This is what Congressional slow-walking looks like. This is not an accident; it is a deliberate strategy. Nadler first announced on April 29th that Mueller was supposed to testify on May 15th.
March 23: Mueller Report Issued
March 25: Nadler writes letter requesting report by April 2
March 29: Barr refuses to release un-redacted report
March 29: Nadler says April 2 still stands
April 2: Barr refuses to release un-redacted report
April 3: The House Judiciary Committee votes to authorize subpoena for report
April 3: Barr refuses to release un-redacted report
April 18: Nadler issues subpoena for report to be delivered May 1
April 29: Nadler targets May 15 for Mueller to testify
May 1: Barr refuses to release un-redacted report and misses subpoena deadline
May 3: Nadler sends a “counter-offer” letter with May 6 deadline
May 6: Barr refuses to release un-redacted report
May 6: House Judiciary Committee schedules vote to hold Barr in contempt on May 8
May 6: Barr refuses to release un-redacted report; DOJ Invites Nadler To “Negotiation”
May 7: Trump and Barr declare Report covered by Executive Privilege
May 8: House Judiciary votes to hold Attorney General Barr in contempt
May 9: Pelosi refuses to schedule full House vote on Contempt motion
May 9: Barr Jokes About ‘Record’ Contempt Vote in speech at DOJ
May 10: Nadler says Mueller will not appear on May 15
May 11: Nadler sends an “offer to compromise” letter to Barr
May 15: Barr jokes with Pelosi: 'Did you bring your handcuffs?'
May 17: Nadler delays Muller testimony until June
May 22: Still no House vote scheduled on Contempt motion
May 23: Nadler says Muller wants to testify “privately”
May 28: Mueller resigns. Pelosi still has not scheduled vote on Barr Contempt Motion
May 31: Nadler said that he still wants Mueller to testify
June 3: House vote Scheduled June 11 for on Barr Contempt Motion
June 4: Hoyer reports Nadler is talking to Mueller
June 4: Barr requests to re-open Mueller Report talks if Contempt Motion vote is stayed
June 6: Nadler says could issue a subpoena to Mueller within two weeks
June 10: Barr refuses to release un-redacted report; Nadler agrees to see what Barr deems “most important”
June 25: Mueller agrees to testify in public on July 17.
July 12: Congress still has not seen unredacted Muller Report
July 12: Politico and CNN report Mueller testimony delayed by at least a week.