dnd-character: chi-squared tests by keiravillekode · Pull Request #584 · exercism/zig

keiravillekode · 2026-09-15T05:00:40Z

No description provided.

github-actions · 2026-09-15T05:00:49Z

This PR touches files which potentially affect the outcome of the tests of an exercise. This will cause all students' solutions to affected exercises to be re-tested.

If this PR does not affect the result of the test (or, for example, adds an edge case that is not worth rerunning all tests for), please add the following to the merge-commit message which will stops student's tests from re-running. Please copy-paste to avoid typos.

[no important files changed]

For more information, refer to the documentation. If you are unsure whether to add the message or not, please ping @exercism/maintainers-admin in a comment. Thank you!

keiravillekode · 2026-09-15T05:09:06Z

The interface change was requested in
https://forum.exercism.org/t/dnd-character-exercise-teaches-the-wrong-lesson/82633/

kotp · 2026-09-15T08:16:49Z

+
+A correct implementation has less than a 0.01% chance of failing each test.
+
+Note that, according to the instructions, an ability score is _the sum of the three largest results out of four rolls of an unbiased d6 (six-sided die)_.


The instructions does not propose these restrictions.

Here is what the instruction document currently states:

You do this by rolling four 6-sided dice and recording the sum of the largest three dice.

There is no statement of requirement that it be an unbiased six sided die, and even states that it is not four rolls of a single die, but "by rolling four 6-sided dice", while the answer could be accomplished with a single d6 rolled four times, it is misquoting, misstating what is referenced.

Instead, we can avoid this (due to it may be changed at any time, without any downstream referencing of append file) by deferring to the instructions without mentioning specifics to this level of detail.

Perhaps the safest line would be:

"See the instructions for a definition of what an ability score is."

I see the word "above" is added to introduce "instructions" and while it can be true that it is literally "above" it is not the case for all situations (such as reviewing this append file alone). We could reference "instructions" without a geographical reference of any kind, and it would be more universally compatible with the reader's situation.

truly-not-taken · 2026-09-15T11:18:14Z

+test "random ability is distributed correctly" {
+    var prng = std.Random.DefaultPrng.init(testing.random_seed);
+    const random = prng.random();
+    var counts = [_]u64{0} ** 16;


var counts: [16]u64 = @splat(0);

truly-not-taken · 2026-09-15T11:20:36Z

+test "each character ability is distributed correctly" {
+    var prng = std.Random.DefaultPrng.init(testing.random_seed);
+    const random = prng.random();
+    var counts = [_][16]u64{[_]u64{0} ** 16} ** 6;


var counts: [6][16]u64 = @splat(@splat(0));

truly-not-taken · 2026-09-15T11:22:14Z

+test "character abilities are independent" {
+    var prng = std.Random.DefaultPrng.init(testing.random_seed);
+    const random = prng.random();
+    var counts = [_]u64{0} ** 64;


var counts: [64]u64 = @splat(0);

truly-not-taken · 2026-09-15T11:23:44Z

+
+/// The number of times each score from 3 to 18 arises among the
+/// 6 * 6 * 6 * 6 = 1296 equally likely rolls of four dice.
+const score_weights = [16]u64{ 1, 4, 10, 21, 38, 62, 91, 122, 148, 167, 172, 160, 131, 94, 54, 21 };


const score_weights: [16]u64 = .{ 1, 4, 10, 21, 38, 62, 91, 122, 148, 167, 172, 160, 131, 94, 54, 21 };

truly-not-taken · 2026-09-15T11:29:19Z

 }

 test "random ability is within range" {
+    var prng = std.Random.DefaultPrng.init(testing.random_seed);
