extern crate civil;

// Calculus Tests
use civil::calc::calculus;

const PRECISION: f64 = 0.1;

#[test]
fn calc_constants_exist() {
    assert!(calculus::WEIGHTS[0] == 1.0)
}

#[test]
fn second_order_integration_works() {
    fn simple_function(x: f64) -> f64 {
        x.powi(2)
    }
    let result = dbg!(calculus::integrate(simple_function, 2, 0.0_f64, 1.0_f64));
    assert!((result - 0.33) < PRECISION)
}

#[test]
fn first_order_integration_works() {
    fn simple_function(x: f64) -> f64 {
        x
    }
    let result = dbg!(calculus::integrate(simple_function, 1, 1.0_f64, 2.0_f64) as f64);
    assert!((result - 1.5).abs() < PRECISION)
}

#[test]
fn first_order_integration_from_zero_to_one() {
    fn simple_function(x: f64) -> f64 {
        x + 1.0_f64
    }
    let result = dbg!(calculus::integrate(simple_function, 1, 0.0_f64, 1.0_f64));
    assert!((result as f64 - 1.5).abs() < PRECISION)
}

#[test]
fn zero_order_integration_works() {
    fn simple_function(_x: f64) -> f64 {
        2.0
    }
    let result = dbg!(calculus::integrate(simple_function, 0, 0.0_f64, 1.0_f64));
    assert!((result - 2.0) < PRECISION)
}