Configuring the number of tests cases requried

The default number of successful test cases that must execute for a test as a whole to pass is currently 256. If you are not satisfied with this and want to run more or fewer, there are a few ways to do this.

The first way is to set the environment-variable PROPTEST_CASES to a value that can be successfully parsed as a u32. The value you set to this variable is now the new default.

Another way is to use #![proptest_config(expr)] inside proptest! where expr : Config. To only change the number of test cases, you can simply write:

use proptest::prelude::*;

fn add(a: i32, b: i32) -> i32 { a + b }

proptest! {
    // The next line modifies the number of tests.
    fn test_add(a in 0..1000i32, b in 0..1000i32) {
        let sum = add(a, b);
        assert!(sum >= a);
        assert!(sum >= b);

fn main() { test_add(); }

Through the same proptest_config mechanism you may fine-tune your configuration through the Config type. See its documentation for more information.