Visual Studio“调试单元测试”无法达到断点

When using Visual Studio 2008 and debugging my unit tests... sometimes the debugger works fine. However very often after modifying some code then clicking "Debug Unit Test" Visual Studio will fail to hit the breakpoints in the code. The debugger basically hangs and eventually the tests runs with the new code anyway, but never stops to let me see what is going on.When using Visual Studio 2008 and debugging my