99-problems in Java 8, Scala, and Haskell (github.com)

I think you misread that bug report.

   >Closing this issue since there are no plans to include direct dependencies on third-party assertion libraries within JUnit 5.

The OP shows examples assertions using JUnit 4 and hamcrest assertThat. The OP could use the builtin assert for all I care but I sort of got the gist they were trying to show the canonical approach. This is not to critique but rather to inform.

  package com.shekhargulati.ninetynine_problems._02_arithmetic;

  import java.util.stream.LongStream;

  /**
   * (**) Determine whether a given integer number is prime.
   */
  public class P31 {

    public static boolean isPrime(long number) {
        return !LongStream.rangeClosed(2, Math.round(Math.sqrt(number))).anyMatch(n -> number % n == 0);
    }
  }

  $ find ./java8 -name \*.java | xargs wc -c | tail -1
    123903 total
  $ find ./scala -name \*.scala | xargs wc -c | tail -1
     80516 total
  $ find ./haskell -name \*.hs | xargs wc -c | tail -1
     11234 total