Test/suite names use underscores (violates GoogleTest naming rule; ~39+ generate reserved identifiers / UB)

[IvanaGyro]

(Issue written by Claude on behalf of @IvanaGyro.)

Summary

GoogleTest's own FAQ says test suite names and test names must not contain underscores (googletest FAQ — "Why should test suite names and test names not contain underscore?"). Our test suite violates this very widely, and a subset of the violations produce reserved C++ identifiers (undefined behavior), not just style problems.

Why it matters (from the FAQ)

TEST(SuiteName, TestName) expands to a class named SuiteName_TestName_Test (the macro joins the parts with _ and appends _Test). Two failure modes follow:

1. Reserved identifiers (UB). The C++ standard reserves "any identifier that starts with _ followed by an upper-case letter, and any identifier that contains two consecutive underscores (__) anywhere." So a TestName that ends in _ (→ ..._ + _Test = ..__Test), or that already contains __, makes the generated class name a reserved identifier — undefined behavior.
2. Name collisions. Even when not reserved, different underscore placements collapse to the same class name. The FAQ's example:

   TEST(Time,       Flies_Like_An_Arrow) { ... }
   TEST(Time_Flies, Like_An_Arrow)       { ... }

   both generate Time_Flies_Like_An_Arrow_Test → conflict.

Scope in this repo (master @ 24e8cc6)

Counting TEST / TEST_F / TEST_P / TYPED_TEST macros under tests/:

• 877 of 1020 test names contain an underscore.
• 123 suite/fixture names contain an underscore (e.g. linalg_Test).
• Of the test names, the reserved-identifier (UB) subset:
  • ~39 test names end with _ → generated class has __. Examples: Trace_, Trace__str, Transpose_, Pow_, Tensor_Gemm_, Tensor_Inv_, DenseUt_InvM_, contiguous_, get_block_, get_blocks_, gpu_Tensor_Gemm_, gpu_DenseUt_Pow_, Conj__.
  • ~68 test names contain __ directly.

(Combined with underscore-containing suite names, many more class names embed __ even when the individual name doesn't end in one — e.g. suite linalg_Test + name Tensor_InvM_ → linalg_Test_Tensor_InvM__Test.)

Suggested action

• Longer term, migrate test/suite names to underscore-free CamelCase to comply with the FAQ and avoid the collision class entirely.
• This is mechanical but large (877 names); it can be done incrementally per test file. A CI lint (grep for TEST*\(.*_.*, / names with _) could prevent regressions once cleaned.