so i have function without routine
func ContainsWithoutGoroutine() return {
someFunction()
return
}
and there is mock of someFunction
type DummyMock struct {
mock.mock
}
func(t *DummyMock) someFunction() {
//
}
to write the unit test for ContainsWithoutGoroutine we could easily mock someFunction and test it.
and now suppose i added a function with goroutine ContainsGoroutine
func ContainsGoroutine() return {
go func() {
someFunction()
}()
return
}
could not able to write unit test until we update the mock to something like this
type DummyMock struct {
mock.mock
Wg sync.WaitGroup
}
func(t *DummyMock) someFunction() {
defer t.Wg.Done()
//
}
and in the unit test of ContainsGoroutine need to add additional mock.Add(1) mock.Wg.Wait
after that unit test for ContainsGoroutine will work, but ContainsWithoutGoroutine will start failing
i know we could add same mock.Add(1) mock.Wg.Wait for the unit test of ContainsWithoutGoroutine to make it work , which i don't want to do that , As consider for the case where someFunction has been already being used in lot of places where there was no go routine and all that unit tests need to be changed.
is there a better way to structure this or maybe write unit test differently
I have a codebase that is roughly as follows
type Service struct {
Repo repo // An interface that contains both FunctionOne and FunctionTwo
GoRoutineWaitgroup *sync.WaitGroup
}
func (impl *Service) MyFunction(s string) bool {
a := impl.Repo.FunctionOne()
b := impl.Repo.FunctionTwo()
fmt.Println("Executed Function One and Function two")
go impl.validateMyFunction(a,b)
return true
}
func (impl *Service) validateMyFunction(a string,b string) {
defer helpers.PanicHandler()
impl.GoRoutineWaitgroup.Add(1)
defer impl.GoRoutineWaitgroup.Done()
fmt.Println("a and b are validated")
}
And I wrote unit tests as something similar to this.
func TestMyFunction(t *testing.T) {
ms := &Service{}
test := []struct{
input string
output bool
case string
}{
{"a", true, sample}
}
}
for _, test := range tests {
t.Run(test.case, func(t *testing.T) {
mockRepo := new(mockrepo.Repo) // mockRepo contains mocks of original repo layer methods generated using mockery for testing purposes
mockRepo.On("FunctionOne")
mockRepo.On("FunctionTwo")
ms.Repo = mockRepo
op := ms.MyFunction(test.input)
assert.Equal(t, test.Output, op)
})
}
} // Please keep in mind that this is not my actual code, but just a basic structure.
All tests are successful. But when executing the command go test -v, I saw multiple places in the code where the program panicked and gave invalid memory address or nil pointer dereference. I checked the code in debug mode and realized that the issue is with impl.GoRoutineWaitgroup.Add(1) in method validateMyFunction and when I commented out go validateMyFunction(a,b) and ran tests again, there were no panics in the logs. So How do I solve this issue? How to handle unit tests of functions where we start a goroutine from inside ( as in this case )?
You need initialize value to GoRoutineWaitgroup field.
ms := &Service{GoRoutineWaitgroup: &sync.WaitGroup{}}
Or remove pointer from definition
type Service struct {
Repo repo
GoRoutineWaitgroup sync.WaitGroup
}
Also I do not see waiting for Wait Group in your code. Something like ms.GoRoutineWaitgroup.Wait() and you need to move impl.GoRoutineWaitgroup.Add(1) to MyFunction from validateMyFunction otherwise the code in validateMyFunction will not be called
It is important to me to be able to assert how many times a fake / mocked method is called in my tests and I'm wondering what is the best way to do this without using something like testify. In my case, the call to the mocked method is the result of some recursive call.
Lets say I have table driven tests with various animals, I want to assert that Hello is actually called for some tests but not for others. In some cases, it should be called more than once for given test (iterating over a slice).
Is it appropriate to just add a counter and make an assertion on that in my table driven test? It seems to me like maybe there is a better way to do this.
