Code Coverage Has a Blind Spot

Sunday, December 31st, 2023

Here’s the coverage report on a recent PR of mine:

All modified and coverable lines are covered by tests ?

    Comparison is base (a765aef) 85.95% compared to head (fe02e1b) 85.95%.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #546   +/-   ##
  Coverage     85.95%   85.95%           
  Complexity     3480     3480           
  Files           230      230           
  Lines          8225     8225           
  Branches        960      960           
  Hits           7070     7070           
  Misses          865      865           
  Partials        290      290           

Precisely identical. What happened? Did I change a comment? Well, no. In fact I added tests for
situations that were not currently covered, so why didn’t coverage increase?

Why Python is Better than Java

Sunday, December 10th, 2023

Reason 1: Mocking.

unittest.mock, Python’s mocking framework is so much more powerful than EasyMock, Mockito, or any other Java mock framework I’ve ever used. You can replace any method you like with essentially arbitrary code. No longer do you have to contort APIs with convoluted dependency injection just to mock out network connections or reproduce error conditions.

Instead you just identify a method by name and module within the scope of the test method. When that method is invoked, the actual code is replaced with the mock code. You can do this long after the class being mocked was written. Model classes do not need to participate in their own mocking. You can mock any method anywhere at any time, in your own code or in dependencies. No dependency injection required. You can even mock fields.

By contrast Java only lets you mock objects (not methods) and only when you have an available API to insert the mock in place of the real thing.

Reason 2: None is its own type.

Happy 20th Birthday Java!

Thursday, May 21st, 2015

Happy 20th Birthday Java! Next year I’ll buy you a drink. InfoWorld has published some of my thoughts on the occasion, “Java at 20: How it changed programming forever”.

Why java.util.Arrays uses Two Sorting Algorithms

Saturday, March 30th, 2013

java.util.Arrays uses quicksort (actually dual pivot quicksort in the most recent version) for primitive types such as int and mergesort for objects that implement Comparable or use a Comparator. Why the difference? Why not pick one and use it for all cases? Robert Sedgewick suggests that “the designer’s assessment of the idea that if a programmer’s using objects maybe space is not a critically important consideration and so the extra space used by mergesort maybe’s not a problem and if the programmer’s using primitive types maybe performance is the most important thing so we use the quicksort”, but I think there’s a much more obvious reason.

Why Functional Programming in Java is Dangerous

Sunday, January 20th, 2013

In my day job I work with a lot of very smart developers who graduated from top university CS programs such as MIT, CMU, and Chicago. They cut their teeth on languages like Haskell, Scheme, and Lisp. They find functional programming to be a natural, intuitive, beautiful, and efficient style of programming. They’re only wrong about one of those.