String Calculator - Rspec

How to write the better Rspec for the below given String calculator .  

String Calculator

The following is a TDD Kata- an exercise in coding, refactoring and test-first, that you should apply daily for at least 15 minutes (I do 30).

Before you start: 

• Try not to read ahead.
• Do one task at a time. The trick is to learn to work incrementally.
• Make sure you only test for correct inputs. there is no need to test for invalid inputs for this kata

String Calculator

1. Create a simple String calculator with a method int Add(string numbers)
   1. The method can take 0, 1 or 2 numbers, and will return their sum (for an empty string it will return 0) for example “” or “1” or “1,2”
   2. Start with the simplest test case of an empty string and move to 1 and two numbers
   3. Remember to solve things as simply as possible so that you force yourself to write tests you did not think about
   4. Remember to refactor after each passing test
2. Allow the Add method to handle an unknown amount of numbers
3. Allow the Add method to handle new lines between numbers (instead of commas).
   1. the following input is ok:  “1\n2,3”  (will equal 6)
   2. the following input is NOT ok:  “1,\n” (not need to prove it - just clarifying)
4. Support different delimiters
   1. to change a delimiter, the beginning of the string will contain a separate line that looks like this:   “//[delimiter]\n[numbers…]” for example “//;\n1;2” should return three where the default delimiter is ‘;’ .
   2. the first line is optional. all existing scenarios should still be supported
5. Calling Add with a negative number will throw an exception “negatives not allowed” - and the negative that was passed.if there are multiple negatives, show all of them in the exception message

   ---

   stop here if you are a beginner. Continue if you can finish the steps so far in less than 30 minutes.

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6. Numbers bigger than 1000 should be ignored, so adding 2 + 1001  = 2
7. Delimiters can be of any length with the following format:  “//[delimiter]\n” for example: “//[***]\n1***2***3” should return 6
8. Allow multiple delimiters like this:  “//[delim1][delim2]\n” for example “//[*][%]\n1*2%3” should return 6.
9. make sure you can also handle multiple delimiters with length longer than one char

Now time to start the rspec... Please follow the below steps.

Step 1:

 Install rspec gem 

gem install rspec

If you want to run spec file automatically. Then install the below gem.This will run the spec file whenever we update the rspec test case.

gem install guard

Then run below command to setup & run guard

guard init

guard

Step 2:

Then create a source file (string_calculator.rb) and create separate folder with the name 'spec'. And spec source file into the spec folder (string_calculator_spec.rb).

Step 3:

Now time to start coding. First we have to write rspec test case. (All the case will be failed until unless we complete the source code)

For example

require_relative "../string_calculator"
describe StringCalculator do
  context "#manipulate" do
   it "return 0 for empty string" do
    expect("".extend(StringCalculator).manipulate).to eq(0)
   end

   it "return value 1 for 1" do
    expect("1".extend(StringCalculator).manipulate).to eq(1)

   end
 end
end

Here '#manipulate' will refer it is instant method.

Step 4: 

Now time to code in source file. Whenever we code & save the source file. All the spec test case will be will execute.

For example

module StringCalculator
 def manipulate
   return to_i
 end
end

The guard will automatically execute the test case when it is updated & save the result is html in configure path. (If we configure for html out only)
If you want to run manually then use below command

rspec spec/string_calculator_spec.rb

The full source code for this exercise is available  here .

Please feel free to mail your feedback to siva.mca19@gmail.com


Thanks,

Siva.K