Crate allocation_counter

This crate provides a method to count and test the number of allocations while running some code.

Example

Add as a dependency - since including the trait replaces the global memory allocator, you most likely want it gated behind a feature.

[features]
count-allocations = ["allocation-counter"]

[dependencies]
allocation-counter = { version = "0", optional = true }

Tests can now be written to assert that the number of desired memory allocations are not exceeded.

#[cfg(feature = "count-allocations")]
#[test]
pub fn no_memory_allocations() {
    let allocations = allocation_counter::count(|| {
        code_that_should_not_allocate_memory();
    });
    assert_eq!(allocations, 0);

    // Or use this utility method in this case:
    allocation_counter::assert_no_allocations(|| {
        code_that_should_not_allocate_memory();
    });

    // Can also allow a certain number of allocations:
    allocation_counter::assert_max_allocations(10 || {
        code_that_should_not_allocate_much();
    });

    // Can also assert on a range, useful to adjust
    // test expectations over time:
    allocation_counter::assert_num_allocations(500..600 || {
        code_that_should_not_allocate_much();
    });

    // It's possible to opt out of counting allocations
    // for certain parts of the code flow:
    allocation_counter::assert_no_allocations(|| {
        code_that_should_not_allocate();
        allocation_counter::avoid_counting(|| {
            external_code_that_should_not_be_tested();
        });
        code_that_should_not_allocate();
    });
}

Run the tests with the necessary feature enabled.

cargo test --features count-allocations

Functions

• assert_max_allocations
  Run a closure and assert that the number of memory allocations are below a limit.
• assert_no_allocations
  Run a closure and assert that no memory allocations were made.
• assert_num_allocations
  Run a closure and assert that the number of memory allocations are inside a range.
• avoid_counting
  Opt out of counting allocations while running some code.
• count
  Run a closure while counting the performed memory allocations.