To mock a handler:
```go
web.RouteMock(web.MockAfterMiddlewares, func(ctx *context.Context) {
// ...
})
defer web.RouteMockReset()
```
It helps:
* Test the middleware's behavior (assert the ctx.Data, etc)
* Mock the middleware's behavior (prepare some context data for handler)
* Mock the handler's response for some test cases, especially for some
integration tests and e2e tests.
wxiaoguang
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