That test expects false. Make sure you're reading the log right.

If Boards containing one or more zeroes are considered to be invalid solutions. then why does it expect true when I return false on a row containing [0, 1, 2, 3, 4, 6, 7, 8, 9]?

Language was Javascript.

I can't believe this hasn't been done before. I'm perplexed.

The reference solution allows that lines will be drawn moving up or left. The description does not specify this will not happen.

The tests allow solutions that only allow lines drawn moving down or right.

Set chai.config.truncateThreshold to 0, to make error messages like expected [] to deeply equal [ Array(10) ] actually report the expected value. Right now, they're pretty much useless.

Representing an array of characters as a string instead might reduce the visual clutter in the description ( and everywhere ).

Drawing only vertical/horizontal lines is much simpler than implementing a general algorithm, so I'd not call it a duplicate of katas #2 and #3. And #1 is completely different from what you're supposed to do here.

Lines should be composed of 'x' strings while empty spaces are ' '.

You have to actually describe the task. Otherwise, this statement makes no real sense.

You're right!

Fixed!!

I changed the wording, hopefully that's better.

Thanks for your feedback!

Duplicate of several more general katas;

1. Canvas Fun #1: Draw Lines
2. Bresenham's line Algorithm
3. Graphics 01: Drawing Lines

and how integers can produce anything? Is integer a function?

No random tests.

Tests produce useless error messages.

There's no reason to pass the coordinates as an object instead of an array.