Good article covering not only the imminent test of SN15 but those of SN16 to 20 and BN2 and 3 and orbital launch pad preparations.
https://www.nasaspaceflight.com/2021...a-vindication/
Starship SN15 prepares for flight following major NASA vindication
Starship SN15 is expected to undergo a Static Fire test as early as Tuesday to clear the path for a test flight no earlier than Wednesday as SpaceX’s rapidly reusable interplanetary launch and landing system gained a massive sign of NASA approval – and a ton of government cash to boot.....
With the vehicle arriving at the launch site a week ago, SN15 underwent proof testing events before Raptor installation, allowing Thrust Rams to test the Thrust Puck, one of the other modifications that will debut with SN15. During this process,
SN15 was filled with ambient gaseous nitrogen before the cryogenic testing with liquid nitrogen completed proof testing, including the Header Tanks that play a vital role in the landing sequence.
The three Raptors (SN54, SN61 and SN66 - sporting the green nozzles that have been observed during testing at SpaceX McGregor - then rolled to the launch site for installation. As previously noted by Elon Musk, all three are upgraded engines.
Installation tasks began ahead of the weekend, with the goal of readiness for the opening Static Fire test window on Monday, April 19. However, that soon slipped on Sunday to a NET (No Earlier Than) of Tuesday for the Static Fire test.
Once the Static Fire test has been completed, SpaceX will conduct a data review. On several previous occasions, the data has called for an engine swap. As such, a clean data review ahead of the Launch Readiness Review (LRR) would be a step forward for the Raptors.
While the earliest launch opportunity is now Wednesday, SN15’s flight is still waiting for the final green light from a documentation standpoint, which will come from the FAA. As of Sunday the FAA classed that approval as “pending”.
Additional factors in play this week for launch operations will be local weather conditions......