If I do add a counter to the hello method... where is it appropriate to deal with and check this. In the fake method itself or in the test etc?
type fakeFarmService struct {
abc.someFarmServiceInterface
}
func (f *fakeFarmService) Hello(ctx context.Context, in *abc.FarmRequest) (*abc.FarmResponse, error) {
if in.GetAnimal() == Monkey {
return &abc.HelloResponse{}, nil
}
return nil, errors.New("an error")
}
I've used the approach of counter on the struct and then asserting it inside the package level unit test multiple times in the past. Still, it's probably only until the level of package, when you would like to test such an internal assertions. I believe it's an accepted way of doing this in Go. Just be careful about properly synchronizing the access to the counter, if you decide to use a global variable or run the tests concurrently.
package main
import (
"fmt"
"sync"
"testing"
)
type fakeable interface {
Hello()
}
type fakeFarmService struct {
mu sync.Mutex
counter int
}
func (f *fakeFarmService) Hello() {
f.mu.Lock()
f.counter++
f.mu.Unlock()
}
func helloCaller(callee fakeable) {
callee.Hello()
}
func TestCallingTheHello(t *testing.T) {
fakeSvc := &fakeFarmService{}
helloCaller(fakeSvc)
helloCaller(fakeSvc)
// we expect that Hello method of fakeable was called 2 times
fakeSvc.mu.Lock()
defer fakeSvc.mu.Unlock()
if c := fakeSvc.counter; c != 2 {
t.Errorf("unexpected call count, want 2, got %d", c)
}
}
func main() {
TestCallingTheHello(&testing.T{})
}
https://play.golang.org/p/RXKuLKIZwc (test error won't work inside the playground)
Some good material on advanced testing in Go
Testing Techniques by Andrew Gerrand
NewStore TechTalk - Advanced Testing with Go by Mitchell Hashimoto
I have a function which is getting called inside other function.
send_api.go
function *send_api*(client *http.Client,url string) map[string]string,error {
//send api request and parse the response and return the dict
return dictmap
for eg:{apple fruit}
}
Then this function is getting called in main() function
func *main()*{
getmap :=send_api(client *http.Client,"test.com")
}
good.go
func *get_dict_key*(key string) string,error {
value,ok := get_map[key]
if !ok {
return fmt.Errorf("value is nil")
}
return value ,nil
}
function *good*(client *http.client, key string) {
//get a dictionary value
dcmap,err := get_dict_key("apple")
if err != nil {
panic(err)
}
value := dcmap[key]
//use the value to do other processing
}
unit_test
func Test_good(t *testing.T) {
Convey("AND quadra and conusl dcs are mapped",t, func() {
mockResponses := send mock GET request to the URL and receive a response{"apple":"fruit"}
}
server, client := tools.TestClientServer(&mockResponses)
defer server.Close()
getMap := send_api(client.HTTPClient, "http://test")
//At this point getMAP has value {'apple' 'fruit'}
**q1.How to pass getMap value inside this get_dict_fkey function during testing?**
value := get_dict_key("apple")
good(client,"apple") #error:(value is nil)
Q1. **q1.How to pass getMap value inside this get_dict_function during testing?*
Any pointer would be helpful?
Assuming you are facing difficulty to mock http.Client, I would like to suggest following options.
1. Refactor the code
You need to refactor the code in such a way that you can pass the mockable dependencies to function that you would like to test.
For example,
Refactor func send_api(client *http.Client,url string) map[string]string,error so that it does api request and getting/parsing data, but call another function from it, which does the further processing (that actually you would like to test and not the http.Client part).
But, with this approach, you may not be able to test end to end flow. But you can test those functions separately.
2. Mock http.Client
Again, you may need to refactor your code. Some related article can be found here
Update: Recommending to watch justforfunc #16: unit testing HTTP servers
I'm puzzled with dependencies. I want to be able to replace some function calls with mock ones. Here's a snippet of my code:
func get_page(url string) string {
get_dl_slot(url)
defer free_dl_slot(url)
resp, err := http.Get(url)
if err != nil { return "" }
defer resp.Body.Close()
contents, err := ioutil.ReadAll(resp.Body)
if err != nil { return "" }
return string(contents)
}
func downloader() {
dl_slots = make(chan bool, DL_SLOT_AMOUNT) // Init the download slot semaphore
content := get_page(BASE_URL)
links_regexp := regexp.MustCompile(LIST_LINK_REGEXP)
matches := links_regexp.FindAllStringSubmatch(content, -1)
for _, match := range matches{
go serie_dl(match[1], match[2])
}
}
I'd like to be able to test downloader() without actually getting a page through http - i.e. by mocking either get_page (easier since it returns just the page content as a string) or http.Get().
