yep, I' ve understood something wrong.

Not a kata issue, your solution is wrong.

Can someone explain to me, how that test is possible to pass?
"'kmoprvwxyzbcde' should equal 'bodebxypdroczkmomkwov'"

kmoprvwxyzbcde has 15 letters and bodebxypdroczkmomkwov has 20 letters.
Is this a joke?
Who made those test?
There are plenty wrong test as well.

"kmocd" should equal "docdmkco"
Invalid: "kmocd" has 5 letters, while "docdmkco" has 8 letters.

"kmnoybcg" should equal "mynogkbc"
Invalid: Different lengths and different sets of letters.

"korvwzbcdh" should equal "ohkwzvodocdrobo"
Invalid: Different lengths (10 vs. 14 letters).

"kmoprvwxyzbcde" should equal "bodebxypdroczkmomkwov"
Invalid: Different lengths (15 vs. 20 letters).

"klmoqrswxyzbd" should equal "lbsxqyxdrolyydmkwz"
Invalid: Different lengths (14 vs. 18 letters).

"kmnopqsxyg" should equal "goxoonkxyppsmonyq"
Invalid: Different lengths (10 vs. 16 letters).