TIME
  from   my_query   
)   
(select *   
from result_to_verify   
minus   
select *   
from expected_result   
) -- superfluous results
union all   
( 
select *   
from expected_result   
minus   
select *   
from result_to_verify   
) -- missing results

And even more compact and cryptic JSON document

with expected_result as (   
  SELECT *   
  FROM JSON_TABLE('[   
    ["1", "00:00"]   
  , ["1", "02:39"]
  , ["1", "04:59"]
  ]' , '$[*]'   
  COLUMNS (X VARCHAR2(10) PATH '$[0]',   
           Y VARCHAR2 PATH '$[1]'   
           )   
  )   
)   
, result_to_verify as (   
  select PERSONID  
  ,      BLOCK_START_LOGIN_TIME
  from   my_query   
)   
( select *   
  from result_to_verify   
  minus   
  select *   
  from expected_result   
) -- superfluous results
union all   
( 
  select *   
  from expected_result   
  minus   
  select *   
  from result_to_verify   
  ) -- missing results