Week 3 Systems Check

Classes and TDD - Lib file

class Square

  attr_reader :side

  def initialize(side)
    @side = side
  end

  def area
    side * side
  end

  def perimeter
    side * 4
  end
end

class Circle

  attr_reader :radius

  def initialize(radius)
    @radius = radius
  end

  def diameter
    radius * 2
  end

  def circumference
    ('%.5f' % (Math::PI * (radius * 2))).to_f
  end

  def area
    ('%.5f' % (Math::PI * (radius * radius))).to_f
  end
end

class Rectangle

  attr_reader :length, :width

  def initialize(length, width)
    @length = length
    @width = width
  end

  def area
    length * width
  end

  def perimeter
    (2 * length) + (2 * width)
  end
end

class RightTriangle

  attr_reader :horizontal_leg, :vertical_leg

  def initialize(horizontal_leg, vertical_leg)
    @horizontal_leg = horizontal_leg
    @vertical_leg = vertical_leg
  end

  def hypotenuse
    Math.hypot(horizontal_leg, vertical_leg)
  end

  def perimeter
    horizontal_leg + vertical_leg + hypotenuse
  end

  def area
    (horizontal_leg * vertical_leg)/2
  end

end

Classes and TDD - Test file

require 'rspec'
require_relative '../lib/geometry'


describe Square do

  let(:square) {Square.new(8)}

  it 'should take one argument - side' do
    expect(square.side).to eq(8)
  end
  it 'calculates the area' do
    expect(square.area).to eq(64)
  end
  it 'calculates the perimeter' do
    expect(square.perimeter).to eq(32)
  end
end

describe Circle do

  let(:circle) {Circle.new(8)}

  it 'should take one argument - radius' do
    expect(circle.radius).to eq(8)
  end
  it 'calculates diameter' do
    expect(circle.diameter).to eq(16)
  end
  it 'calculates circumference' do
    expect(circle.circumference).to eq(50.26548)
  end
  it 'calculates area' do
    expect(circle.area).to eq(201.06193)
  end
end

describe Rectangle do

  let(:rectangle) {Rectangle.new(6, 8)}

  it 'should take two arguments - length and width' do
    expect(rectangle.length).to eq(6)
    expect(rectangle.width).to eq(8)
  end
  it 'calculates area' do
    expect(rectangle.area).to eq(48)
  end
  it 'calculates perimeter' do
    expect(rectangle.perimeter).to eq(28)
  end
end

describe RightTriangle do

  let(:right_triangle) {RightTriangle.new(3, 4)}

  it 'should take two arguments - two sides' do
    expect(right_triangle.horizontal_leg).to eq(3)
    expect(right_triangle.vertical_leg).to eq(4)
  end
  it 'calculates length of hypotenuse' do
    expect(right_triangle.hypotenuse).to eq(5)
  end
  it 'calculates perimeter' do
    expect(right_triangle.perimeter).to eq(12)
  end
  it 'calculates area' do
    expect(right_triangle.area).to eq(6)
  end
end

Nice job Albert!

A couple of suggestions:

Test possible errors that could arise. For example, what happens if someone passes in a negative number, or 0, as the side to Square.new?

For floats, use RSpec's be_within matcher. Instead of having to round off your return values (e.g. for circle's area & circumference), you can use Rspec's be_within matcher to hardcode in some float that the return value should be close to.

If you do want to round a number, you can use the round method instead of the sprintf method & then convert back to the string. (See circle circumference and area methods.)