test: Migrate AstCheckerTest to Junit5

[Rohitesh-Kumar-Jain]

#3919

This PR just migrates AstCheckerTest to Junit5, pure refactoring.

[Rohitesh-Kumar-Jain]

Hi migrating AstCheckerTest to Junit5 involved only 2 changes, I was wondering that should I raise PRs that are this small 😅, or should prioritize bigger tests first instead of going sequentially?

[slarse]

@Rohitesh-Kumar-Jain Yes, your recent changes have made it clear that these migrations are pretty tiny. Let's try to bunch them up a bit.

Let's try something semi-extreme: try to migrate every test class in the the spoon.reflect that does not require any extensive changes (i.e. at most swap the order of arguments to some assertion). Keep going until you've a total of ~100 changes (insertions + deletions).

[slarse]

This one is also fine, looks like @Rohitesh-Kumar-Jain is starting to get comfortable with submitting PRs :)

[Rohitesh-Kumar-Jain]

@Rohitesh-Kumar-Jain Yes, your recent changes have made it clear that these migrations are pretty tiny. Let's try to bunch them up a bit.

Let's try something semi-extreme: try to migrate every test class in the the spoon.reflect that does not require any extensive changes (i.e. at most swap the order of arguments to some assertion). Keep going until you've a total of ~100 changes (insertions + deletions).

Yes, this seems a good idea and for the test involving many changes, I will raise PRs for them separately.