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06 Testing Relationships and Scopes

ActiveSupport::TestCase

  • Rails ships with three types of tests: unit (models), functional (controllers), and integration (full MVC stack).
  • def test_: test method, 里面包含了一系列assertion
  • regular expression: 某个string是否符合某个特定格式
  • Before every test method the setup method is invoked, and afterwards the teardown method
  • Every test method makes one or more assertions about the behavior of the class under test

Unit testing assertions

assert(actual, message) # Asserts truth assert_equal(expected, actual, message) assert_in_delta(expected_float, actual_float, delta, message) assert_match(pattern, string, message) assert_nil(object, message) / assert_not_nil assert_raise(Exception, ..., message) { block ... } assert_difference(expressions, difference = 1, &block)

shoulda should have_many(:pets) 如果要test 一个 relationship非常困难（生成的是sql code），所以就用这个shoulda lib

simplecov --> coverage/index.html --检验coverage

scope -- generate segments of SQL rails db:test:preprare--create test database for you

factory--blueprint of how to create an object of a certain type 

factory :owner do
    association :user
    name {"Alex"}
    # some other attributes
    end
turtle = FactoryBot.create(:animal) --create turtle of animal type using default value turtle = FactoryBot.create(:animal, name: "Turtle")

Tests should be independent because Rails run the test cases in random order. create - delete Every test should test only one method add records to the test database --> test them (keep the test database as small as possible) 每次都是加一点然后删一点

Unit testing

  • Unit testing is done on models only
  • All models have a default test created upon rails generate model or rails generate scaffold
  • Unit tests are stored in the directory test/models within a Rails project
  • rails test:models --run just model tests
  • rails test --run all tests
  • rails test test/models/owner_test.rb -- executing a particular file
  • test coverage --gems like simple_cov
    • not perfect and especially vulnerable to false positive readings

Why testing?

  • Tests give us confidence the code works, as it should, in all cases
  • Tests helps us better understand the problem we are solving / method we are writing
  • Tests serve as a form of documentation
  • Tests serve as a form of institution memory
  • Tests make clear what performance expectations are
  • Tests identify ways in which we can clean up code and safely refactor
  • Tests save money in the long run (the Boeing answer)
  • Tests identify problems when they are easier/less costly to fix