MDL-65204 phpunit: various fixes to assertions
Namely:
- 3rd param of assertEquals() cannot be null.
- Some incorrect uses of assertNotEmpty().
- Comparing 2 strings now uses strict (===) evaluation.
Link: https://github.com/sebastianbergmann/phpunit/issues/3185
Solution here is one of:
a) Return to the previous situation, making the comparison
softer. That can achieved by forcing different types, so
float == string works.
b) Changing APIs (both forms and database return strings) to
perform some conversion to floats. That would make float
comparison (with floats or strings) to work too.
The patch here follows the a) approach. Changing all the internals
for proper float handling sounds excesive when it has been working
perfectly since ever. So we went the easier route, just getting
rid of the new === comparisons when needed by changing expectation
types to float.
