MathAssertions.TUnit 0.0.1

MathAssertions.TUnit

Scope: Test projects only. Not intended for production code.

TUnit-native fluent math-assertion DSL for System.Numerics compound types and BCL floating-point primitives. NaN-aware, infinity-aware, AOT-compatible, no runtime reflection in the assertion path.

Full documentation, "Why component-wise rather than Euclidean", cookbook, design notes, and roadmap: github.com/JohnVerheij/MathAssertions.TUnit

Status: v0.0.1 (initial preview)

This first release is a deliberately narrow skeleton. v0.0.1 ships a single fluent entry point: Vector3.IsApproximatelyEqualTo(expected, tolerance). The wider System.Numerics catalog plus statistics, linear-algebra invariants, number theory, and 3D-geometry surface land at v0.1.0.

Install

dotnet add package MathAssertions.TUnit

MathAssertions (the framework-agnostic core) comes transitively. Requirements: TUnit 1.43.11 or later, .NET 10.

The source-generated entry point (IsApproximatelyEqualTo on Vector3) auto-imports via TUnit.Assertions.Extensions. The only additional using you typically need is System.Numerics for the value type itself. If you call MathTolerance.IsApproximatelyEqual directly from a [GenerateAssertion] extension on a private domain type, add MathAssertions to your GlobalUsings.cs:

global using MathAssertions;

Quick start

using System.Numerics;

[Test]
public async Task ComputedPositionIsApproximatelyAtTarget(CancellationToken ct)
{
    Vector3 target = new(0.300f, 0.150f, 0.450f);
    Vector3 actual = SolveTrajectory(input);

    await Assert.That(actual).IsApproximatelyEqualTo(target, tolerance: 1e-3);
}

Entry points (v0.0.1)

The wider catalog (Vector2/4, Quaternion + rotational equivalence, Matrix4x4, Plane + geometric equivalence, Complex, double[]/float[], spans) lands at v0.1.0 alongside additional method families (statistics, linear-algebra invariants, number theory, 3D geometry).

Extending to your own types

Add tolerance assertions for your own domain types via a one-line [GenerateAssertion] extension calling MathTolerance.IsApproximatelyEqual on each component. The package never sees your private types.

using MathAssertions;
using TUnit.Assertions.Attributes;

file static class PositionAssertions
{
    [GenerateAssertion(
        ExpectationMessage = "to be approximately equal to {expected} within tolerance {tolerance}",
        InlineMethodBody = true)]
    public static bool IsApproximatelyEqualTo(this MyPosition value, MyPosition expected, double tolerance)
        => MathTolerance.IsApproximatelyEqual(value.AsVector3(), expected.AsVector3(), tolerance);
}

Failure diagnostics

On a failed assertion, the exception message renders the actual Vector3 against the expected and the supplied tolerance:

Expected:
  to be approximately equal to <1, 2, 99> component-wise within tolerance 0.001

Actual:
  <1, 2, 3>

Full failure-diagnostics examples, design notes, stability intent, and roadmap on GitHub.

Family

Part of an assertion family for TUnit:

• LogAssertions.TUnit
• SnapshotAssertions.TUnit
• TimeAssertions.TUnit

License

MIT. Copyright (c) 2026 John Verheij.