3.4. Step - 04 : Add implementation and pass

Let’s add steps so that addition is successful..

• libmath.py

  The actual implementation.

  # libmath.py
  
  class libMath(object):
      def __init__(self):
          self.num1 = 0
          self.num2 = 0
          self.value = 0
  
      def doStoreNum1Num2(self, num1, num2):
          self.num1 = num1
          self.num2 = num2
  
      def doAdd(self):
          self.value = self.num1 + self.num2
  
      def getValue(self):
          return self.value
  

• features/simple-addition.feature remains as is.

  # features/sample-addition.feature
  
  Feature: Simple Addition
  
      Showcase simple addition for the BDD Book.
  
      Scenario: Addition of single digit numbers
          Given I have '1' and '3'
          When I add them
          Then The result must be '4'
  
      Scenario: Addition of double digit numbers
          Given I have '70' and '29'
          When I add them
          Then The result must be '99'
  

• features/environment.py

  Let’s add a hook to create a new libMath object before each scenario.

  # environment.py
  
  import libmath
  
  def before_scenario(context, scenario):
      """ Let's start with a new clean object before every test. """
      context.math = libmath.libMath()
  

• features/steps/steps_addition.py

  Calls the actual libMath for the expected behaviour

  # features/steps/steps_addition.py
  
  from behave import given, when, then
  
  @given(u"I have '{num1:d}' and '{num2:d}'")
  def given_i_have(context, num1, num2):
      context.math.doStoreNum1Num2(num1, num2)
  
  
  @when(u"I add them")
  def when_i_add(context):
      context.math.doAdd()
  
  @then(u"The result must be '{value:d}'")
  def then_the_result_must_be(context, value):
      actual_value = context.math.getValue()
      assert value == actual_value, "Expected %d got %d"%(value, actual_value)
  
  

With above contents, if we run behave:

behave  --no-timings --no-source

We can see that everything is successful:

Feature: Simple Addition
  Showcase simple addition for the BDD Book.
  Scenario: Addition of single digit numbers 
    Given I have '1' and '3'
    When I add them
    Then The result must be '4'

  Scenario: Addition of double digit numbers 
    Given I have '70' and '29'
    When I add them
    Then The result must be '99'

1 feature passed, 0 failed, 0 skipped
2 scenarios passed, 0 failed, 0 skipped
6 steps passed, 0 failed, 0 skipped, 0 undefined
Took 0m0.001s