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Update decimal rounding.
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@Corniel
Corniel committed Mar 28, 2024
1 parent f48fc47 commit a3ae76b
Showing 1 changed file with 70 additions and 69 deletions.
139 changes: 70 additions & 69 deletions .../Qowaiv.Specs/_Legacy/DecimalRoundTest.cs → specs/Qowaiv.Specs/Decimal_round_specs.cs
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@@ -1,62 +1,19 @@
namespace Qowaiv.UnitTests;
namespace Decimal_round_specs;

public class DecimalRoundTest
public class Rounds
{
[Test]
public void Round_RemainderZero_NoChange()
{
// initializes a decimal with scale of 4, instead of 0.
var value = decimal.Parse("1000.0000", CultureInfo.InvariantCulture);
var rounded = value.Round(-2);
rounded.Should().Be(1000m);
}

[Test]
public void Round_Positive_ShouldRoundToEven()
public void To_even_by_default_for_positive()
{
var rounded = 24.5m.Round();
rounded.Should().Be(24m);
}
[Test]
public void Round_Negative_ShouldRoundToEven()
{
var rounded = -24.5m.Round();
Assert.AreEqual(-24m, rounded);
}

[Test]
public void Round_ALotOf3s_WithoutIssues()
{
var value = 9_876_543_210m + 1m / 3m;
var rounded = value.Round(-9);
var expected = 10_000_000_000m;

rounded.Should().Be(expected);
}


[Test]
public void RoundToMultiple_PositiveWithMultipleOf_ShouldRoundToEven()
{
var rounded = 24.5m.RoundToMultiple(1m);
rounded.Should().Be(24m);
}
[Test]
public void RoundToMultiple_NegativeWithMultipleOf_ShouldRoundToEven()
public void To_even_by_default_for_negative()
{
var rounded = -26.5m.RoundToMultiple(1m);
Assert.AreEqual(-26m, rounded);
}


[TestCase(150.0, 125.0, 50, DecimalRounding.AwayFromZero)]
[TestCase(125.0, 123.0, 5, DecimalRounding.AwayFromZero)]
[TestCase(123.25, 123.3085, 0.25, DecimalRounding.AwayFromZero)]
[TestCase(666, 666, 3, DecimalRounding.AwayFromZero)]
public void Round_MultipleOf(decimal exp, decimal value, decimal factor, DecimalRounding mode)
{
var act = value.RoundToMultiple(factor, mode);
act.Should().Be(exp);
var rounded = -24.5m.Round();
rounded.Should().Be(-24m);
}

/// <remarks>Use strings as doubles lack precision.</remarks>
Expand All @@ -80,7 +37,7 @@ public void Round_MultipleOf(decimal exp, decimal value, decimal factor, Decimal
[TestCase("120000000", -7)]
[TestCase("100000000", -8)]
[TestCase(0, -9)]
public void Round_Digits(decimal exp, int digits)
public void Takes_digits_into_account(decimal exp, int digits)
{
var act = 123456789.123456789m.Round(digits, DecimalRounding.AwayFromZero);
act.Should().Be(exp);
Expand Down Expand Up @@ -110,50 +67,94 @@ public void Round_Digits(decimal exp, int digits)
[TestCase(+25, +25.1, DecimalRounding.Floor)]
[TestCase(-25, -25.1, DecimalRounding.Truncate)]
[TestCase(+25, +25.1, DecimalRounding.Truncate)]
public void Round_NearestAndDirect(decimal exp, decimal value, DecimalRounding mode)
public void Takes_strategy_into_account(decimal rounded, decimal value, DecimalRounding mode)
{
var act = value.Round(0, mode);
act.Should().Be(exp);
act.Should().Be(rounded);
}

[Test]
public void Round_RandomTieBreaking()
[TestCase(17.1)]
[TestCase(17.3)]
[TestCase(17.6)]
[TestCase(17.8)]
public void Stochastic_within_margin(decimal value)
{
var value = 17.5m;

var runs = 100_000;
var runs = 10_000;
var sum = 0m;

for(var i = 0; i < runs; i++)
for (var i = 0; i < runs; i++)
{
var rounded = value.Round(0, DecimalRounding.RandomTieBreaking);
var rounded = value.Round(0, DecimalRounding.StochasticRounding);
(rounded == 17 || rounded == 18).Should().BeTrue();
sum += rounded;
}

var avg = sum / runs;

Assert.That(avg, Is.EqualTo(value).Within(0.05m));
avg.Should().BeApproximately(value, 0.05m);
}

[TestCase(17.1)]
[TestCase(17.3)]
[TestCase(17.6)]
[TestCase(17.8)]
public void Round_StochasticRounding(decimal value)
[Test]
public void Tie_breaking_within_margin()
{
var runs = 10_000;
var value = 17.5m;

var runs = 100_000;
var sum = 0m;

for (var i = 0; i < runs; i++)
{
var rounded = value.Round(0, DecimalRounding.StochasticRounding);
var rounded = value.Round(0, DecimalRounding.RandomTieBreaking);
(rounded == 17 || rounded == 18).Should().BeTrue();
sum += rounded;
}

var avg = sum / runs;
avg.Should().BeApproximately(value, 0.05m);
}

Assert.That(avg, Is.EqualTo(value).Within(0.05m));
[Test]
public void Supports_non_leading_decimal_zeros()
{
// initializes a decimal with scale of 4, instead of 0.
var value = decimal.Parse("1000.0000", CultureInfo.InvariantCulture);
var rounded = value.Round(-2);
rounded.Should().Be(1000m);
}

[Test]
public void Round_ALotOf3s_WithoutIssues()
{
var value = 9_876_543_210m + 1m / 3m;
var rounded = value.Round(-9);
var expected = 10_000_000_000m;

rounded.Should().Be(expected);
}
}

public class Rounds_to_multiple
{
[Test]
public void To_even_by_default_for_positive()
{
var rounded = 24.5m.RoundToMultiple(1m);
rounded.Should().Be(24m);
}

[Test]
public void To_even_by_default_for_negative()
{
var rounded = -26.5m.RoundToMultiple(1m);
rounded.Should().Be(-26m);
}

[TestCase(150.0, 125.0, 50, DecimalRounding.AwayFromZero)]
[TestCase(125.0, 123.0, 5, DecimalRounding.AwayFromZero)]
[TestCase(123.25, 123.3085, 0.25, DecimalRounding.AwayFromZero)]
[TestCase(666, 666, 3, DecimalRounding.AwayFromZero)]
public void Supports_rouding_stratgies(decimal rounded, decimal value, decimal factor, DecimalRounding mode)
{
var act = value.RoundToMultiple(factor, mode);
act.Should().Be(rounded);
}
}

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