Logging errors with extended events excluding some users
Since you are using sql 2008R2, you cannot use like predicate comparisons as they were introduced with SQL Sever 2012.

If you are on SQL 2012, then you can use below query to find what is available :

select xp.name, xo.name, xo.description, xo.type_name, xo.type_size from
sys.dm_xe_objects xo
inner join sys.dm_xe_packages xp on xo.package_guid=xp.guid
where object_type like 'pred_compare'


SQL 2008 R2 does not have like_i_sql_unicode_string vs SQL 2012 has it.



So, below should work on SQL 2012

CREATE EVENT SESSION [ErrorCapture] 
ON SERVER 
ADD EVENT sqlserver.error_reported
(
    ACTION
    (
        sqlserver.client_hostname,
        sqlserver.database_id,
        sqlserver.sql_text,
        sqlserver.username
    )
    WHERE (
            [severity] &gt;= (11) AND
            (NOT sqlserver.like_i_sql_unicode_string(sqlserver.username,N'test%'))

    )

) 
ADD TARGET package0.asynchronous_file_target
(
    SET filename='C:\ErrorCapture_Extended_Event.xel'
)
WITH 
(
    MAX_MEMORY=4096 KB,
    EVENT_RETENTION_MODE=ALLOW_SINGLE_EVENT_LOSS,
    MAX_DISPATCH_LATENCY=10 SECONDS,
    MAX_EVENT_SIZE=0 KB,
    MEMORY_PARTITION_MODE=NONE,
    TRACK_CAUSALITY=OFF,
    STARTUP_STATE=ON
);


Refer: Connect item Extended events predicate - NOT LIKE required