How can I test the following method in the main method:

public static boolean hasMutation(String sequence) {

for ( int i = 0 ; i < sequence.length() ; i++ ) {

for ( int j = i + 1 ; j < sequence.length() ; j++ ) {

if ( sequence.charAt(i) == sequence.charAt(j) ) {

return true;

}

}

}

return false;

}