# unit tests for the symbolic differentiation program in Ruby This
# includes commented-out unit tests for the extra credit question for
# exponentiation, sin, and cos -- uncomment those if you do the extra credit.

require 'test/unit'
require 'assign8'

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)
    # extra credit part follows
    # assert_equal(0, 0.sin.simplify)
    # assert_equal(1, 0.cos.simplify)
    # assert_equal(1000, (10**3).simplify)
    # assert_equal(1, (x**0).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_minus
    x = Variable.new("x")
    y = Variable.new("y")
    assert_equal(1, (x-y-3).deriv(x))
    assert_equal(-1, (x-y).deriv(y))
    assert_equal(-1, (-x).deriv(x))
    assert_equal(3, (-y+3*x-5).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(0-x, -x)
    assert_equal(x, +x)
  end

#   def 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))
#     # you may need to reorder the expressions for the derivative
#     # depending on how your deriv method is defined
#     assert_equal((4*x).cos*4, (4*x).sin.deriv(x))
#     assert_equal((-(4*x).sin)*4, (4*x).cos.deriv(x))
#   end

#   def test_expt
#     x = Variable.new("x")
#     y = Variable.new("y")
#     assert_equal(2*x, (x**2).deriv(x))
#     assert_equal(1, (x**1).deriv(x))
#     # similarly you may need to reorder the expressions for the derivative
#     # depending on how your deriv method is defined
#     assert_equal(4*x**3, (x**4).deriv(x))
#     assert_equal(4*(3*x*y)**3 * (y*3), ((3*x*y)**4).deriv(x))
#   end

end