I found this thread which seems to be about a similar problem. Julian Phillips presents his library, Withmock as a solution, but I'm unable to get it to work. Here's the relevant parts of my testing code, which is largely cargo cult code to me, to be honest:
import (
"testing"
"net/http" // mock
"code.google.com/p/gomock"
)
...
func TestDownloader (t *testing.T) {
ctrl := gomock.NewController()
defer ctrl.Finish()
http.MOCK().SetController(ctrl)
http.EXPECT().Get(BASE_URL)
downloader()
// The rest to be written
}
The test output is following:
ERROR: Failed to install '_et/http': exit status 1 output: can't load
package: package _et/http: found packages http (chunked.go) and main
(main_mock.go) in
/var/folders/z9/ql_yn5h550s6shtb9c5sggj40000gn/T/withmock570825607/path/src/_et/http
Is the Withmock a solution to my testing problem? What should I do to get it to work?
Personally, I don't use gomock (or any mocking framework for that matter; mocking in Go is very easy without it). I would either pass a dependency to the downloader() function as a parameter, or I would make downloader() a method on a type, and the type can hold the get_page dependency:
Method 1: Pass get_page() as a parameter of downloader()
type PageGetter func(url string) string
func downloader(pageGetterFunc PageGetter) {
// ...
content := pageGetterFunc(BASE_URL)
// ...
}
Main:
func get_page(url string) string { /* ... */ }
func main() {
downloader(get_page)
}
Test:
func mock_get_page(url string) string {
// mock your 'get_page()' function here
}
func TestDownloader(t *testing.T) {
downloader(mock_get_page)
}
Method2: Make download() a method of a type Downloader:
If you don't want to pass the dependency as a parameter, you could also make get_page() a member of a type, and make download() a method of that type, which can then use get_page:
type PageGetter func(url string) string
type Downloader struct {
get_page PageGetter
}
func NewDownloader(pg PageGetter) *Downloader {
return &Downloader{get_page: pg}
}
func (d *Downloader) download() {
//...
content := d.get_page(BASE_URL)
//...
}
Main:
func get_page(url string) string { /* ... */ }
func main() {
d := NewDownloader(get_page)
d.download()
}
Test:
func mock_get_page(url string) string {
// mock your 'get_page()' function here
}
func TestDownloader() {
d := NewDownloader(mock_get_page)
d.download()
}
If you change your function definition to use a variable instead:
var get_page = func(url string) string {
...
}
You can override it in your tests:
func TestDownloader(t *testing.T) {
get_page = func(url string) string {
if url != "expected" {
t.Fatal("good message")
}
return "something"
}
downloader()
}
Careful though, your other tests might fail if they test the functionality of the function you override!
The Go authors use this pattern in the Go standard library to insert test hooks into code to make things easier to test:
https://golang.org/src/net/hook.go
https://golang.org/src/net/dial.go#L248
https://golang.org/src/net/dial_test.go#L701
I'm using a slightly different approach where public struct methods implement interfaces but their logic is limited to just wrapping private (unexported) functions which take those interfaces as parameters. This gives you the granularity you would need to mock virtually any dependency and yet have a clean API to use from outside your test suite.
To understand this it is imperative to understand that you have access to the unexported methods in your test case (i.e. from within your _test.go files) so you test those instead of testing the exported ones which have no logic inside beside wrapping.
To summarize: test the unexported functions instead of testing the exported ones!
Let's make an example. Say that we have a Slack API struct which has two methods:
the SendMessage method which sends an HTTP request to a Slack webhook
the SendDataSynchronously method which given a slice of strings iterates over them and calls SendMessage for every iteration
So in order to test SendDataSynchronously without making an HTTP request each time we would have to mock SendMessage, right?
package main
import (
"fmt"
)
// URI interface
type URI interface {
GetURL() string
}
// MessageSender interface
type MessageSender interface {
SendMessage(message string) error
}
// This one is the "object" that our users will call to use this package functionalities
type API struct {
baseURL string
endpoint string
}
// Here we make API implement implicitly the URI interface
func (api *API) GetURL() string {
return api.baseURL + api.endpoint
}
// Here we make API implement implicitly the MessageSender interface
// Again we're just WRAPPING the sendMessage function here, nothing fancy
func (api *API) SendMessage(message string) error {
return sendMessage(api, message)
}
// We want to test this method but it calls SendMessage which makes a real HTTP request!
