public void Max_Throws_If_Argument_Is_Null()
{
var source = Enumerable.Empty <Foo>();
var comparer = XComparer.By(_getFooValue);
// ReSharper disable once ReturnValueOfPureMethodIsNotUsed
TestHelper.AssertThrowsWhenArgumentNull(() => source.Max(comparer));
}
public void Min_Throws_If_Source_Is_Null()
{
IEnumerable <Foo> source = null;
var comparer = XComparer.By(_getFooValue);
// ReSharper disable once AssignNullToNotNullAttribute
// ReSharper disable once ReturnValueOfPureMethodIsNotUsed
var ex = Assert.Throws <ArgumentNullException>(() => source.Min(comparer));
ex.ParamName.Should().Be("source");
}
public void By_Returns_A_Comparer_Based_On_Key()
{
var a = new Foo {
X = 0, Y = 0
};
var b = new Foo {
X = 1, Y = 0
};
Func <Foo, int> keySelector = f => f.X;
var comparer = XComparer.By(keySelector);
int expected = -1;
int actual = comparer.Compare(a, b);
Assert.AreEqual(expected, actual);
}
public void ThenByDescending_Returns_A_Comparer_Based_On_First_Then_Descending_Second_Key()
{
var a = new Foo {
X = 0, Y = 0
};
var b = new Foo {
X = 0, Y = 1
};
Func <Foo, int> keySelector1 = f => f.X;
Func <Foo, int> keySelector2 = f => f.Y;
var comparer = XComparer.By(keySelector1).ThenByDescending(keySelector2);
int expected = 1;
int actual = comparer.Compare(a, b);
Assert.AreEqual(expected, actual);
}
public void ChainWith_Uses_Next_Comparer_If_First_Returns_Zero()
{
var a = new Foo {
X = 0, Y = 0
};
var b = new Foo {
X = 0, Y = 1
};
var first = XComparer <Foo> .By(f => f.X);
var next = Intercept(XComparer <Foo> .By(f => f.Y));
var comparer = first.ChainWith(next);
int expected = -1;
int actual = comparer.Compare(a, b);
Assert.AreEqual(expected, actual);
Assert.AreEqual(1, next.CallCount);
}
public void RankBy_Uses_Specified_Key_Comparer()
{
var source = new[]
{
new Player("Alice", -42),
new Player("Bob", -25),
new Player("Charlie", 75),
new Player("David", -17),
new Player("Emily", 31)
}.ForbidMultipleEnumeration();
var keyComparer = XComparer <int> .By(Math.Abs);
var result = source.RankBy(p => p.Score, (player, rank) => $"{rank}. {player.Name}", keyComparer);
result.Should().Equal(
"1. David",
"2. Bob",
"3. Emily",
"4. Alice",
"5. Charlie");
}
public void Chaining_Multiple_Comparers_Works_As_Well()
{
var a = new Foo {
X = 0, Y = 0, Z = 1
};
var b = new Foo {
X = 0, Y = 0, Z = 0
};
var first = XComparer <Foo> .By(f => f.X);
var second = XComparer <Foo> .By(f => f.Y);
var third = XComparer <Foo> .By(f => f.Z);
// Test various ways of chaining
// (first.second).third
var comparer = first.ChainWith(second).ChainWith(third);
int expected = 1;
int actual = comparer.Compare(a, b);
Assert.AreEqual(expected, actual);
// first.(second.third)
comparer = first.ChainWith(second.ChainWith(third));
expected = 1;
actual = comparer.Compare(a, b);
Assert.AreEqual(expected, actual);
// (first.second).(first.second)
comparer = first.ChainWith(second).ChainWith(first.ChainWith(second));
expected = 0;
actual = comparer.Compare(a, b);
Assert.AreEqual(expected, actual);
}
public static IComparer <T> By <TKey>(
[NotNull] Func <T, TKey> keySelector,
IComparer <TKey>?keyComparer = null)
{
return(XComparer.By(keySelector, keyComparer));
}