Add support to stack multiple sanity functions.

[jjotero]

As we move more towards reusable tests, I think that adding support for stacking multiple sanity functions in the same test would greatly enhance test reusability.

Problem Example

Say we have a base class in a library with a general and basic sanity checking.

class BaseTest(rfm.RegressionTest, pin_prefix=True):
    ...
    @rfm.run_before('sanity'):
    def set_sanity_patterns(self):
        self.sanity_patterns = some_basic_sanity_checking

and a derived class that extends the tests and requires of some other additional sanity checking.

from library.... import BaseTest

@rfm.simple_test
class MyTest(BaseTest):
    ...
    @rfm.run_before('sanity')
    def set_sanity_patterns(self):
        self.sanity_patterns = some_more_advanced_sanity_checking

Here we would be overriding the sanity checking from the BaseTest class, and, assuming that we can't change the library's sources, the sanity checking from BaseTest is just impossible to reuse. This means that the derived class would have to rewrite code from BaseTest into MyTest to do the same sanity checking that was already implemented in BaseTest. Not ideal.

Problem solution

A new decorator that makes a function a deferred expression and flags the function as a sanity function would solve this problem. For example, if we call this decorator @sanity_function, the above can be rewritten as follows:

# The test library file
class BaseTest(rfm.RegressionTest, pin_prefix=True):
    ...
    @sanity_function
    def basic_sanity(self):
        return some_basic_sanity_checking

# The file with the derived test
from library.... import BaseTest

@rfm.simple_test
class MyTest(BaseTest):
    ...
    @sanity_function
    def my_derived_sanity(self):
        return some_more_advanced_sanity_checking

And this would make reframe run both basic_sanity and my_derived_sanity in the sanity pipeline stage. This removes the need of explicitly setting the sanity_patterns variable every time, since the decorator would just take care of that.

[jjotero]

A real example of this is the CSCS job report check, which uses the gpu burn check form the library. The job report check just needs to parse the job report output, but we would also like to know that the gpu burn output is healthy.

[vkarak]

Replaced by #1981.