Underscores shouldn't be used in googletest test names

[tiagoshibata]

Describe the bug
Use of underscores in test case names (e.g. TEST(DateTimeTransformer, Past_1976_Nov_17__12_27_04)) in googletest is not recommended, since it has a few gotchas (https://github.com/google/googletest/blob/master/googletest/docs/faq.md#why-should-test-suite-names-and-test-names-not-contain-underscore). Furthermore, some tests (such as TEST(DateTimeTransformer, Past_1976_Nov_17__12_27_04)) have double underscores, which are reserved to be used by the compiler and standard library. It's not a big issue and unlikely to break, but it's not standards conforming and, quoting googletest's docs:

If you violate the rule, there may not be immediate consequences, but your test may (just may) break with a new compiler (or a new version of the compiler you are using) or with a new version of googletest. Therefore it's best to follow the rule.

Urgency
N/A

System information
N/A

To Reproduce
Files such as onnxruntime\test\automl_ops\datetimetransformer_test.cc have a bunch of underscores in test names.

[snnn]

@yuslepukhin Please take a look

[skottmckay]

If I understand the FAQ correctly you can use a single underscore as long as it's not the first character in the test name and followed by an upper case character. I don't believe we have any invalid usage of a single underscore based on that.

The usage of a double underscore should be easily fixed.

[tiagoshibata]

If I understand the FAQ correctly you can use a single underscore as long as it's not the first character in the test name and followed by an upper case character

It's more restrictive. Single underscores:

• Can't be the first character in a test suite name if followed by an upper case character
• Can't be the first character in a test name
• Can't be the last character of a test suite name or test name

And it's tricky to use since _ is used as separator between the test suite name and test name (so TEST(Time, Flies_Like_An_Arrow) and TEST(Time_Flies, Like_An_Arrow) generate the same class name and a compilation or linking error). Since these rules are awkward, their recommendation is to simply not use _.

I opened the issue to raise awareness of this (on our porting of WinML we're following their recommendation). Fixing the use of double underscores and keeping the safe usages of single underscores sounds fine to me, just be aware of the possible duplicate class name issue :)