Euro NCAP tests aren't mandatory, they're voluntary.
"The European New Car Assessment Programme (Euro NCAP) is a European voluntary car safety performance assessment programme (i.e. a New Car Assessment Program) based in Leuven (Belgium) formed in 1996, with the first results released in February 1997."
"Euro NCAP is a voluntary vehicle safety rating system created by the Swedish Road Administration, the Fédération Internationale de l'Automobile and International Consumer Research & Testing, backed by 14 members, and motoring & consumer organisations in several EU country. They provide European consumers with information regarding the safety of passenger vehicles. In 1998, operations moved from London to Brussels."
"Euro NCAP's ratings consist of percentage scores for Adult Occupant, Child Occupant, Vulnerable Road Users and Safety Assist and are delivered in the overall rating of stars, 5 being the best and 0 being the worst.
5 star safety: Overall excellent performance in crash protection and well equipped with comprehensive and robust crash avoidance technology
4 star safety: Overall good performance in crash protection and all round; additional crash avoidance technology may be present
3 star safety: At least average occupant protection but not always equipped with the latest crash avoidance features
2 star safety: Nominal crash protection but lacking crash avoidance technology
1 star safety: Marginal crash protection and little in the way of crash avoidance technology
0 star safety: Meeting type-approval standards so can legally be sold but lacking critical modern safety technology"
https://en.wikipedia.org/wiki/Euro_NCAP