CODEWITHSUNDEEP
ruby-on-railsruby
Will Raben
Will Raben

Reputation: 107

assert_equal Syntax

I have trouble understanding a chunck of code on a book I'm reading.

Here's the code:

test "product price must be positive" do
  product = Product.new(:title => "My Book Title", :description => "yyy", :image_url => "zzz.jpg")
  product.price = -1

  assert product.invalid?
  assert_equal "must be greater than or equal to 0.01", product.errors[:price].join('; ' )

  product.price = 0
  assert product.invalid?

  assert_equal "must be greater than or equal to 0.01", product.errors[:price].join('; ' )
  product.price = 1
  assert product.valid?
end

form the ruby documentation I got:

assert_equal(exp, act, msg = nil)

Fails unless exp == act printing the difference between the two, if possible.

am I right to assume that the line:

assert_equal "must be greater than or equal to 0.01" ,

means:

assert_equal ("must be greater than or equal to 0.01", , ) #with no act or msg.

also, can someone explain what array is the following line using and what for?

product.errors[:price].join('; ' )

I can't grasp where's the array and what is the author achieving by joining.

Thanks in advance for any information.

The book is: Agile Web Development with Rails 4th Edition

Upvotes: 3

Views: 2053

Answers (1)

Prakash Murthy
Prakash Murthy

Reputation: 13077

The full assertion is in one line as follows : 

 assert_equal "must be greater than or equal to 0.01" , product.errors[:price].join('; ' )

Here, exp = "must be greater than or equal to 0.01" and act = product.errors[:price].join('; ' )

product.errors[:price] is an array, taking in multiple error messages.

Chaining .join(';') to it is making all the error messages joined together with a ';' as a separator.

In this case, there is only one error ("must be greater than or equal to 0.01") and hence the join method is just returning the same value without adding a separator. Hence the assertion should pass.

Example to illustrate the behavior of join(';') in this case:

> ['a', 'b'].join(';')
=> "a;b" 

> ['a'].join(';')
=> "a"

Upvotes: 2

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