抓住

Catch 是一个仅限标题的库，允许你同时使用 TDD 和 BDD 单元测试样式。

以下代码段来自此链接的 Catch 文档页面 ：

SCENARIO( "vectors can be sized and resized", "[vector]" ) {
    GIVEN( "A vector with some items" ) {
        std::vector v( 5 );
        
        REQUIRE( `v.size()` == 5 );
        REQUIRE( `v.capacity()` >= 5 );
        
        WHEN( "the size is increased" ) {
            v.resize( 10 );
            
            THEN( "the size and capacity change" ) {
                REQUIRE( `v.size()` == 10 );
                REQUIRE( `v.capacity()` >= 10 );
            }
        }
        WHEN( "the size is reduced" ) {
            v.resize( 0 );
            
            THEN( "the size changes but not capacity" ) {
                REQUIRE( `v.size()` == 0 );
                REQUIRE( `v.capacity()` >= 5 );
            }
        }
        WHEN( "more capacity is reserved" ) {
            v.reserve( 10 );
            
            THEN( "the capacity changes but not the size" ) {
                REQUIRE( `v.size()` == 5 );
                REQUIRE( `v.capacity()` >= 10 );
            }
        }
        WHEN( "less capacity is reserved" ) {
            v.reserve( 0 );
            
            THEN( "neither size nor capacity are changed" ) {
                REQUIRE( `v.size()` == 5 );
                REQUIRE( `v.capacity()` >= 5 );
            }
        }
    }
}

方便的是，这些测试在运行时将报告如下：

Scenario: vectors can be sized and resized
     Given: A vector with some items
      When: more capacity is reserved
      Then: the capacity changes but not the size