numoonchld / testing-ruby-with-rspec

Workbench for Udemy course - https://www.udemy.com/course/testing-ruby-with-rspec/

Setup

• rbenv versions: lists all ruby versions managed by rbenv
• ruby -v: shows active dir ruby set by .ruby-version file
• gem -v: shows the ruby gem version manager version

Install rspec

• gem install rspec

Initialize rspec dir structure

• rspec --init

Notes

• example group block:

  RSpec.describe 'Card' do
  
  end

• examples are tests that sit inside an example group

  • use it blocks for examples themselves in the example group block
  • specify is an alias for it

• expect is an rspec method to set expectations within an example

  • these expect statements are called assertions

• a single example can have multilpe assertions/expectations

To run the tests

• three ways:
  1. run all tests in the root dir and the nested dirs i.e. the entire project by simply doing rspec in the CLI
  2. do rspec spec/card_spec.rb to run all test groups in an individual file
  3. do rspec ./spec/card_spec.rb:3 i.e. with the line number to run only that line's example

Mutation and instance variables

• be careful of mutation of variables in the sequence of test example execution
  • sometimes it makes more sense to have isolated duplicate instance varible creation in examples

Hooks

• code that runs automatically at the time of test suit execution

    before do
      ...
    end

  is the same as

    before(:example) do
      ...
    end

  • other parameters that before can take are :suit and :context

• after is another hook

let method

• useful to reduce duplication of instance varibles for each example
  • will be the go to method for reducing duplication
  • let is a way to memoize (cache) something given to it

  let(:card) { Card.new('Ace','Spades')}

• let instanciates a new item specifed before each example (i.e. it block)
  • let by default implments lazy-loading
    • i.e. creates a card only at the time it needs to exist
    • let!() bypasses lazy loading

Custom error message for assertions

• .to takes a second argument (a string) that is the message to show when the assertion fails

describe/context

• they are aliases of each other
• while it/specify should be matter of fact statements
  • more abstract ideas should use describe/context
  • do not try to stuff complex scenario descriptions in an it (example's) docstring
• use as many nested describe/context as necessary to structure the test in a readable manner

RSpec helpers

• subject:

  • implicity an instance of the class passed to RSpec.describe
  • explictly can be called with a do..end block to lazy load an explicit definition of an instance of the described class

• described_class:

  • dynamically refers to the class passed in as an argument to RSpec.describe

• is_expected:

  • one liner assertion with the it keyword
  • utilizes the subject defined directly

  RSpec.describe 'shorthand_syntax' do
    subject { 5 }
  
    context 'with one-liner syntax' do
      it { is_expected.to eq 5 }
    end
  end

Shared Examples

• RSpec.shared_examples to create shared examples - in a do..end block
• include_examples - to call the shared examples
  • refer to by the docstring used to define the shared examples block

Shared Context

• RSpec.shared_context to create shared context - in a do..end block
• include_context to load shared context
  • refer to by definiton docstring

eq, eql, equal/be

• eq: checks for value sameness with type coercion
• eql: checks for value sameness without type coercion
• equal/be: checks for same memory location (obviously along with value sameness)

Predicate methods

• methods with ? at the end of a method name

  • it always returns a boolean

• the ? is not a technical specification per-se but a popular community standard

• examples

  puts 0.zero? # true
  puts 15.zero? # false
  
  puts 2.even? # true
  puts 3.even? # false
  
  puts 3.odd? # true
  puts 2.odd? # false
  
  puts [].empty? # true
  puts [1, 2].empty? # false

Predicate matcher

• be_<predicate_method_name>

Example

RSpec.describe 'predicate methods and predicate matchers' do
  it 'can be tested with Ruby methods' do
    result = 16 / 2
    expect(result.even?).to eq true
  end

  it 'can be tested with predicate matchers' do
    expect(16 / 2).to be_even
    expect(15).to be_odd
    expect(0).to be_zero
    expect([]).to be_empty
  end

  describe 0 do
    it { is_expected.to be_zero}
  end
end

Truthy and falsy values

• in Ruby land, only two entites are falsy
  • false
  • nil
• eveything else is truthy
  • strings, and empty strings
  • arrays, and empty arrays
  • numbers, positive and negative, and 0
  • hashes and symbols