YOU MIGHT TRY ENCLOSING THE TESTERNAME PARAMETERS PARENS LIKE THIS:
And
(
TESTCYCL.TC_ACTUAL_TESTER = 'Testername'
OR TESTCYCL.TC_ACTUAL_TESTER = 'Testername'
OR TESTCYCL.TC_ACTUAL_TESTER = 'Testername'
OR TESTCYCL.TC_ACTUAL_TESTER = 'Testername'
OR TESTCYCL.TC_ACTUAL_TESTER = 'Testername'
OR TESTCYCL.TC_ACTUAL_TESTER = 'Testernamer'
OR TESTCYCL.TC_ACTUAL_TESTER = 'Testername'
)