One, Two, Three, Four. I thought I understood the damn things. And then it turns out they have ‘lifestyle choices’ and Mr. One says ‘you know, I just don’t FEEL like an Integer’ and suddenly they are making ‘changes’ and you’re alone with the Xbox, a pound of bacon, and nothing but tears.

Floating Point Numbers

I’m talking numbers in Ruby right now, but I’m shaken to the core. Floating numbers are numbers! They should work right! They should ADD UP! Now, a floating point number is at least equal to itself. This passes:

assert_equal(0.1, 0.1)

But this doesn’t:

assert_not_equal(0.1, 0.4-0.3)

You’d think 0.1 == 0.1 but you’d be wrong! You see, 0.1 is only an approximation of the value stored by the floating point system in binary. 0.3 is an approximation, and 0.4 is an approximation. And when they are mathed, they don’t approximate out equally. There’s a loss of precision. It’s pretty close. This passes:

expected_float = 0.1

actual_float = 0.4-0.3

assert ( (expected_float - actual_float).abs <= 0.00000005 )

…it’s just not exact. It’s wrong over in C# too.

[Test]

public void FloatTests()

{

Assert.AreEqual(0.1f, 0.3f - 0.2f);

}

Goes boom:

Modulus

What’s a modulus? First off, I thought it was the number you get when you use the mod operator in a language…but it’s not. The modulus is actually the number you ‘divide’ by in a mod operation. The result is technically called the remainder.

Now the way I learned it, the mod operation is a lot like making change. If I have 1453 copper pieces (cp) and one silver piece (sp) is 100 coppers, then I find out how many silvers I have with simple division. This passes in C#:

int copper
= 1453;

int silver
= copper / 100;

int change
= copper % 100;

Assert.AreEqual(14, silver);

Assert.AreEqual(53, change);

And in Ruby:

copper = 1453

silver = copper / 100

change = copper % 100

assert_equal 14, silver

assert_equal 53, change

It’s all good so far, right? But what if I owe money? What if my initial total is –1453 ? I owe 14 silvers and 53 coppers, right? Well, yes. And that’s what C# shows. –14 silver and –53 coppers. But not Ruby:

copper = -1453

silver = copper / 100

change = copper % 100

assert_equal -15, silver

assert_equal 47, change

You owe 15 silver. And when you pay…you’ll get 47 copper back. If you want the C# (C++, C, etc) results, you’ll need to use positive numbers and handle the negative yourself.

I’ve been scratching my head around this, and it really seems like it’s an equally valid way of the numbers. The math people have both definitions lying around. And some cases have this method make more sense. Imagine you’re trying to find out what O’Clock it is. You have your hours variable and you use the mod operator. HOURS % 12. That works just fine, until you go negative. What if you wanted to know what O’Clock it was 143 hours ago? If it’s noon, and you’re using Ruby, –143 % 12 gives you the right answer.

I guess the accountants are right. “What do you want the numbers to be?”

In my first and second post on the idea of learning Ruby through writing tests, I showed the basics of learning a language using the TDD tools. Since that start, I’ve found some great work others have done along these lines that you can use to play with the skills you’re learning and test yourself against some real problems.

First, the Ruby Koans by Jim Weirich are a comprehensive set of ‘learning tests’ that can teach you or quiz you on what you’ve learned of Ruby so far. Each time you pass a test, it points you to the next thing you need to fix. Truly TDD learning!

I was a bit put off when I first found this set, since it seems so much like a shortcut, but there’s no reason I can’t play with Jim’s tests as well as write my own, now is there?

Second, there’s the Ruby Quiz, which looks to be a great place to get a graduate education in your Ruby skills. The quiz isn’t being added to anymore, but the challenges are just awesome and they have reference solutions from people who have solved them before you. Once you’ve solved one, you can find so many ways of learning a better way. Talk about erudition!

In my recent post, I started sharing some of the fun of learning Ruby using Test-Driven techniques to learn the language features and document what you are learning as you go.

There are several advantages of learning the language this way. It flexes your brain in ways that just reading the book or typing in the sample code doesn’t. Once you’re done, you have some running, organized code that you can refer back to. Also, when you upgrade your language, or change which platform you run it on, you can run your suite of learning tests. Find out if Ruby 1.9 is different from 1.8…and how. Are there implementation differences between linux Ruby and Iron Ruby? You’ll know.

Today, I’d like to cover the additional assert variants available in the Test::Unit module, and talk about using an IDE.

Last time, we covered the assert method for testing truth. But there are lot more things you can test!

