`AlwaysUseLowerCamelCase` reports violation for uppercase-starting test function names

[elmetal]

The AlwaysUseLowerCamelCase rule documentation states that test code is ignored (files that import XCTest or functions marked with @Test).
However, the rule still reports violations for test function names that start with an uppercase letter.

Should the fix be applied to the implementation, or should the documentation be updated to clarify that only underscores are ignored in test code, not uppercase-starting names?

Reproduction

import Testing

struct MyTests {
    // This triggers a warning even though it's marked with `@Test`
    @Test func MyTestCase() {
        // ...
    }
}

Expected behavior (if documentation is correct): No warning, because the function marked with @Test.

Actual behavior: Warning is reported. warning: [AlwaysUseLowerCamelCase] rename the function 'MyTestCase' using lowerCamelCase

Root Cause

In AlwaysUseLowerCamelCase.swift, whether a function is marked with @Test is determined by the allowUnderscores flag.

swift-format/Sources/SwiftFormat/Rules/AlwaysUseLowerCamelCase.swift

Line 119 in 02c5a88

let allowUnderscores = testCaseFuncs.contains(node) || node.hasAttribute("Test", inModule: "Testing")

The diagnoseLowerCamelCaseViolations function checks for underscores with the allowUnderscores flag.
However, the uppercase check does not consider the allowUnderscores flag:

swift-format/Sources/SwiftFormat/Rules/AlwaysUseLowerCamelCase.swift

Line 188 in 02c5a88

if (text.dropFirst().contains("_") && !allowUnderscores) || ("A"..."Z").contains(text.first!) {

[allevato]

Right. It's not spelled out in the name of the rule, unfortunately, but the intent here is to allow underscores only, since it's a common pattern for folks to write tests named like testSomeThing_doesSomeAction_whenSomePrecondition. It's not meant to allow any casing scheme.

With the benefit of hindsight, I think my preference would be to have a general FollowNamingConventions rule that enforces the right casing for more than just variables/functions—we should have also enforced that type names were UpperCamelCase. That could still have carve outs for test methods to contain underscores (with raw identifiers in 6.2, I'd rather just say we allow those and not check their contents, but we'd still need the existing carve out for older code). But I can't think of a world where we'd want to allow UpperCamelCase for a function name just because it's a test. IMO, rename the function or add a comment to disable the rule if it's that important.