public Property AssociativeLaw(int x, int y, int z)
{
// (x * y) * z = x * (y * z)
var sut = new RussianPeasantMultiplier();
return((sut.Multiply(sut.Multiply(x, y), z) == sut.Multiply(x, sut.Multiply(y, z))).ToProperty());
}
public Property DistributiveLaw(int x, int y, int z)
{
// x * (y + z) = (x * y) + (x * z)
var sut = new RussianPeasantMultiplier();
return((sut.Multiply(x, y + z) == sut.Multiply(x, y) + sut.Multiply(x, z)).ToProperty());
}
public Property CommutativeLaw(int x, int y)
{
// x * y = y * x
var sut = new RussianPeasantMultiplier();
return((sut.Multiply(x, y) == sut.Multiply(y, x)).ToProperty());
}
public Property NegationLaw(int x)
{
// -1 * x = -x where -1 * -1 = 1
var sut = new RussianPeasantMultiplier();
sut.Multiply(-1, -1).Should().Equals(1);
return((sut.Multiply(-1, x) == -x).ToProperty());
}
public Property NegativeOrderPreservationLaw(int x, int y, int z)
{
// Forall x < 0, if y > z then x * y < x * z
var sut = new RussianPeasantMultiplier();
var lhs = sut.Multiply(x, y);
var rhs = sut.Multiply(x, z);
Func <bool> property = () => lhs < rhs;
return(property.When(x < 0 && y > z));
}
public void When_logging_of_steps_enabled()
{
var sut = new RussianPeasantMultiplier(true);
Assert.Equal(12 * 45, sut.Multiply(12, 45));
Assert.Equal(4, sut.Steps.Count);
}
public void When_logging_of_steps_enabled()
{
var sut = new RussianPeasantMultiplier(true);
sut.Multiply(12, 45).Should().Equals(12 * 45);
sut.Steps.Count.Should().Equals(4);
}
public void When_logging_of_steps_disabled()
{
var sut = new RussianPeasantMultiplier(false);
Assert.Equal(67 * 42, sut.Multiply(67, 42));
Assert.Equal(0, sut.Steps.Count);
}
public void When_logging_of_steps_disabled()
{
var sut = new RussianPeasantMultiplier(false);
sut.Multiply(67, 42).Should().Equals(67 * 42);
sut.Steps.Count.Should().Equals(0);
}
public void When_x1_is_negative()
{
var sut = new RussianPeasantMultiplier();
var product = sut.Multiply(-23, 45);
product.Should().Equals(-23 * 45);
product.Should().BeNegative();
}
public void When_both_values_are_negative()
{
var sut = new RussianPeasantMultiplier();
var product = sut.Multiply(-42, -68);
product.Should().Equals(42 * 68);
product.Should().BePositive();
}
public void When_x1_is_negative()
{
var sut = new RussianPeasantMultiplier();
var product = sut.Multiply(-23, 45);
Assert.Equal(-23 * 45, product);
Assert.True(product < 0);
}
public void When_both_values_are_negative()
{
var sut = new RussianPeasantMultiplier();
var product = sut.Multiply(-42, -68);
Assert.Equal(42 * 68, product);
Assert.True(product > 0);
}
public Property ZeroLaw(int x)
{
// Zero is the absorbing element for multiplication - as opposed to addition which does not have an absorbing element
// https://en.wikipedia.org/wiki/Absorbing_element
// 0 * x = 0
// x * 0 = 0 //Right zero also proven if commutative property holds
var sut = new RussianPeasantMultiplier();
return((sut.Multiply(0, x) == 0).ToProperty());
}
public Property IdentityLaw(int x)
{
// 1 * x = x
// x * 1 = x // right identity is also proven if commutative property holds
// -1 * x = -x // left negative identity also proven if negation property holds
// x * -1 = -x // right negative identity also proven if cummutative and negation holds
var sut = new RussianPeasantMultiplier();
return((sut.Multiply(1, x) == x).ToProperty());
}
public void When_absolute_value_of_negative_x1_is_greater_than_x2()
{
var sut = new RussianPeasantMultiplier();
const int x1 = -65;
const int x2 = 35;
sut.Multiply(x1, x2).Should().Equals(-65 * 35);
sut.X1.Should().Equals(x2); //Assert arguments swapped
sut.X2.Should().Equals(x1);
}
public void When_absolute_value_of_negative_x1_is_greater_than_x2()
{
var sut = new RussianPeasantMultiplier();
const int x1 = -65;
const int x2 = 35;
Assert.Equal(-65 * 35, sut.Multiply(x1, x2));
Assert.Equal(x2, sut.X1); //Assert arguments swapped
Assert.Equal(x1, sut.X2);
}
public void When_multiplying_1_and_x()
{
//Arrange
var sut = new RussianPeasantMultiplier();
//Act
var product = sut.Multiply(1, 2);
//Assert
Assert.Equal(2, product);
}
private static bool DoTheMultiplication(bool showSteps)
{
var x1 = GetValue("first value");
var x2 = GetValue("second value");
Console.WriteLine("Multiplying {0} and {1} using Russian peasant multiplication", x1, x2);
var result = russianPeasantMultiplier.Multiply(x1, x2);
if (showSteps)
{
ShowSteps(russianPeasantMultiplier.Steps);
}
Console.WriteLine("Result: {0}", result);
return(GetYesNo("Do another multiplication? (y/n) "));
}
public void When_multiplying_two_large_numbers()
{
var sut = new RussianPeasantMultiplier();
Assert.Equal(465 * 23, sut.Multiply(465, 23));
}
public void When_x1_is_larger_than_x2()
{
var sut = new RussianPeasantMultiplier();
sut.Multiply(52, 35).Should().Equals(52 * 35);
}
public void When_x1_is_smaller_than_x2()
{
var sut = new RussianPeasantMultiplier();
Assert.Equal(52 * 35, sut.Multiply(35, 52));
}
public void When_x1_is_larger_than_x2()
{
var sut = new RussianPeasantMultiplier();
Assert.Equal(52 * 35, sut.Multiply(52, 35));
}
public void When_multiplying_2_and_x()
{
var sut = new RussianPeasantMultiplier();
sut.Multiply(2, 5).Should().Equals(5 + 5);
}
public void When_x1_and_x2_is_0()
{
var sut = new RussianPeasantMultiplier();
sut.Multiply(0, 0).Should().Equals(0);
}
public void When_multiplying_x_and_2()
{
var sut = new RussianPeasantMultiplier();
sut.Multiply(7, 2).Should().Equals(7 + 7);
}
public void When_multiplying_two_large_numbers()
{
var sut = new RussianPeasantMultiplier();
sut.Multiply(465, 23).Should().Equals(465 * 23);
}
public void When_multiplying_x_and_2()
{
var sut = new RussianPeasantMultiplier();
Assert.Equal(7 + 7, sut.Multiply(7, 2));
}
public void When_multiplying_1_and_x()
{
var sut = new RussianPeasantMultiplier();
sut.Multiply(1, 2).Should().Equals(2);
}
public void When_x1_is_smaller_than_x2()
{
var sut = new RussianPeasantMultiplier();
sut.Multiply(35, 52).Should().Equals(52 * 35);
}