Best practice for looped JUnit test

Question

In a school assignment, I should write blackbox test for a method that returns true for a parameter < 80 and false otherwise. Currently my approach would be

for (int i = 0; i < 80; i++) {
    assertTrue(someMethod(i));
}
for (int i = 80; i <= 100; i++) {
    assertFalse(someMethod(i));
}

However, this would require 100 seperate assertions. Is there a best/better practice method? If relevant, I'm using JUnit 5 but could switch to JUnit 4 if required (it's just a school assignment after all). Regards.

Answer 1

For JUnit 5 consider the repeated test feature:

https://junit.org/junit5/docs/current/user-guide/#writing-tests-parameterized-tests

For your case you could repeat 100 times:

@ParameterizedTest
@MethodSource("args")
public void so(int argument)
{
   assertTrue((argument < 80) == someMethod(argument));
}

private static IntStream args()
{
   return IntStream.range(0, 100);
}

I would agree checking 1 - 100 is not totally necessary, just check around 80 (79, 80, 81). The only other case that might be worthwhile is checking a negative number but even that seems overkill in this case.

If you do decide to just check 79,80,81 then the ValueSource annotation is cleaner:

@ParameterizedTest
@ValueSource(ints = { 79, 80, 81 })
public void so(int argument)
{
   assertTrue((argument < 80) == someMethod(argument));
}