The four men were arrested last week for their alleged involvement in the planning or execution of attacks in Barcelona on Thursday and the northeastern resort town of Cambrils early Friday.
They were to testify before National Court Judge Fernando Andreu in Madrid. The judge will decide whether they should be jailed preventively or released, with or without conditions.
The four were arrested following the attacks: Three in the northern Catalan town of Ripoll and another in Alcanar, south of Barcelona, where a house that was accidentally blown apart turned out to be a botched bomb-making workshop.
The lone fugitive from the cell was shot to death Monday after he flashed what turned out to be a fake suicide belt at two troopers who confronted him in a vineyard not far from the city he terrorized.
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Abouyaaqoub's brother and friends made up the rest of the 12-man extremist cell, along with an imam who was one of two people killed in the Alcanar house.
Police said that with Abouyaaqoub's death, the group responsible for last week's fatal van attacks has now been broken.
Five of the 12 suspects were shot dead by police in the seaside town of Cambrils, where a second van attack left one pedestrian dead hours after the Barcelona van attack.