How to use and write tests for HardMediumSoftBigDecimalScore.

[ace19wre]

So I switched to HardMediumSoftBigDecimalScore from HardMediumSoftLongScore to use the load balancing API.
All of my tests failed.

I wrapped all the penalty values by BigDecimal.valueOf(XX) to fix it

For example,

.penalize(HardMediumSoftBigDecimalScore.ofHard(BigDecimal.valueOf(20L)))

has the corresponding test

.penalizesBy(BigDecimal.valueOf(20));

which fails, the test listings output is as follows

java.lang.AssertionError: Broken expectation.
        Constraint: [************]
  Expected penalty: 20 (class java.math.BigDecimal)
    Actual penalty: 1 (class java.math.BigDecimal)

  Explanation of score (-20hard/0medium/0soft):

The -20 reflects in the score but not in the penalty, how should I correct it?
And why this behaviour?

[triceo]

Hello @ace19wre!

The behavior you describe is strange, and could be a bug.
That said, this code is fairly well tested - would you mind providing a reproducer?

[ace19wre]

Hi @triceo,

Creating a reproducer is unfortunately a bit beyond my current skills, so I’ve added you to my repository. When you have some time, could you please take a look?

I initially thought the issue might be specific to my local setup, but I’m seeing the same listings test error in the GitHub Actions workflow as well.

I also tried updating all the project dependencies, but no change.

Not only that I observed that my build from 3 weeks ago failed with same behaviour even though I was using HardMediumSoftLongScore

Thanks in advance for your help!

[triceo]

Having looked over your codebase, I think that this is a misunderstanding of the concepts around penalties and rewards. Penalty/reward for a constraint is calculated from three components:

• Number of matches, also called match count. (How many times the penalty/reward happened.)
• Match weight. (Result of applying a user-defined lambda to a match, defaults to 1.)
• Constraint weight. A user-defined Score by which to multiply the overall penalty/reward.

You can imagine the score being calculated like so (pseudocode):

var penalty = 0
foreach match:
    penalty += (match * matchWeight)
return penalty * constraintWeight

In your case:

• Match count is 1.
• Match weight is unspecified, therefore it is 1 by default.
• Constraint weight is 20hard.
• Therefore your total penalty is 1, resulting in a score of -20hard.

What you're testing in the penalizesBy(...) method is not the score - it is the penalty. Therefore the correct result is 1 and not 20.

Constraint weights are not used in this calculation, because they are dynamic and can be overridden at runtime. We have a special section in the docs describing how to test an entire constraint provider, and not just the individual constraints.