• assert – Tests the truth of an expression
• assert_block – Tests that the return value of a code block is true
• assert_equal – Tests that two values are equal
• assert_in_delta – Tests two floats with tolerance for floating point error (read up on this one! it’s a doozy)
• assert_instance_of – Tests that an object is an instance of a class
• assert_kind_of – Tests that an object is of a class, or a subclass, or implements the kind
• assert_match – Test using a regular expression
• assert_nil – Tests the nil-ness of the expression
• assert_no_match – A not test
• assert_not_equal – A not test
• assert_not_nil – A not test
• assert_not_same – A not test
• assert_nothing_raised – A not test
• assert_nothing_thrown – Not a test. Just kidding.
• assert_operator – I don’t get this one. Well, I’m still learning!
• assert_raise – Tests that the code block raises a given exception
• assert_respond_to – Tests that an object has a named method defined
• assert_same – Tests that both values are the same object instance
• assert_send – Another one to learn on. Looks like it tests a method call?
• assert_throws – Looks like another type of exception handling.

With this group of methods, it should be rather easy for you to write some nice, readable tests as you learn things up. One interesting one is assert_same, which can prove that all values of True are really the same instance. Also, when you write a test that fails by raising an exception, use assert_raise to document that. You should have a test that shows what happens when you divide by zero, and one that shows what happens when you use an uninitialized variable.

Using an IDE

Most of the ‘True Ruby Folk’ believe with all their flinty hearts that you shouldn’t need anything more than a charred and pointed stick to write excellent Ruby. They are probably right. On the other hand, a good IDE can be like a coding video game and make the process so much more colorful and fun. I’ve sure found that JetBrains’ new RubyMine IDE has made my early Ruby coding a bit of clicky goodness.

Creating a new test class is really easy. You just add the file to your project:

You get a fully fleshed and voluptuous test class ready for you to have your way with it.

And while you’re learning the language, it’s really nice to have some code completion features so that you can figure out the rest of what you’re typing without going mad switching between windows.

All that and it’s not going to break the bank. Just $99! Give it a try.

I hope you’re keeping up with your test writing. I’ve got 168 assertions testing language features and I’m just through the primitives and variable types.

How many tests can you write?

You may not have realized it, but learning Ruby is like being attacked by a bunch of ADD Buddhist Monks. They’ll jump into your living room, raving and excited, and do back flips while telling you how Zen and relaxing development should be. It’s weird.

Once we’ve medicated the frenetic relaxation, though, it’s really evident that there a lot of good ideas to be found in this community. The latest that I’ve discovered is Test-Driven Learning.

What this means to me is that I can FINALLY stop writing ‘Hello World’ programs. Languages have print or printf or puts commands—we can stop being thrilled by that now. Ok? Let’s just write Tests! If we can make test Assertions, we can kick the tires of each new piece of language syntax we learn as we learn it without creating silly, baroque programs to host them.

Lets start out by discovering the shortest syntax to use the language’s testing framework. The one built into Ruby is Test::Unit. This is easy in Ruby. You need a ‘require’ line and to subclass the test fixture class.

require "test/unit"

class TestTest
< Test::Unit::TestCase

def test_tests

assert true

end

end

That’s easy. And now you can assert things. Like ‘true’. Save that in a file, like ‘test.rb’ then execute it with the ruby command line.

C:\Users\josh\Desktop> ruby test.rb

Loaded suite test_test

Started

.

Finished in 0.001
seconds.

1 tests, 1 assertions, 0 failures, 0 errors

From here on out, just start adding ‘assert’ lines as you discover things about Ruby. Since we started with ‘true’, maybe some asserts on Truth would be a good start. I wonder which of these will pass and which will fail? If you know Perl, Javascript, or C# your preconceptions will be different.

assert true

assert false

assert 'True'

assert ""

assert 0

assert 1

So little code, and now you can curl up with your favorite Ruby howto book and spend a warm afternoon pondering the nature of Truth. Exciting eh? Well calm down! You don’t need to be a crazy Zen guy. Just do some learning.

Resources:

• “Ruby Learning Test #1: Are You There, World?” by Mike Clark
• Why’s (Poignant) Guide to Ruby
• Test::Unit at ruby-doc

There’s a piece of advice that floats around, apparently from the Pragmatic Programmer, which goes like this:

Learn One New Language Each Year

I made a good start at Ruby last year, but got derailed by new exciting things over in the .NET world. This year is definitely the one.

I’ve got two reasons:

First, I’m really excited about programming phone systems with Adhearsion.

Second, I’ve realized that all the cool kids over at Microsoft spent the last 3 years getting excited about Ruby. Not only are they developing their own Ruby runtime, but the dynamic features of C# 4.0 coming in VS2010 are obviously being designed to keep developers from jumping ship. We need to learn to think like Ruby coders to adapt to the new problems coming down the line.

One more thing…

Ruby is becoming a first-class citizen for Macintosh GUI application development. If you can write cross-platform libraries that work on the first-class frameworks on Windows, Linux, and the Mac…soon life will be nothing but champagne and swimsuit models!