Midas.Assertions 1.0.4

Midas.Assertions

Zero-dependency fluent assertion library for .NET. Drop-in replacement for FluentAssertions with a familiar Should().Be() API.
Built by Midas Path Software Solutions — no commercial licensing, no telemetry, no surprises.

Why Midas.Assertions?

FluentAssertions introduced a commercial license requirement starting with v8. Rather than pay per-developer fees or freeze on an old version, we built our own — same fluent API, zero dependencies, MIT-licensed forever.

The result: 166 tests passing, covering the full assertion surface we actually use in production. If Should().Be() works in FluentAssertions, it works identically here.

Installation

dotnet add package Midas.Assertions

Quick Start

using Midas.Assertions;

// Object assertions
result.Should().NotBeNull();
result.Should().Be(expected);
result.Should().BeOfType<PatientDto>();

// String assertions
name.Should().NotBeNullOrWhiteSpace();
name.Should().StartWith("Dr.");
name.Should().Contain("Smith");
name.Should().MatchWildcard("Dr.*Smith*");

// Numeric assertions
age.Should().BeGreaterThan(0);
balance.Should().BeInRange(0, 1000);
temperature.Should().BeApproximately(98.6, 0.5);

// Boolean assertions
isActive.Should().BeTrue();
isDeleted.Should().BeFalse();

// DateTime assertions
createdAt.Should().BeBefore(DateTime.UtcNow);
expiresAt.Should().BeAfter(DateTime.UtcNow);
scheduledAt.Should().BeCloseTo(expected, TimeSpan.FromSeconds(1));

// Collection assertions
patients.Should().NotBeEmpty();
patients.Should().HaveCount(5);
patients.Should().Contain(p => p.Name == "Kwame");
callOrder.Should().ContainInOrder("save", "notify", "log");
tags.Should().OnlyHaveUniqueItems();

// Exception assertions (sync)
action.Should().Invoking(a => a.Execute())
    .Should().Throw<InvalidOperationException>()
    .WithMessage("*not allowed*");

// Exception assertions (async)
await func.Should().Invoking(f => f.ExecuteAsync())
    .Should().ThrowAsync<UnauthorizedAccessException>()
    .WithMessage("*expired*");

Assertion Classes

Fluent Chaining

All assertions return AndConstraint<T> so you can chain:

name.Should()
    .NotBeNull()
    .And.StartWith("Dr.")
    .And.HaveLength(expected.Length);

Exception assertions return ExceptionAssertions<T> for further checks:

act.Should().Throw<ArgumentException>()
    .WithMessage("*cannot be null*")
    .WithParameterName("patientId");

Cross-Numeric Comparisons

ObjectAssertions.Be() handles cross-numeric types automatically — uint.Should().Be(10) works even though uint and int are different types when boxed.

Migration from FluentAssertions

1. Replace using FluentAssertions; with using Midas.Assertions;
2. That's it. The API surface is the same.

Target Frameworks

• net8.0
• net9.0
• net10.0

License

MIT © Midas Path Software Solutions