The Clojure version is almost certainly broken.

I just can 't see how the expected output in the random tests make sense.

Given inputs

("zPEJS" "BFPxI" "," "," "," "," "vFhKk" "," "," "," "," "," "RHFQh" ".")

It expects the result to be:

"zPEJS BFPxI, ,, , vFhKk, ,, ,, RHFQh."

This section makes no sense
BFPxI, ,, , vFhKk

Another example:

Input

("NkVcr" "," "," "DlWOv" "beeOm" "," "WYCCh" "," "," "kfaEC" "IeGwS" "xellI" "." ".")

Expected:

"NkVcr, , DlWOv beeOm, WYCCh, , kfaEC IeGwS xellI."

Why the spaces between the commas?

Another example:

Input
("fdNXT" "," "iiUuU" "," "," "," "," "," "," "xDLAz" "," "," "eywFI" "." ".")

Expects this bizarness:
"fdNXT, iiUuU, ,, ,, , xDLAz, , eywFI."

What is going there? A Space after the comma, then 2 commas without a space, then a space, then 2 more without a space, then a space?

It looks like any number of commas, has to be broken up into blocks of 2, and be surrounded by spaces. This is wrong.

This is clearly broken.

If it wants every pair of commas to treat the 2nd comma like a word, this makes no sense. A comma isn't a word.

But this one breaks the above:

Here the input is:

("Gjnjv" "lXgCV" "," "," "," "," "," "," "," "RtzYV" "ewWZE" "." ".")

ANd it expects:

"Gjnjv lXgCV,, ,, ,, , RtzYV ewWZE."
            ^^ why no space here between the 2 commas?

IT seems different to the example above. Is it something to do with odd / even combinations of commas?

Why not write inputs in tests?

No test cases composed of multiple sentences

Can someone explain why this:

["SWmBK" "," "," "," "," "aXeok" "," "EoULa" "," "," "dWnzl" "jckXr" "," "rTDdP"" yReZA" "." "." "."]

Should result in

"SWmBK, ,, , aXeok, EoULa, , dWnzl jckXr, rTDdP yReZA."

Why the space afte rthe first comma, but no space between ,, but then a space after 3rd comma and then space after 4.

This is in clojure

No random tests in JavaScript (at least).