Thank you very much for your help! I found a typo in my code.

Random test 1: catYears=75, dogYears=16 => [14, 1]
Random test 2: catYears=54, dogYears=54 => [9, 8]
Random test 3: catYears=23, dogYears=94 => [1, 16]
Random test 4: catYears=99, dogYears=74 => [20, 12]
Random test 5: catYears=15, dogYears=14 => [1, 0]
arrays first differed at element [1]; expected:< 0> but was:< 1>
In first message I also use copy-paste, but delete tests where there is no 1 at element < 1>

Java

All is correct, but the compiler produces this error.
Arrays first differed at element [1]; expected: 0 but was: 1
Random test 4: catYears=7, dogYears=22 => [0, 1]
Random test 20: catYears=100, dogYears=15 => [21, 1]
Random test 67: catYears=61, dogYears=21 => [11, 1]
But 22 -> 1 year
15 -> 1 year
21 -> 1 year

I think it's all about input data, not a program itself.