zig/doc/langref/test_fibonacci_comptime_unreachable.zig

const assert = @import("std").debug.assert;

fn fibonacci(index: i32) i32 {
    if (index < 2) return index;
    return fibonacci(index - 1) + fibonacci(index - 2);
}

test "fibonacci" {
    try comptime assert(fibonacci(7) == 99999);
}

// test_error=reached unreachable