[3.0][Testing] Stop the canonical path tests naming a drive letter

[albertlast]

Description

Follow-up to #9600, which fixed the Windows failure by naming C: in the path under test. That works — the drive comes from the input rather than the machine, so it passes on a runner whose checkout is on D: — but @live627 is right that a hardcoded drive letter is not the thing to leave in a test. It reads as an assumption even where it is not one, and it means nothing covers the branch that actually broke: on Windows a path that starts at the root but names no drive is rooted on the current one, and it was that step which turned /a/c into C:\a\c.

Splitting the two behaviours apart removes the need to name a drive at all.

Dot segments have nothing to do with the root, so the test named for them uses a relative path. There is no root to differ over and the whole result can be asserted exactly on either platform:

$this->assertSame('a' . $sep . 'c', Sapi::canonicalPath('a/./b/../c', false, false));

What the root is is worth covering on its own, so it gets its own test, and the drive is read from the working directory rather than assumed:

$drive = $sep === '/' ? '' : substr((string) getcwd(), 0, 2);

$this->assertSame($drive . $sep . 'a' . $sep . 'c', Sapi::canonicalPath('/a/./b/../c', false, false));

The review suggested a regex, which would also have removed the hardcoded letter. I went with an exact assertion instead because the expected value here is not "some drive" but a specific one — the drive the process is on — and assertSame says that, gives a real diff when it fails, and would still catch the original bug on POSIX, where a regex with an optional drive group would accept a stray letter. Happy to switch it if you would rather have the pattern.

Verified on both platforms. The suite is green on Linux, and I checked the Windows path by extracting canonicalPath(), substituting \ for DIRECTORY_SEPARATOR and running it with the working directory on D:, where all four assertions hold:

0 PASS expected a\c    got a\c
1 PASS expected a      got a
2 PASS expected D:\a\c got D:\a\c
3 PASS expected D:\a   got D:\a

composer lint is clean.

Issues References (Fixes|Related|Closes)

1. Related to SapiTest fails on Windows #9595
2. Follow-up to [3.0][Testing] Anchor the canonical path test to the root the platform actually uses #9600