While we might never be able to have 100% of our code strict, we can at
the very least do it for all of our tests. This ensures that our tests
are using our API with the types as intended by the test author, and not
silently be cast to what our API requires.
* Extract DELTA() and GESTEP() functions from the Engineering class into a dedicated Comparison classes
Retain the original methods in the Engineering class as stubs for BC, but deprecate them. They will be removed for PHPSpreadsheet v2
Note that unit tests still point to the Engineering class stubs; these should be modified to use the Erf and ErfC classes directly when the stubs are removed
Adrien Crivelli
MarkBaker
Mark Baker