I could retest you could retest he could retest we could retest you could retest they could retest
V-ing form
I could be retesting you could be retesting he could be retesting we could be retesting you could be retesting they could be retesting
Perfect
I could have retested you could have retested he could have retested we could have retested you could have retested they could have retested
V-ing perfect
I could have been retesting you could have been retesting he could have been retesting we could have been retesting you could have been retesting they could have been retesting
Negation
Simple form
I could not retest you could not retest he could not retest we could not retest you could not retest they could not retest
V-ing form
I could not be retesting you could not be retesting he could not be retesting we could not be retesting you could not be retesting they could not be retesting
Perfect
I could not have retested you could not have retested he could not have retested we could not have retested you could not have retested they could not have retested
V-ing perfect
I could not have been retesting you could not have been retesting he could not have been retesting we could not have been retesting you could not have been retesting they could not have been retesting
Interrogative form
Simple form
could I retest? could you retest? could he retest? could we retest? could you retest? could they retest?
V-ing form
could I be retesting? could you be retesting? could he be retesting? could we be retesting? could you be retesting? could they be retesting?
Perfect
could I have retested? could you have retested? could he have retested? could we have retested? could you have retested? could they have retested?
V-ing perfect
could I have been retesting? could you have been retesting? could he have been retesting? could we have been retesting? could you have been retesting? could they have been retesting?
Interro-negative form
Simple form
could I not retest? could you not retest? could he not retest? could we not retest? could you not retest? could they not retest?
V-ing form
could I not be retesting? could you not be retesting? could he not be retesting? could we not be retesting? could you not be retesting? could they not be retesting?
Perfect
could I not have retested? could you not have retested? could he not have retested? could we not have retested? could you not have retested? could they not have retested?
V-ing perfect
could I not have been retesting? could you not have been retesting? could he not have been retesting? could we not have been retesting? could you not have been retesting? could they not have been retesting?