Learn how to write simple tests

Ruby
1

Hello,

Im now trying to do the first exercises of codewars.
The exercises are not a problem.

As I example I use the hello world programm.

I can write

def greeter
puts “Hello World!”
end

But how on earth can I make a test-case for this using for example
assert ?

Roelof

2

On Mon, May 26, 2014 at 10:44:13PM +0200, Roelof W. wrote:

But how on earth can I make a test-case for this using for example assert ?

You can test that the greeter method returns hello world, on ruby
1.9.3+ like this (run ruby greeter_test.rb):

# greeter.rb
def greeter
  "Hello World!"
end

# greeter_test.rb
require "minitest/autorun"
require_relative "greeter"

class SimpleTest < Minitest::Unit::TestCase
  def test_greeter
    assert_equal greeter, "Hello World!"
  end
end

Testing that it calls puts with the “Hello World!” args is more
difficult.

3

On Monday, May 26, 2014 10:44:13 PM Roelof W. wrote:

puts "Hello World!"

end

But how on earth can I make a test-case for this using for example assert ?

Roelof

It is easy with -

assert_equal “Hello World!”, greeter

4

Amadeus F. schreef op 26-5-2014 22:59:

 # greeter_test.rb

difficult.

hmm ,
When I do this solution I see this eror :
NoMethodError: undefined method `require’ for main:Object

when I do the assert_equal line alone I see this error :
NoMethodError: undefined method `assert_equal’ for main:Object

Roelof

5

Which ruby version are you using?

On 2.1.1 it runs fine.

6

In Rspec you can describe it like this:

<<FILE
require ‘rspec’

def hello
puts “hello world”
end

describe “hello” do
it “should print to $stdout ‘hello world\n’” do
@stdout_orig, $stdout = $stdout, StringIO.new
hello
expect($stdout.string).to eq(“hello world\n”)
end
end
FILE

Run the example spec with rspec FILE

7

Mistral CONTRASTIN schreef op 26-5-2014 23:40:

If you are doing it in codewars the chances are they undefined require. The
testing advice here is given for normal execution.

Mistral

On 26 May 2014, at 22:20, Roelof W. [email protected] wrote:

Im working on codewars. I will try to ask them for some help.

Roelof

8

If you are doing it in codewars the chances are they undefined require.
The testing advice here is given for normal execution.

Mistral

9

Mistral CONTRASTIN schreef op 26-5-2014 23:40:

If you are doing it in codewars the chances are they undefined require. The
testing advice here is given for normal execution.

Mistral

On 26 May 2014, at 22:20, Roelof W. [email protected] wrote:

Thanks,

Can anyone help me figure out why I see here a syntax error :

class Testgreeter > Test:Unit:TestCase

 def test
    assert_equal("Hello World!", "output is not Hello World")
 end

end

Roelof

10

On 27 Μαϊ 2014, at 09:31 , Roelof W. [email protected] wrote:

Can anyone help me figure out why I see here a syntax error :

class Testgreeter > Test:Unit:TestCase

Try: class Testgreeter < Test:Unit:TestCase

def test
assert_equal(“Hello World!”, “output is not Hello World”)
end
end

Roelof

Panagiotis (atmosx) Atmatzidis

email: [email protected]
URL: http://www.convalesco.org
GnuPG ID: 0x1A7BFEC5
gpg --keyserver pgp.mit.edu --recv-keys 1A7BFEC5

“As you set out for Ithaca, hope the voyage is a long one, full of
adventure, full of discovery […]” - C. P. Cavafy

11

Panagiotis A. schreef op 27-5-2014 9:41:

Thanks,

Roelof

Changed it and still the syntax error message.

Roelof

12

Oh…
“:” → “::”

Try this code:
class Testgreeter < Test::Unit::TestCase
end

2014-05-27 11:46 GMT+04:00 Roelof W. [email protected]:

13

??? ??? schreef op 27-5-2014 10:33:

Oh…
“:” -> “::”

Try this code:
class Testgreeter < Test::Unit::TestCase
end

found it after a little bit trying.

the right answer is :

but now I have this :

def no_odds( values )
values.select { |x| x.even?}
end

and these test cases :

Test.assert_equals([2] , no_odds([2]))
Test.assert_raise(NoMethodError , no_odds([“a”]), “Er bestaat geen ?even
voor een string”)

Still I see this error message :

NoMethodError: undefined method `even?’ for “a”:String

NoMethodError: undefined method `even?’ for “a”:String

How can I take care that my error message is shown or even that there is
no error message too seen as I run the tests.

Roelof

14

On Tuesday 27 May 2014 11:50:15, Roelof W. [email protected] wrote:

How can I take care that my error message is shown or even that there is
no error message too seen as I run the tests.

I think you confuse the reason for a unit test with a syntactic test.
The unit
test asserts that your syntactic correct code produces the desired
results.

Basically, your code:

Test.assert_raise(NoMethodError , no_odds([“a”]))

Says this: “I don’t trust the Ruby Interpreter, so I want to write a
test
where I check whether the interpreter finds out that there’s no #even?
for a
string or not”. This is not what unit testing is supposed to do.

If you had extra safeguards in your code, you could check them. For
example,
consider this:

—%<—
def no_odds(values)
return [] unless values.class == Array
values.select { |x| x.respond_to? :even? && x.even?}
end
—>%—

Now you could test whether your code works right:

—%<—
assert_equal [], no_odds(2)
assert_equal [2], no_odds([1, 2, “a”, “c”, 3])
—>%—

HTH

  --- Eric
15

I don’t know ‘even?’ method.
Look here about all methods of String class:

2014-05-27 13:50 GMT+04:00 Roelof W. [email protected]:

16

Excuse the typo:

On Tuesday 27 May 2014 15:11:54, Eric MSP Veith
[email protected]
wrote:

—%<—
def no_odds(values)
return [] unless values.class == Array
values.select { |x| x.respond_to? :even? && x.even?}
end
—>%—

Should be:

—%<—
def no_odds(values)
return [] unless values.class == Array
values.select {|x| x.respond_to?(:even?) && x.even? }
end
—>%—

Note the parentheses.

--- Eric
17

Curious. How do you test a function embedded in another function?