Struct Faker for Go
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Update Fix example using user_name tag
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Circle CI Godoc Go Report Card

Fako is a library intended to fake Golang structs with fake but coherent data, Fako maps struct field tags and generates fake data accordingly.

We find it useful when writing specs to generate fake database data, hope you too.


This is an example of how Fako works.


type User struct {
    Name     string `fako:"full_name"`
  	Username string `fako:"user_name"`
  	Email    string `fako:"email_address"`//Notice the fako:"email_address" tag
  	Phone    string `fako:"phone"`
  	Password string `fako:"simple_password"`
  	Address  string `fako:"street_address"`

func main(){
  var user User

  // This prints something like
  // or another valid email

  var userWithOnlyEmail User
  fako.FillOnly(&userWithOnlyEmail, "Email")
  //This will fill all only the email

  var userWithoutEmail User
  fako.FillExcept(&userWithoutEmail, "Email")
  //This will fill all the fields except the email


Fako provides 3 built in functions Fill, FillOnly, and FillExcept, please go to godoc for details.

Fako support most of the fields on the fake library, below you can see a list of the field types you can use.

  • brand
  • character
  • characters
  • city
  • color
  • company
  • continent
  • country
  • credit_card_type
  • currency
  • currency_code
  • digits
  • domain_name
  • domain_zone
  • email_address
  • email_body
  • email_subject
  • female_first_name
  • female_full_name
  • female_full_name_with_prefix
  • female_full_name_with_suffix
  • female_last_name
  • female_patronymic
  • first_name
  • full_name
  • full_name_with_prefix
  • full_name_with_suffix
  • gender
  • gender_abbrev
  • hex_color
  • hex_color_short
  • ip_v4
  • industry
  • job_title
  • language
  • last_name
  • latitude_direction
  • longitude_direction
  • male_first_name
  • male_full_name
  • male_full_name_with_prefix
  • male_full_name_with_suffix
  • male_last_name
  • male_patronymic
  • model
  • month
  • month_short
  • paragraph
  • paragraphs
  • patronymic
  • phone
  • product
  • product_name
  • sentence
  • sentences
  • simple_password
  • state
  • state_abbrev
  • street
  • street_address
  • title
  • top_level_domain
  • user_name
  • week_day
  • week_day_short
  • word
  • words
  • zip

Custom Generators

Fako provides a function called Register to add custom data generators in case you need something that our provided generators cannot cover.

To add a custom generator simply call the Register function as in the following example:


type User struct {
    Name     string `fako:"full_name"`
    Username string `fako:"user_name"`
    Email    string `fako:"email_address"`//Notice the fako:"email_address" tag
    Phone    string `fako:"phone"`
    Password string `fako:"simple_password"`
    Address  string `fako:"street_address"`

    AValue   string `fako:"a_gen"`

func main(){
  fako.Register("a_gen", func() string {
    return "My Value"

  var user User
  fmt.Println(user.AValue) //should print My Value

When using custom generators please keep the following in mind:

  1. Call Register function before calling Fill and its brothers.
  2. Custom generators override base generators, if you pick the same name as one of the existing generators, we will override the existing generator with yours.


Sometimes you just want to generate random data inside a struct, for those cases you wont want to fill fako types (yes, we understand that part). Fako provides you a Fuzz function you can use to fuzz your structs with random data that simply matches the struct's field types.

You can use it as in the following example:

import "fako"

type Instance struct {
   Name string
   Number int

func main(){
  instance := Instance{}
  fako.Fuzz(&instance) // This fills your instance variable

Note, Fuzz function works for the following types string, bool, int, int32, int64, float32, float64. other types like Array or Chan are out of our scope.


As you may have noticed this is based on fake library, which does all the work to generate data.


Fako is Copyright © 2008-2015 Wawandco SAS. It is free software, and may be redistributed under the terms specified in the LICENSE file.