对 API 进行单元测试

Question

我正在编写的库中有以下渲染器 API：

class EXPORT Renderer {
  public:
    Renderer(const Renderer &) = delete;
    Renderer &operator=(const Renderer &) = delete;
    virtual ~Renderer();

  protected:
    Renderer() = default;

  public:
    [[nodiscard]] static std::unique_ptr<Renderer> create(const RendererDescriptor &descriptor);

    [[nodiscard]] virtual std::unique_ptr<SwapChain> createSwapChain(const SwapChainDescriptor &descriptor, const Window &window) = 0;

    [[nodiscard]] virtual std::unique_ptr<Buffer> createVertexBuffer(const BufferDescriptor &descriptor, const VertexFormat &format) = 0;

    [[nodiscard]] virtual std::unique_ptr<Buffer> createIndexBuffer(const BufferDescriptor &descriptor, Format format) = 0;

    [[nodiscard]] virtual std::unique_ptr<Shader> createShaderFromString(const ShaderDescriptor &descriptor, std::string_view source) = 0;

    [[nodiscard]] virtual std::unique_ptr<PipelineState> createPipelineState(const PipelineStateDescriptor &descriptor) = 0;

    [[nodiscard]] virtual std::unique_ptr<CommandList> createCommandList(const CommandListDescriptor &descriptor) = 0;

    [[nodiscard]] virtual std::unique_ptr<Texture> createTexture(const TextureDescriptor &descriptor) = 0;

    [[nodiscard]] virtual std::unique_ptr<RenderTarget> createRenderTarget(const RenderTargetDescriptor &descriptor) = 0;

    [[nodiscard]] virtual std::unique_ptr<RenderPass> createRenderPass(const RenderPassDescriptor &descriptor) = 0;
};

此渲染器 API 在另一个库中实现，例如 OpenGL 后端：

class GLRenderer final : public Renderer {
  public:
    explicit GLRenderer(const RendererDescriptor &descriptor);

    std::unique_ptr<SwapChain> createSwapChain(const SwapChainDescriptor &descriptor, const Window &window) override;

    std::unique_ptr<Buffer> createVertexBuffer(const BufferDescriptor &descriptor, const VertexFormat &format) override;

    std::unique_ptr<Buffer> createIndexBuffer(const BufferDescriptor &descriptor, Format format) override;

    std::unique_ptr<Shader> createShaderFromString(const ShaderDescriptor &descriptor, std::string_view source) override;

    std::unique_ptr<PipelineState> createPipelineState(const PipelineStateDescriptor &descriptor) override;

    std::unique_ptr<CommandList> createCommandList(const CommandListDescriptor &descriptor) override;

    std::unique_ptr<Texture> createTexture(const TextureDescriptor &descriptor) override;

    std::unique_ptr<RenderTarget> createRenderTarget(const RenderTargetDescriptor &descriptor) override;

    std::unique_ptr<RenderPass> createRenderPass(const RenderPassDescriptor &descriptor) override;

  private:
// private members
};

在

Renderer::create

工厂方法中加载此 OpenGL 后端库，并分配

GLRenderer

然后返回。我应该如何使用 GoogleTest 对该 API 进行单元测试？

Answer 1

根据您在评论中的请求，对于针对其公共接口测试多个给定实现的一方面，我制作了一个带有一个玩具接口和两个玩具实现的小示例。希望这可以为您提供一个继续前进的起点（您可以在编译器资源管理器上看到相同的代码）：

#include <memory>
#include <gtest/gtest.h>

class interface {
    public:
    virtual ~interface()=default;
    virtual long tripleNum(long) =0;
};

class impl0 : public interface {
    public:
    virtual ~impl0()=default;
    long tripleNum(long const inp) override {
        return inp+inp+inp;
    }
};

class impl1 : public interface {
    public:
    virtual ~impl1()=default;
    long tripleNum(long const inp) override {
        return inp*3;
    }
};

static const std::tuple<std::shared_ptr<impl0>,std::shared_ptr<impl1>> PARAMS{
    std::make_shared<impl0>(), std::make_shared<impl1>() };
using TEST_TYPES = ::testing::Types<std::shared_ptr<impl0>,std::shared_ptr<impl1>>;

template <typename T> class ImplTests : public testing::Test
{
  protected:
    ImplTests() : param(std::static_pointer_cast<interface>(std::get<T>(PARAMS))) {}
    std::shared_ptr<interface> param;
};
TYPED_TEST_SUITE(ImplTests, TEST_TYPES);

TYPED_TEST(ImplTests, ensure_that_triple_returns_three_times_the_input) {
    EXPECT_EQ(27,this->param->tripleNum(9));
}
int main(int argc, char *argv[]) {
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

当然，有些事情可以用更优雅的方式完成（例如，这里可能不需要

shared_ptr

）。无论如何，这个例子应该能说明问题。