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Sort order

Describes how to verify that the items of a collection are sorted.

ExpectationNegatedSummary
IsInAscendingOrderIsNotInAscendingOrderthe items are sorted ascending
IsInDescendingOrderIsNotInDescendingOrderthe items are sorted descending

Ascending / descending​

You can verify that a collection is (or is not) sorted in ascending or descending order:

IEnumerable<int> trackNumbers = [1, 2, 3];
IEnumerable<int> shuffledTrackNumbers = [1, 3, 2];

await That(trackNumbers).IsInAscendingOrder();
await That(shuffledTrackNumbers).IsNotInAscendingOrder();
await That(["Let It Be", "Help!", "Abbey Road"]).IsInDescendingOrder();
await That(["Help!", "Abbey Road", "Let It Be"]).IsNotInDescendingOrder();

You can also specify a custom comparer:

await That(["abbey road", "Help!", "let it be"]).IsInAscendingOrder()
  .Using(StringComparer.OrdinalIgnoreCase);

For objects, you can also verify the sort order on a member:

Album[] albums = //...

await That(albums).IsInAscendingOrder(x => x.Title);

Strings are compared ordinally by default, also in an untyped collection. A SortedSet<T> or ImmutableSortedSet<T>, and the keys of a sorted dictionary, are ordered by their own comparer, unless a comparer or a member is specified.

Mixed DateTimeKind values

A DateTime sequence that mixes Utc and Local values fails, also when negated, unless a custom comparer is used. The order of Utc and Local values depends on the time zone, so such a sequence fails the check in both forms. This also applies to a DateTime member and to an untyped collection. Values with DateTimeKind.Unspecified are compatible with both kinds.