RFR: 8324672: Update jdk/java/time/tck/java/time/TCKInstant.java now() to be more robust

[Ramkumar Sunderbabu]

On Wed, 9 Oct 2024 01:10:54 GMT, Ramkumar Sunderbabu <rsunderbabu at openjdk.org> wrote:

>> test/jdk/java/time/tck/java/time/TCKInstant.java line 193:
>> 
>>> 191:         Instant test = Instant.now();
>>> 192:         long diff = Math.abs(test.toEpochMilli() - expected.toEpochMilli());
>>> 193:         assertTrue(diff < 10_000);  // less than 10 secs
>> 
>> Given arbitrary delays between the two executions; the premise of the test itself is suspect; especially if the allowed time is increased.  I think the test is supposed to be testing that the default clock for Instant.now() is the SystemUTC clock.
>> I'd expect expected to be less than or equal to test.
>> The use of math.abs allows the clock to go backwards; that might happen if the time was re-set manually.
>
> Thanks @RogerRiggs for the comments. I increased the diff allowance to absorb any compilation related delays. What would you propose here?

If your objection is primarily on Math.abs, is this ok?
`
        long diff = test.toEpochMilli() - expected.toEpochMilli();
        assertTrue(diff >= 0 && diff < 10_000);  // less than 10 secs
 `

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PR Review Comment: https://git.openjdk.org/jdk/pull/21413#discussion_r1792673474