Nekrolm

Mock testing in Rust projects

Rust usually gives you a pleasant experience: if it compiles — it works. But strong type checking doesn’t eliminate necessity of testing. Especially if your code deals with some external dependencies:

• Have your checked the behaviour of your code on all error paths? May there be typo, incorrect condition, that passes type checks but contradicts with your intentions?
• What if dependency returns success on the first call, but error for the second?
• What if there’s sudden network issue?

To cover such cases there is a common approach — substitute, or “mock”, your dependencies by special, configurable test objects with same interface. And here our story begins.

Nekrolm

Why unsafe is unsafe

Once I had seen this function. It was a nice function, but there is a problem

pub fn encode_logs(logs: impl IntoIterator<Item = impl AsRef<str>>) -> String {
    logs.into_iter().map(|line|
        line.as_ref()
            .replace("\\", "\\\\")
            .replace("\n", "\\n")

Nekrolm

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb cccccccccccccccccccccccccccccccccccccccccccccccccccc ddddddddddddddd eeeeeeeeeeeeeeeee ffffffffffffff ggggggggggg hhhhhhhhhhhhhhhhhhhhhhhhhhhhh iiiiiiiiiiiiiiiiiiiiiiiiiiiii jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk llllllllllllllllllllllllllllllllllllllllllllll mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn ooooooooooooooooooooooooooooooooo pppppppppppppppppppppppppppppppppppppppppp qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq rrrrrrrrrrrrrrrrrrrrrrrrrrrrr ssssssssssssssssssssssssssssss tttttttttttttttttttttttttt uuuuuuuuuuuuuuuuuuuuuuuuu vvvvvvvvvvvvvvvvvvvvvvvvvvvvv wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm 1234567890 QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm123456

Nekrolm

#include <stdlib.h>
#include <cstdint>

#include <string>
#include <vector>
#include <map>
#include <iostream> 
#include <functional>
#include <utility>
#include <memory>

Nekrolm

// https://godbolt.org/z/hfcnTfaz8
#include <cstdint>
#include <array>
#include <cstddef>
#include <ranges>
#include <algorithm>
#include <utility>
#include <format>
#include <string_view>
#include <print>

Nekrolm

#include <string>
#include <string_view>
#include <iostream>
#include <concepts>


void check_length(std::string_view sv)
{ std::cout << "check len\n"; }
void check_content(std::string_view sv) 
{ std::cout << "check content\n"; }

Nekrolm

// https://godbolt.org/z/cfE7sh3jT
#include <type_traits>
#include <utility>
#include <new>
#include <stdexcept>
#include <functional>
#include <print>
#include <string>
#include <vector>

Nekrolm

Мерзкий С-callback

Итак вы программист на высокоуровневых языках: Python, Java, C++ (прости господи)... И вот однажды вам, по долгу службы, выпадает необходимость взять и написать код на C/C++ с использованием прекрасной чистой C библиотеки... мы будем ее звать X.

В этой замечательной библиотеке есть функция

struct power_management_ctx_t; // opaque struct

Nekrolm

Как перекладывают вектора

При работе над разными числодробилками, анализирующими последовательности, применяющими фильтры к картинкам, cчитающим свертки и проч, периодически возникает необходимость преобразовать массив целых чисел в массив чисел с плавающей точкой и наоборот.

На C++ это может выглядеть так

std::vector<float> to_floats(std::vector<int> input) {
    std::vector<float> result(input.size());
    std::transform(begin(input), end(input), begin(result), [](int x) -> float { return x; });

Nekrolm

#include <memory>
#include <type_traits>
#include <concepts>
#include <span>
#include <functional>
#include <iostream>

struct Context {
    std::string_view body;
    std::string_view headers;