Struct Config

Fields

cases: u32

The number of successful test cases that must execute for the test as a whole to pass.

This does not include implicitly-replayed persisted failing cases.

The default is 256, which can be overridden by setting the PROPTEST_CASES environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

max_local_rejects: u32

The maximum number of individual inputs that may be rejected before the test as a whole aborts.

The default is 65536, which can be overridden by setting the PROPTEST_MAX_LOCAL_REJECTS environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

max_global_rejects: u32

The maximum number of combined inputs that may be rejected before the test as a whole aborts.

The default is 1024, which can be overridden by setting the PROPTEST_MAX_GLOBAL_REJECTS environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

max_flat_map_regens: u32

The maximum number of times all Flatten combinators will attempt to regenerate values. This puts a limit on the worst-case exponential explosion that can happen with nested Flattens.

The default is 1_000_000, which can be overridden by setting the PROPTEST_MAX_FLAT_MAP_REGENS environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

failure_persistence: Option<Box<dyn FailurePersistence>>

Indicates whether and how to persist failed test results.

When compiling with "std" feature (i.e. the standard library is available), the default is Some(Box::new(FileFailurePersistence::SourceParallel("proptest-regressions"))).

Without the standard library, the default is None, and no persistence occurs.

See the docs of FileFailurePersistence and MapFailurePersistence for more information.

You can disable failure persistence with the PROPTEST_DISABLE_FAILURE_PERSISTENCE environment variable but its not currently possible to set the persistence file with an environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

source_file: Option<&'static str>

File location of the current test, relevant for persistence and debugging.

Note the use of &str rather than Path to be compatible with #![no_std] use cases where Path is unavailable.

See the docs of FileFailurePersistence for more information on how it may be used for persistence.

test_name: Option<&'static str>

The fully-qualified name of the test being run, as would be passed to the test executable to run just that test.

This must be set if fork is true. Otherwise, it is unused. It is automatically set by proptest!.

This must include the crate name at the beginning, as produced by module_path!().

fork: bool

If true, tests are run in a subprocess.

Forking allows proptest to work with tests which may fail by aborting the process, causing a segmentation fault, etc, but can be a lot slower in certain environments or when running a very large number of tests.

For forking to work correctly, both the Strategy and the content of the test case itself must be deterministic.

This requires the "fork" feature, enabled by default.

The default is false, which can be overridden by setting the PROPTEST_FORK environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

timeout: u32

If non-zero, tests are run in a subprocess and each generated case fails if it takes longer than this number of milliseconds.

This implicitly enables forking, even if the fork field is false.

The type here is plain u32 (rather than Option<std::time::Duration>) for the sake of ergonomics.

This requires the "timeout" feature, enabled by default.

Setting a timeout to less than the time it takes the process to start up and initialise the first test case will cause the whole test to be aborted.

The default is 0 (i.e., no timeout), which can be overridden by setting the PROPTEST_TIMEOUT environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

max_shrink_time: u32

If non-zero, give up the shrinking process after this many milliseconds have elapsed since the start of the shrinking process.

This will not cause currently running test cases to be interrupted.

This configuration is only available when the std feature is enabled (which it is by default).

The default is 0 (i.e., no limit), which can be overridden by setting the PROPTEST_MAX_SHRINK_TIME environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

max_shrink_iters: u32

Give up on shrinking if more than this number of iterations of the test code are run.

Setting this to std::u32::MAX causes the actual limit to be four times the number of test cases.

Setting this value to 0 disables shrinking altogether.

Note that the type of this field will change in a future version of proptest to better accommodate its special values.

The default is std::u32::MAX, which can be overridden by setting the PROPTEST_MAX_SHRINK_ITERS environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

max_default_size_range: usize

The default maximum size to proptest::collection::SizeRange. The default strategy for collections (like Vec) use collections in the range of 0..max_default_size_range.

The default is 100 which can be overridden by setting the PROPTEST_MAX_DEFAULT_SIZE_RANGE environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

result_cache: fn() -> Box<dyn ResultCache>

A function to create new result caches.

The default is to do no caching. The easiest way to enable caching is to set this field to basic_result_cache (though that is currently only available with the std feature).

This is useful for strategies which have a tendency to produce duplicate values, or for tests where shrinking can take a very long time due to exploring the same output multiple times.

When caching is enabled, generated values themselves are not stored, so this does not pose a risk of memory exhaustion for large test inputs unless using extraordinarily large test case counts.

Caching incurs its own overhead, and may very well make your test run more slowly.

verbose: u32

Set to non-zero values to cause proptest to emit human-targeted messages to stderr as it runs.

Greater values cause greater amounts of logs to be emitted. The exact meaning of certain levels other than 0 is subject to change.

• 0: No extra output.
• 1: Log test failure messages. In state machine tests, this level is used to print transitions.
• 2: Trace low-level details.

This is only available with the std feature (enabled by default) since on nostd proptest has no way to produce output.

The default is 0, which can be overridden by setting the PROPTEST_VERBOSE environment variable. (The variable is only considered when the std feature is enabled, which it is by default.)

rng_algorithm: RngAlgorithm

The RNG algorithm to use when not using a user-provided RNG.

The default is RngAlgorithm::default(), which can be overridden by setting the PROPTEST_RNG_ALGORITHM environment variable to one of the following:

• xs — RngAlgorithm::XorShift
• cc — RngAlgorithm::ChaCha

(The variable is only considered when the std feature is enabled, which it is by default.)