zecsy/tests/zecsy.cpp

#include <catch2/catch_test_macros.hpp>
#include <string>
#define CATCH_CONFIG_MAIN
#include <catch2/catch_all.hpp>

#include "../zecsy.hpp"

using namespace zecsy;

TEST_CASE("Create a single entity and verify its existence")
{
    world w;

    auto e = w.make_entity();

    REQUIRE(w.is_alive(e));
}

TEST_CASE("Destroy an entity and ensure it no longer exists in the world")
{
    world w;

    auto e = w.make_entity();
    w.destroy_entity(e);

    REQUIRE_FALSE(w.is_alive(e));
}

TEST_CASE("Entity #0 should be reserved and never used")
{
    world w;

    auto e = w.make_entity();

    REQUIRE(e != 0);
    REQUIRE_FALSE(w.is_alive(0));
}

struct ChoosenOne
{
};

TEST_CASE("Entity shouldn't have a component that wasn't attached to it")
{
    world w;

    auto e = w.make_entity();

    REQUIRE_FALSE(w.has<ChoosenOne>(e));
}

TEST_CASE("Attempt of getting non-owned component should throw")
{
    world w;

    auto e = w.make_entity();

    REQUIRE_THROWS(w.get<ChoosenOne>(e));
}

TEST_CASE("Attach a simple component to an entity and verify it is correctly "
          "associated")
{
    world w;

    auto e1 = w.make_entity();
    w.set(e1, ChoosenOne{});

    REQUIRE(w.has<ChoosenOne>(e1));

    auto e2 = w.make_entity();
    w.set(e2, ChoosenOne{});

    REQUIRE(w.has<ChoosenOne>(e2));
}

struct Name
{
    std::string value;
};

TEST_CASE("Retrieve a component from an entity and verify its data matches "
          "what was set")
{
    world w;

    auto e = w.make_entity();
    w.set(e, Name{"zecsy!"});

    REQUIRE(w.get<Name>(e).value == "zecsy!");

    w.get<Name>(e).value = "super-zecsy!";

    REQUIRE(w.get<Name>(e).value == "super-zecsy!");
}

TEST_CASE(
    "Remove a component from an entity and verify it is no longer attached")
{
    world w;

    auto e = w.make_entity();
    w.set(e, ChoosenOne{});
    REQUIRE_NOTHROW(w.remove<ChoosenOne>(e));

    REQUIRE_FALSE(w.has<ChoosenOne>(e));

    w.set(e, ChoosenOne{});
    REQUIRE_NOTHROW(w.remove<ChoosenOne>(e));

    REQUIRE_FALSE(w.has<ChoosenOne>(e));
}

TEST_CASE("Addresses of removed components should be reused")
{
    world w;
    std::vector<entity_id> entities;
    std::vector<ChoosenOne*> addr;

    const int N = 4;

    for(int i = 0; i < 2; ++i)
    {
        for(int j = 0; j < N; ++j)
        {
            entities.emplace_back(w.make_entity());
            w.set<ChoosenOne>(entities.back());
        }

        if(addr.empty())
        {
            for(int j = 0; j < N; ++j)
            {
                addr.emplace_back(&w.get<ChoosenOne>(entities[j]));
            }
        }
        else
        {
            /*
             * Gotta reverse it because now we reuse ids in LIFO order
             */
            std::reverse(addr.begin(), addr.end());
            
            for(int j = 0; j < N; ++j)
            {
                REQUIRE(&w.get<ChoosenOne>(entities[j]) == addr[j]);
            }
        }

        for(auto e: entities)
        {
            w.remove<ChoosenOne>(e);
        }
        entities.clear();
    }
}

TEST_CASE("Attach multiple components to an entity and verify all are "
          "correctly stored and retrievable")
{
    world w;

    auto e = w.make_entity();
    w.set(e, ChoosenOne{}, Name{"zecsy"});

    REQUIRE(w.has<ChoosenOne, Name>(e));

    w.remove<ChoosenOne, Name>(e);

    REQUIRE_FALSE(w.has<ChoosenOne, Name>(e));
    REQUIRE_FALSE(w.has<ChoosenOne>(e));
    REQUIRE_FALSE(w.has<Name>(e));
}

TEST_CASE("Create a simple system that processes entities with a specific "
          "component and verify it executes correctly")
{
    struct Component
    {
        int value = 0;
    };

    world w;
    auto e0 = w.make_entity(), e1 = w.make_entity();

    w.set<Component>(e0); // or e0.set(Component{})
    w.set(e1, Component{20});

    REQUIRE(w.get<Component>(e0).value == 0);
    REQUIRE(w.get<Component>(e1).value == 20);

    /*
     * Really wanna deduce it to w.query([](Component&){}),
     * but I have some troubles with it
     */
    w.query<Component>([](Component& c) { c.value++; });

    REQUIRE(w.get<Component>(e0).value == 1);
    REQUIRE(w.get<Component>(e1).value == 21);
}

TEST_CASE("Test a systems ability to query and process only entities with a "
          "specific combination of components")
{
    struct C0
    {
        int value = 0;
    };

    struct C1
    {
        int value = 10;
    };

    world w;

    auto e0 = w.make_entity();
    w.set(e0, C0{}, C1{});

    auto e1 = w.make_entity();
    w.set(e1, C0{});

    auto e2 = w.make_entity();
    w.set(e2, C1{});

    int count = 0;