// Again we're just WRAPPING the sendDataSynchronously function here, nothing fancy
func (api *API) SendDataSynchronously(data []string) error {
return sendDataSynchronously(api, data)
}
// this would make a real HTTP request
func sendMessage(uri URI, message string) error {
fmt.Println("This function won't get called because we will mock it")
return nil
}
// this is the function we want to test :)
func sendDataSynchronously(sender MessageSender, data []string) error {
for _, text := range data {
err := sender.SendMessage(text)
if err != nil {
return err
}
}
return nil
}
// TEST CASE BELOW
// Here's our mock which just contains some variables that will be filled for running assertions on them later on
type mockedSender struct {
err error
messages []string
}
// We make our mock implement the MessageSender interface so we can test sendDataSynchronously
func (sender *mockedSender) SendMessage(message string) error {
// let's store all received messages for later assertions
sender.messages = append(sender.messages, message)
return sender.err // return error for later assertions
}
func TestSendsAllMessagesSynchronously() {
mockedMessages := make([]string, 0)
sender := mockedSender{nil, mockedMessages}
messagesToSend := []string{"one", "two", "three"}
err := sendDataSynchronously(&sender, messagesToSend)
if err == nil {
fmt.Println("All good here we expect the error to be nil:", err)
}
expectedMessages := fmt.Sprintf("%v", messagesToSend)
actualMessages := fmt.Sprintf("%v", sender.messages)
if expectedMessages == actualMessages {
fmt.Println("Actual messages are as expected:", actualMessages)
}
}
func main() {
TestSendsAllMessagesSynchronously()
}
What I like about this approach is that by looking at the unexported methods you can clearly see what the dependencies are. At the same time the API that you export is a lot cleaner and with less parameters to pass along since the true dependency here is just the parent receiver which is implementing all those interfaces itself. Yet every function is potentially depending only on one part of it (one, maybe two interfaces) which makes refactors a lot easier. It's nice to see how your code is really coupled just by looking at the functions signatures, I think it makes a powerful tool against smelling code.
To make things easy I put everything into one file to allow you to run the code in the playground here but I suggest you also check out the full example on GitHub, here is the slack.go file and here the slack_test.go.
And here the whole thing.
I would do something like,
Main
var getPage = get_page
func get_page (...
func downloader() {
dl_slots = make(chan bool, DL_SLOT_AMOUNT) // Init the download slot semaphore
content := getPage(BASE_URL)
links_regexp := regexp.MustCompile(LIST_LINK_REGEXP)
matches := links_regexp.FindAllStringSubmatch(content, -1)
for _, match := range matches{
go serie_dl(match[1], match[2])
}
}
Test
func TestDownloader (t *testing.T) {
origGetPage := getPage
getPage = mock_get_page
defer func() {getPage = origGatePage}()
// The rest to be written
}
// define mock_get_page and rest of the codes
func mock_get_page (....
And I would avoid _ in golang. Better use camelCase
the simplest way is to set function into a global variable and before test set your custom method
// package base36
func GenerateRandomString(length int) string {
// your real code
}
// package teamManager
var RandomStringGenerator = base36.GenerateRandomString
func (m *TeamManagerService) CreateTeam(ctx context.Context) {
// we are using the global variable
code = RandomStringGenerator(5)
// your application logic
return nil
}
and in your test, you must first mock that global variable
teamManager.RandomStringGenerator = func(length int) string {
return "some string"
}
service := &teamManager.TeamManagerService{}
service.CreateTeam(context.Background())
// now when we call any method that user teamManager.RandomStringGenerator, it will call our mocked method
another way is to pass RandomStringGenerator as a dependency and store it inside TeamManagerService and use it like this:
// package teamManager
type TeamManagerService struct {
RandomStringGenerator func(length int) string
}
// in this way you don't need to change your main/where this code is used
func NewTeamManagerService() *TeamManagerService {
return &TeamManagerService{RandomStringGenerator: base36.GenerateRandomString}
}
func (m *TeamManagerService) CreateTeam(ctx context.Context) {
// we are using the struct field variable
code = m.RandomStringGenerator(5)
// your application logic
return nil
}
and in your test, you can use your own custom function
myGenerator = func(length int) string {
return "some string"
}
service := &teamManager.TeamManagerService{RandomStringGenerator: myGenerator}
service.CreateTeam(context.Background())
you are using testify like me :D you can do this
// this is the mock version of the base36 file
package base36_mock
import "github.com/stretchr/testify/mock"
var Mock = mock.Mock{}
func GenerateRandomString(length int) string {
args := Mock.Called(length)
return args.String(0)
}
and in your test, you can use your own custom function
base36_mock.Mock.On("GenerateRandomString", 5).Return("my expmle code for this test").Once()
service := &teamManager.TeamManagerService{RandomStringGenerator: base36_mock.GenerateRandomString}
service.CreateTeam(context.Background())
Warning: This might inflate executable file size a little bit and cost a little runtime performance. IMO, this would be better if golang has such feature like macro or function decorator.
