OmniAssert 2.3.0

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OmniAssert is a fluent assertion library for .NET 10 and C# 14. Tests read like plain English and failures show the expression under test, actual values, and optional compile-time operand capture.

Built with substantial AI assistance. Review the implementation before use in security-sensitive or compliance-heavy environments.

Documentation

Full documentation — API reference, soft assertions, object diffing, interceptors, analyzer rules (OA001–OA007), v1 → v2 migration, and Extensions.

Key features

• Fluent API — user.Email.Must().Contain("@") reads naturally across strings, numbers, collections, objects, exceptions, files, dates, spans, and nullable values
• Deep object comparison — BeEquivalentTo compares object graphs recursively with hierarchical diffs
• Soft assertions — AssertionScope collects multiple failures and reports them together
• Compile-time diagnostics — optional Roslyn interceptors capture operand values when boolean expressions fail

Quick start

<ItemGroup>
  <PackageReference Include="OmniAssert" Version="2.3.0" />
  
  <PackageReference Include="OmniAssert.Extensions" Version="2.3.0" />
</ItemGroup>

using OmniAssert;
using OmniAssert.Extensions.Web; // when using Extensions

user.Id.Must().BeGreaterThan(0);
user.Email.Must().BeEmailAddress();
(() => Service.Create(badInput)).Throws<ArgumentException>();

Recently added assertions

Convenience assertions added on top of the core primitives:

Strings — BeTrimmed(), HaveLengthBetween(min, max), BeAlphanumeric(), BeLowerCase(), BeUpperCase(), BeNumeric(), BeBase64(), BeHexString(), BeHexColor(), BeIso8601(), BeDateString(format), BeAbsolutePath(), BeRelativePath(). String date/format validators parse with CultureInfo.InvariantCulture so they are culture-independent.

Numbers — BePositive(), BeNegative(), BeEven(), BeOdd(), BeMultipleOf(n), BeFinite(), BeInfinite(), HaveDecimalPlaces(n).

Dates — DateTime/DateTimeOffset: BeInPast(), BeInFuture(), BeSameDayAs(expected). DateOnly: BeToday(), BeYesterday(), BeTomorrow(), BeWeekday(), BeWeekend(), BeLeapYear(), BeWithinDays(n, anchor). BeInPast/BeInFuture compare against UtcNow, so subjects should be UTC; the DateOnly "today" helpers use the local clock and can shift across midnight.

Collections — HaveCountBetween(min, max) (also on spans), ContainOnly(allowed), ContainOnly(predicate), BeSubsetOf(expected), BeSupersetOf(expected). Set operations use default equality with set semantics.

Files — NotBeEmpty(), HaveExtension(ext) (leading dot optional, case-insensitive).

Equivalence options — BeEquivalentTo(expected, EquivalenceOptions) on collections and objects, with IgnoreCase and IgnoreCollectionOrder flags.

order.Total.Must().BePositive();
sku.Must().BeAlphanumeric();
createdAt.Must().BeInPast();
roles.Must().BeSubsetOf(allRoles);
actual.Must().BeEquivalentTo(expected, new EquivalenceOptions { IgnoreCase = true, IgnoreCollectionOrder = true });

Suggested name → OmniAssert equivalent

Common assertion names from other libraries and their OmniAssert spelling:

Contributing

See CONTRIBUTING.md.

License

GNU General Public License v3.0 — see LICENSE.