由于项目需要，学习使用cobertura检查junit测试覆盖率。 结果ant总是报错：
BUILD FAILEDbuild.xml:54: Problem: failed to create task or typecobertura-instrumentCause: The name is undefined.Action: Check the spelling.Action: Check that any custom tasks/types have been declared.Action: Check that any<presetdef>/<macrodef>declarations have taken place.
搜了一些文章，都无解，最后看cobertura的example，找到病根。 解决方法： 将<taskdef classpath=“cobertura.classpath"resource=“tasks.properties” />改成<taskdef classpathref=“cobertura.classpath"resource=“tasks.properties” />就好了。