Crate double

Double is a fully-featured mocking library for mocking Trait implementations.

The Double struct tracks function call arguments and specifies return values or function overrides.

This library is based off iredelmeier's initial mocking implementation. Massive thanks to her implementation for inpsiring me to work on this. Her repo can be found here:

https://github.com/iredelmeier/pseudo

If you're interested in testing, check out her other repositories too!

Examples

#[macro_use]
extern crate double;

// Code under test
trait BalanceSheet {
    fn profit(&self, revenue: u32, costs: u32) -> i32;
}

fn get_profit(revenue: u32, costs: u32, balance_sheet: &BalanceSheet) -> i32 {
    balance_sheet.profit(revenue, costs)
}

// Tests which uses a mock BalanceSheet
mock_trait!(
    MockBalanceSheet,
    profit(u32, u32) -> i32);
impl BalanceSheet for MockBalanceSheet {
    mock_method!(profit(&self, revenue: u32, costs: u32) -> i32);
}

fn test_weighting_is_applied() {
    // GIVEN:
    let sheet = MockBalanceSheet::default();
    sheet.profit.return_value(250);
    // WHEN:
    let profit = get_profit(500, 250, &sheet);
    // THEN:
    assert_eq!(250, profit);
}

fn test_correct_args_passed_to_balance_sheet() {
    // GIVEN:
    let sheet = MockBalanceSheet::default();
    // WHEN:
    let _ = get_profit(500, 250, &sheet);
    // THEN:
    sheet.profit.has_calls_exactly_in_order(vec!((500, 250)));
}

// Executing tests
fn main() {
    test_weighting_is_applied();
    test_correct_args_passed_to_balance_sheet();
}

Macros

mock_method
mock_trait

Structs

Mock	Used for tracking function call arguments and specifying a predetermined return value or mock function.

Type Definitions

Double