Struct Settings 

pub struct Settings { /* private fields */ }

Configuration for a Hegel test run.

Use builder methods to customize, then pass to [Hegel::settings] or the settings parameter of #[hegel::test].

In CI environments (detected automatically), the database is disabled and tests are derandomized by default.

Implementations

impl Settings

pub fn new() -> Self

Create settings with defaults. Detects CI environments automatically.

pub fn mode(self, mode: Mode) -> Self

Set the execution mode. Defaults to Mode::TestRun.

pub fn backend(self, backend: Backend) -> Self

Select the randomness backend.

By default the backend is chosen automatically: Backend::Urandom when running inside Antithesis, and Backend::Default otherwise. Calling this pins the choice, overriding the automatic detection.

pub fn test_cases(self, n: u64) -> Self

Set the number of test cases to run (default: 100).

pub fn verbosity(self, verbosity: Verbosity) -> Self

Set the verbosity level.

pub fn seed(self, seed: Option<u64>) -> Self

Set a fixed seed for reproducibility, or None for random.

pub fn derandomize(self, derandomize: bool) -> Self

When true, use a fixed seed derived from the test name. Enabled by default in CI.

pub fn database(self, database: Option<String>) -> Self

Set the database path for storing failing examples, or None to disable.

pub fn phases(self, phases: impl IntoIterator<Item = Phase>) -> Self

Set which test lifecycle phases to run.

Defaults to all phases: [Phase::Explicit, Phase::Reuse, Phase::Generate, Phase::Target, Phase::Shrink].

Example — skip shrinking (useful when you only need a witness, not a minimal counterexample):

use hegel::{Phase, Settings};

let s = Settings::new().phases([Phase::Reuse, Phase::Generate]);

pub fn print_blob(self, print_blob: bool) -> Self

Print a copy-pasteable #[hegel::reproduce_failure("…")] line for the counterexample when a test fails. Defaults to false.

The reproduce blob is always attached to the failure. This setting only controls whether it is printed to the failure output. Has effect only on the native backend.

pub fn suppress_health_check( self, checks: impl IntoIterator<Item = HealthCheck>, ) -> Self

Suppress one or more health checks so they do not cause test failure.

Health checks detect common issues like excessive filtering or slow tests. Use this to suppress specific checks when they are expected. Replaces any previously configured suppressions, like Settings::phases.

Example

use hegel::{HealthCheck, Verbosity};
use hegel::generators as gs;

#[hegel::test(suppress_health_check = [HealthCheck::FilterTooMuch, HealthCheck::TooSlow])]
fn my_test(tc: hegel::TestCase) {
    let n: i32 = tc.draw(gs::integers());
    tc.assume(n > 0);
}

pub fn has_phase(&self, phase: Phase) -> bool

Returns true if the given phase is enabled in these settings.

pub fn report_multiple_failures(self, report_multiple_failures: bool) -> Self

Control whether multi-bug runs report every distinct failing example or collapse to just the first one.

When true (the default), each distinct origin Hegel finds is surfaced as its own diagnostic, and the final panic message reports the count of distinct failures. Setting this to false makes Hegel collapse a multi-bug run to one example — useful when you have a flaky predicate that triggers several superficially-distinct failures whose root cause is the same, and the extra reports are just noise.

Maps to Hypothesis’s report_multiple_bugs setting.

Trait Implementations

impl Clone for Settings

fn clone(&self) -> Settings

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Settings

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Settings

fn default() -> Self

Returns the “default value” for a type.