Seed a Specific Failing Case for Reproduction¶

Problem¶

A composed test failed — in CI, or on a teammate's machine — and you need the exact composed values that produced it, not a plausible-looking re-creation.

Solution¶

A composition failure's own message always ends with the seed that produced it:

Compono.CompositionException : No provider could satisfy IShippingCalculator.

Order -> IShippingCalculator

Seed: 24601

Paste that value straight into [Compose(Seed = ...)]:

[Theory]
[Compose(Seed = 24601)]
public void ReproducesTheReportedFailure(Order order) { }

Running this reproduces the identical composed row that failed originally — same values, same failure, every time.

Discussion¶

For programmatic composition (no Compono.XunitV3 theory involved), the seed lives on the caught CompositionException's Diagnostic property instead of the message text directly:

try
{
    composer.Create<Order>();
}
catch (CompositionException exception)
{
    Console.WriteLine(exception.Diagnostic); // ... Seed: 24601
}

Reuse it with Composer.Create(builder => builder.WithSeed(24601)) — the programmatic equivalent of [Compose(Seed = ...)]. The two seed paths (row-scoped vs. programmatic) are independent derivations, not interchangeable with each other — reproduce a [Compose] failure with [Compose(Seed = ...)], and a programmatic one with WithSeed(...).

Seed a Specific Failing Case for Reproduction¶

Problem¶

Solution¶

Discussion¶

See also¶