我想对下列这个Component的UI进行单元测试。其中有一个自定义的cxUrl pipe，在单元测试时，我需要对其进行Mock：
解决方法，在单元测试的实现代码里，创建一个用@Pipe修饰过的MockUrlPipe，在其transform方法里什么都不做即可：
/** * Invokes a pipe with 1 arguments. * * This instruction acts as a guard to {@link PipeTransform#transform} invoking * the pipe only when an input to the pipe changes. * * @param index Pipe index where the pipe was stored on creation. * @param slotOffset the offset in the reserved slot space * @param v1 1st argument to {@link PipeTransform#transform}. * * @codeGenApi */
/** * If the value of the provided exp has changed, calls the pure function to return * an updated value. Or if the value has not changed, returns cached value. * * @param lView LView in which the function is being executed. * @param bindingRoot Binding root index. * @param slotOffset the offset from binding root to the reserved slot * @param pureFn Function that returns an updated value * @param exp Updated expression value * @param thisArg Optional calling context of pureFn * @returns Updated or cached value */
绑定表达式的值发生变化时，触发pureFunction1Internal，重新计算绑定的值：
