Real Asteroid Doom

In March NASA, FEMA, Space Force, Johns Hopkins, numerous other agencies ran an Asteroid Impact Simulation in which they discovered an asteroid that was going to hit earth in 6 months time:

[link to www.nasa.gov (secure)]

Fast forward 6 months to right now and NASA's DART spacecraft is due to attempt to deflect asteroid Didymos on Sept. 26th:

[link to www.newscientist.com (secure)]

As you can see from NASA Jet Propulsion Labs NEO orbit simulator this asteroid is heading very close:

[link to ssd.jpl.nasa.gov (secure)]

If it were just a "test" why would they test on objectS that are 2560ft diameter and 520ft diameter that are actually heading straight for us and possibly make them hit us on accident?

Didymos is a binary asteroid with a satellite in its orbit. The minor-planet moon, named Dimorphos,[13] moves in a mostly circular retrograde orbit[14] with an orbital period of 11.9 hours.[7] It measures approximately 160 metres (520 ft) in diameter compared to 780 metres (2,560 ft) for its primary (a mean-diameter-ratio of 0.22).

This is a binary pair of 2 asteroids heading at us, the main one is 1 kilometer diameter the smaller 520ft. According to the JPL simulator October 3rd will be the closest approach. With the DART craft impacting it at full speed on Sept 26th, 1 week prior.