assert.strictEqual(helper.pageIndex(0), 0, "pageIndex(0)")
                                    ^   ^
                                    |   This is the index of the page that the item would be on
                                    |
                                    This is the index of the item in the collection

helper.pageIndex(0) Will find the index of the page which includes the item at index 0 of the collection (In this case, 1). The return value being 0 means that 1 is included on the page with index 0 (the first page).

On the Typescript test the collection has no "0" item.

const collection = [
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
    22, 23, 24,
  ]

this test:

  assert.strictEqual(helper.pageIndex(0), 0, "pageIndex(0)")

there are no 0 item on the given collection.

so I thought it should return as "-1" ?

I also have the same error in don't know why

Punctuations mark are not limited to what you've considered so far...

I am using TS

TSError: ⨯ Unable to compile TypeScript:
test.ts:2:23 - error TS2306: File '/workspace/default/solution.ts' is not a module.

2 import { greet } from "./solution";
~~~~~~~~~~~~

Solved. Closing.

Fork and fix waiting for approval.

I'm not familiar with chai so not claiming this is the best fix, but replacing the basic tests with this gets it working

    assert(rgb(0, 0, 0) === "000000", 'expected 0,0,0 to equal 000000');
    assert(rgb(0, 0, -20) === "000000", 'expected 0,0,-20 to equal 000000');
    assert(rgb(300, 255, 255) === "FFFFFF", 'expected 300,255,255 to equal FFFFFF');
    assert(rgb(173, 255, 47) === "ADFF2F", 'expected 173,255,47 to equal ADFF2F');

Error test failed:
expected 'ihGVsgaZUsgSPay pKISbPhpcOTmAXIdpdIay…' to equal 'ihGVsgaZUsgSPay pKISbPhpcOTmAXIdpdIay…'

I check the strings:
console.log("ihGVsgaZUsgSPay pKISbPhpcOTmAXIdpdIay…" == "ihGVsgaZUsgSPay pKISbPhpcOTmAXIdpdIay…") // true;

How can I make the "Random test failed error" to show the complete words?

Same.

WHen I try to Test on Typescript I get an error:

TSError: ⨯ Unable to compile TypeScript:
test.ts:7:5 - error TS2552: Cannot find name 'Test'. Did you mean 'test'?

7 Test.assertEquals(rgb(0, 0, 0), "000000")