测试从恐慌中恢复

Question

I want to test a constructor, but in case some data is not provided I need to panic, how can I recover from that panic in testing?

At the moment I've added in my TestNew func a defer with recover, but in case an element from my map has an empty URL the rest will not be checked.

t.go

package testing

type test {
  url string
}

func New(ops map[string]string) *test {
  if ops["url"] == "" {
    panic("Url missing")
  }
  var t = new(test)
  t.url = ops["url"]
  return t
}

t_test.go

package testing

type testTest map[string]string
var testingTest = []testTest {
  testTest {
    "url": "test",
  },
  testTest{
    "url": "",
  },
}

func NewTest(t *testing.T) {
  defer func() {
    recover()
  }()

  for _, e := range testingTest {
    url := New(e)
    url.hasUrl(t, e["url"])
  }
}

func (s *test) hasUrl(t *testing.T, u string) {
  if s.url != u {
    t.Errorf("Expected %s to be equal with %s", s.url, u)
  }
}

Answer 1

I would say that designing API for library that relies on panic/recover is not a right way. Go has error pattern so if the method New cannot test, it can return the status instead.

package testing

type test {
  url string
}

func New(ops map[string]string) (*test, bool) {
  if ops["url"] == "" {
    return nil, false
  }
  var t = new(test)
  t.url = ops["url"]
  return t, true
}

and then

for _, e := range testingTest {
  url, ok := New(e)
  if ok {
    url.hasUrl(t, e["url"])
  }
}

If you insist on using panic, then you can wrap the invocation into function and recover in it. But then you still would need to provide the status to the caller.

package main

import "fmt"

func test(e int) {
    if e == 2 {
        panic("panic!")
    }
}

func main() {
    for _, e := range []int{1, 2, 3} {
        func() {
            defer func() { recover() }()
            test(e)
            fmt.Println("testing", e)
        }()
    }
}