If you want to mock functions without changing its API, the easiest way is to change the implementation a little bit:
func getPage(url string) string {
if GetPageMock != nil {
return GetPageMock()
}
// getPage real implementation goes here!
}
func downloader() {
if GetPageMock != nil {
return GetPageMock()
}
// getPage real implementation goes here!
}
var GetPageMock func(url string) string = nil
var DownloaderMock func() = nil
This way we can actually mock one function out of the others. For more convenient we can provide such mocking boilerplate:
// download.go
func getPage(url string) string {
if m.GetPageMock != nil {
return m.GetPageMock()
}
// getPage real implementation goes here!
}
func downloader() {
if m.GetPageMock != nil {
return m.GetPageMock()
}
// getPage real implementation goes here!
}
type MockHandler struct {
GetPage func(url string) string
Downloader func()
}
var m *MockHandler = new(MockHandler)
func Mock(handler *MockHandler) {
m = handler
}
In test file:
// download_test.go
func GetPageMock(url string) string {
// ...
}
func TestDownloader(t *testing.T) {
Mock(&MockHandler{
GetPage: GetPageMock,
})
// Test implementation goes here!
Mock(new(MockHandler)) // Reset mocked functions
}
I have been in similar spot. I was trying to write unitTest for a function which had numerous clients calling it. let me propose 2 options that I explored. one of which is already discussed in this thread, I will regardless repeat it for the sake of people searching.
Method 1: Declaring function you wanna mock as a Global variable
one option is declaring a global variable (has some pit falls).
eg:
package abc
var getFunction func(s string) (string, error) := http.Get
func get_page(url string) string {
....
resp, err := getFunction(url)
....
}
func downloader() {
.....
}
and the test func will be as follows:
package abc
func testFunction(t *testing.T) {
actualFunction := getFunction
getFunction := func(s string) (string, error) {
//mock implementation
}
defer getFunction = actualFunction
.....
//your test
......
}
NOTE: test and actual implementation are in the same package.
there are some restrictions with above method thought!
running parallel tests is not possible due to risk of race conditions.
by making function a variable, we are inducing a small risk of reference getting modified by future developers working in same package.
Method 2: Creating a wrapped function
another method is to pass along the methods you want to mock as arguments to the function to enable testability. In my case, I already had numerous clients calling this method and thus, I wanted to avoid violating the existing contracts. so, I ended up creating a wrapped function.
eg:
package abc
type getOperation func(s string) (string, error)
func get_page(url string, op getOperation) string {
....
resp, err := op(url)
....
}
//contains only 2 lines of code
func downloader(get httpGet) {
op := http.Get
content := wrappedDownloader(get, op)
}
//wraps all the logic that was initially in downloader()
func wrappedDownloader(get httpGet, op getOperation) {
....
content := get_page(BASE_URL, op)
....
}
now for testing the actual logic, you will test calls to wrappedDownloader instead of Downloader and you would pass it a mocked getOperation. this is allow you to test all the business logic while not violating your API contract with current clients of the method.
Considering unit test is the domain of this question, highly recommend you to use monkey. This Package make you to mock test without changing your original source code. Compare to other answer, it's more "non-intrusive".
main
type AA struct {
//...
}
func (a *AA) OriginalFunc() {
//...
}
mock test
var a *AA
func NewFunc(a *AA) {
//...
}
monkey.PatchMethod(reflect.TypeOf(a), "OriginalFunc", NewFunc)
Bad side is:
Reminded by Dave.C, This method is unsafe. So don't use it outside of unit test.
Is non-idiomatic Go.
Good side is:
Is non-intrusive. Make you do things without changing the main code. Like Thomas said.
Make you change behavior of package (maybe provided by third party) with least code.