    REQUIRE(w.get<C0>(e0).value == 0);
    REQUIRE(w.get<C1>(e0).value == 10);

    w.query<C0, C1>([&count](C0& c0, C1& c1)
    {
        c0.value++;
        c1.value++;
        count++;
    });

    REQUIRE(count == 1);

    REQUIRE(w.get<C0>(e0).value == 1);
    REQUIRE(w.get<C1>(e0).value == 11);

    REQUIRE(w.get<C0>(e1).value == 0);
    REQUIRE(w.get<C1>(e2).value == 10);

    REQUIRE_FALSE(w.has<C1>(e1));
    REQUIRE_FALSE(w.has<C0>(e2));
}

TEST_CASE("Systems execute at correct frequencies")
{
    world w;
    system_scheduler scheduler;

    int fast_count = 0;
    int slow_count = 0;

    // Add a fast system (60 Hz)
    scheduler.add_system(60, [&](float dt) { fast_count++; });

    // Add a slow system (1 Hz)
    scheduler.add_system(1, [&](float dt) { slow_count++; });

    // Simulate 2 seconds of updates at 120 FPS
    for(int i = 0; i < 240; ++i)
    {
        scheduler.update(1.0f / 120.0f);
    }

    // Verify counts
    REQUIRE(fast_count == 120); // 60 Hz system should execute 60 times
    REQUIRE(slow_count == 2);   // 1 Hz system should execute 1 time
}

TEST_CASE("Systems handle zero-frequency gracefully")
{
    world w;
    system_scheduler scheduler;

    int zero_count = 0;

    // Add a zero-frequency system (should never execute)
    scheduler.add_system(0, [&](float dt) { zero_count++; });

    // Simulate 1 second of updates at 60 FPS
    for(int i = 0; i < 60; ++i)
    {
        scheduler.update(1.0f / 60.0f);
    }

    // Verify zero-frequency system never executes
    REQUIRE(zero_count == 0);
}

TEST_CASE("Systems handle varying update rates")
{
    world w;
    system_scheduler scheduler;

    int varying_count = 0;

    // Add a system with varying frequency (10 Hz)
    scheduler.add_system(10, [&](float dt) { varying_count++; });

    // Simulate 1 second of updates at 30 FPS
    for(int i = 0; i < 30; ++i)
    {
        scheduler.update(1.0f / 30.0f);
    }

    // Verify varying-frequency system executes 10 times
    REQUIRE(varying_count == 10);
}

TEST_CASE("Systems handle large time steps")
{
    world w;
    system_scheduler scheduler;

    int large_step_count = 0;

    // Add a system (1 Hz)
    scheduler.add_system(1, [&](float dt) { large_step_count++; });

    // Simulate a large time step (2 seconds)
    scheduler.update(2.0f);

    // Verify system executes twice (accumulator handles large steps)
    REQUIRE(large_step_count == 2);
}

TEST_CASE("Systems handle multiple frequencies")
{
    world w;
    system_scheduler scheduler;

    int fast_count = 0;
    int medium_count = 0;
    int slow_count = 0;

    // Add systems with different frequencies
    scheduler.add_system(60, [&](float dt) { fast_count++; });
    scheduler.add_system(30, [&](float dt) { medium_count++; });
    scheduler.add_system(1, [&](float dt) { slow_count++; });

    // Simulate 1 second of updates at 120 FPS
    for(int i = 0; i < 120; ++i)
    {
        scheduler.update(1.0f / 120.0f);
    }

    // Verify counts
    REQUIRE(fast_count == 60);   // 60 Hz system
    REQUIRE(medium_count == 30); // 30 Hz system
    REQUIRE(slow_count == 1);    // 1 Hz system
}

TEST_CASE("Systems handle fractional frequencies")
{
    world w;
    system_scheduler scheduler;

    int fractional_count = 0;

    // Add a system with fractional frequency (0.5 Hz)
    scheduler.add_system(0.5f, [&](float dt) { fractional_count++; });

    // Simulate 4 seconds of updates at 60 FPS
    for(int i = 0; i < 240; ++i)
    {
        scheduler.update(1.0f / 60.0f);
    }

    // Verify fractional-frequency system executes twice (0.5 Hz = 2 times in 4
    // seconds)
    REQUIRE(fractional_count == 2);
}

TEST_CASE("Systems handle zero delta time")
{
    world w;
    system_scheduler scheduler;

    int zero_dt_count = 0;

    // Add a system (1 Hz)
    scheduler.add_system(1, [&](float dt) { zero_dt_count++; });

    // Simulate zero delta time
    scheduler.update(0.0f);

    // Verify system does not execute
    REQUIRE(zero_dt_count == 0);
}

TEST_CASE("Systems handle negative delta time")
{
    world w;
    system_scheduler scheduler;

    int count = 0;

    // Add a system (1 Hz)
    scheduler.add_system(1, [&](float dt) { count++; });

    // Simulate negative delta time
    scheduler.update(-1.0f);

    // Verify system does not execute
    REQUIRE(count == 0);

    scheduler.update(2.0f);

    REQUIRE(count == 2);
}