How to run multiple tests that use flag.Var() without "flag redefined" panic

[sheale...@gmail.com]

The code I am testing uses command line flags:
 

// config.go 

package config

import "flag"

func CreateConfig() (ConfigStruct, error) {
    configPath := flag.String("config", defaultConfig, "config file path")
   ...
}

The thing is, if I run multiple tests of this code, I get a flag-redefined error:

// config_test.go
package config_test
import "my/path/config"
func TestCreateConfig() {
    config.CreateConfig()
    ...
}

E.g.

/tmp/go-build887413297/mypath/config/_test/config.test flag redefined: custom_config
/usr/local/go/src/runtime/panic.go:387

I believe this is because I only import the flag package once, so any call to flag.Var() looks at the same f.formal map.

Being only able to run one test is almost like not being able to run any at all, so I'm eager to hear how I can work around this or where my (misunderstanding is leading me astray.

Thanks

[Ian Lance Taylor]

On Thu, Jan 8, 2015 at 3:14 PM, <sheale...@gmail.com> wrote:
>
> The code I am testing uses command line flags:
>
>>
>> // config.go
>>
>> package config
>>
>> import "flag"
>>
>> func CreateConfig() (ConfigStruct, error) {
>> configPath := flag.String("config", defaultConfig, "config file path")
>> ...
>> }

Is there any reason to only create the flag in CreateConfig? Why not
use a global variable?

Ian

[sheale...@gmail.com]

1. I created the flag in the CreateConfig() function to keep the whole config getting/maintaining cordoned off in the config package so I can inject it around (nice for testing, etc).

2. I also realized where my misunderstanding lay. I solved my problem by giving the config package an init() function that calls flag.String(), and then waiting to call flag.Parse() in config.CreateConfig():

// config.go
package config
import "flag"

val configPath *string
func init() {
 configPath := flag.String("config", "", "config file path")
}
func CreateConfig() (ConfigStruct, error) {
 flag.Parse()
 use(*configPath)
 ...
}

Then I have no problems calling CreateConfig multiple times, as I wanted to.

// config_test.go
package config_test
import "my/path/config"
func TestCreateConfig() {
    config.CreateConfig()
    ...
}

Thanks!

[Matt Harden]

You could also create a new FlagSet in CreateConfig flags := flag.NewFlagSet(os.Args[0], flag.ExitOnError) and use that instead of the global flagset flag.CommandLine.

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