JustDummies.Xunit 1.0.0-preview.1

JustDummies.Xunit

The xUnit v3 companion of JustDummies. Mark a test [Reproducible] and its arbitrary values are drawn from a pinned seed — reported only when the test fails, so a red test names the exact seed to replay while a green one stays silent.

Why

JustDummies makes a run reproducible by wrapping the test body in a delegate:

[Fact]
public void Order_reference_is_accepted() {
    Any.Reproducibly(() => {
        string reference = Any.String().StartingWith("ORD-").WithLength(12).Generate();
        // ... act, assert ...
    });
}

That works on every test framework, and stays the portable form. This package removes the ceremony for xUnit v3:

[Fact, Reproducible]
public void Order_reference_is_accepted() {
    string reference = Any.String().StartingWith("ORD-").WithLength(12).Generate();
    // ... act, assert ...
}

Values still vary between runs — which is what surfaces a test secretly depending on one — but a failure is now recoverable even though the body was never wrapped in advance.

Replaying a failure

A failing test writes its seed to the test output:

[JustDummies] These arbitrary values were seeded with 1234. Reproduce this run with [Reproducible(Seed = 1234)].

Pin it to replay:

[Fact, Reproducible(Seed = 1234)]
public void Order_reference_is_accepted() { /* ... */ }

The same snippet is what a generation failure names, so a diagnostic never points at a call the test does not contain.

Where it applies

• A test: [Fact, Reproducible] or [Theory, Reproducible].
• A class: [Reproducible] on the class covers every test it declares.
• A whole suite: [assembly: Reproducible].

The hooks run once per test case, so each case of a theory draws its own seed rather than sharing one with its siblings. When several levels apply, the most specific one wins for the duration of the test and the outer ones are restored after it — an assembly-wide [Reproducible] can pin the suite while one test replays a particular seed.

Notes

• Values drawn from an explicit Any.WithSeed(...) context are unaffected: that context is isolated by design and does not draw from the ambient source this attribute pins.
• The seed is pinned through Any.UseSeed(...), a public handle any test-framework adapter can use — this package holds no privileged access to JustDummies.
• xUnit v3 only. On xUnit v2, NUnit, MSTest or anything else, use Any.Reproducibly(...): it is unaffected by this package and works everywhere.

Links

• Repository
• JustDummies

Credits

The package icon is a crash-test dummy by Magnific, from Flaticon.