# Starter file for tests for Assignment 8 (trees and symbolic differentiation)
# There should be enough tests here for symbolic differentiation -- you
# should add another class TestTree for unit tests for the tree classes.

require 'test/unit'
require 'assign8'

# put definition here for tree tests:
# class TestTree < Test::Unit::TestCase


class TestDeriv < Test::Unit::TestCase

  def test_simplify
    x = Variable.new("x")
    assert_equal(10, (0*(x+3)+10).simplify)
    assert_equal(3.5, (0*(x+2.8)+3.5).simplify)
  end

  def test_to_s
    x = Variable.new("x")
    assert_equal("x", x.to_s)
    # these tests assume that you turn expressions into fully-parenthesized
    # strings -- change these if you remove unneeded parentheses
    assert_equal("(3*(10+x))", (3*(10+x)).to_s)
    assert_equal("((10*x)+3)", (10*x+3).to_s)
  end

  def test_const_and_var
    x = Variable.new("x")
    y = Variable.new("y")
    assert_equal(0, 3.deriv(x))
    assert_equal(1, x.deriv(x))
    assert_equal(0, y.deriv(x))
  end

  def test_plus
    x = Variable.new("x")
    y = Variable.new("y")
    assert_equal(1, (x+y).deriv(x))
    assert_equal(1, (x+3).deriv(x))
    assert_equal(1, (3+x).deriv(x))
  end

  def test_times
    x = Variable.new("x")
    y = Variable.new("y")
    assert_equal(y, (x*y).deriv(x))
    assert_equal(3, (x*3).deriv(x))
    assert_equal(3, (3*x).deriv(x))
    assert_equal(2.8, (x*2.8).deriv(x))
  end

  def test_complicated
    x = Variable.new("x")
    y = Variable.new("y")
    assert_equal(x*y+(x+3)*y, (x*y*(x+3)).deriv(x))
    assert_equal(50, (10*(2*x+3*x+5)).deriv(x))
    assert_equal(57.2, (10*(2.52*x+3.2*x+5.99)).deriv(x))
  end

  def test_unary
    # test unary + and -
    x = Variable.new("x")
    assert_equal(-1*x, -x)
    assert_equal(x, +x)
  end

  # change the name to test_trig to enable this test (if you do the 
  # extra credit question)
  def skip_test_trig
    x = Variable.new("x")
    y = Variable.new("y")
    assert_equal(x.cos, x.sin.deriv(x))
    assert_equal(-x.sin, x.cos.deriv(x))
  end

end