I come from python and I have been looking for a way to write yests in go. I have come across a few things on SO but they all seem very cumbersome and verbose for something that shpuld be needed all the time.
I am typing on mobile now, will add code later if needed...but for example...
say i have a function that calls smtp.Send somewhere in the middle. how can I easily test this function?
Say i have another one that hits some outside api (needs mocking) and then takes the response and calls something like ioutil.Readall()...how could i make my way through this test function and mock the call to the api and then pass some fake response data when Readall is called?
You can do it by using an interface. For example let's say you have an interface called Mailer:
type Mailer interface {
Send() error
}
Now you can embed a Mailer object into the function that calls the Send method.
type Processor struct {
Mailer
}
func (p *Processor) Process() {
_ = p.Mailer.Send()
}
Now in your test you can create a mock Mailer.
type mockMailer struct{}
//implement the Send on the mockMailer as you wish
p := &Processor{
Mailer: mockMailer,
}
p.Process()
when p.Process reaches the Send method it calls your mocked Send method.
Related
I am new to Golang and have been exploring but not clear about mocking in unit tests. Can anyone explain following specific questions ?
Question1: For writing unit tests in Golang, why we need to have interfaces to mock methods, why not only struct ?
Question2: Why we inject the interface in struct(where we call external method)
With struct -
type GlobalData struct {}
var (
GlobalObj = GlobalData{}
)
func (g GlobalData) GetGlobalData(a string) string{
return a
}
With interface definition-
type GlobalInterface interface {
GetGlobalData(a string) string
}
type GlobalData struct {}
var (
GlobalObj = GlobalData{}
)
func (g GlobalData) GetGlobalData(a string) string{
return a
}
Thanks
Question 1: For writing unit tests in Golang, why we need to have interfaces to mock methods, why not only struct ?
Answer: Its not mandatory
Question 2: Why we inject the interface in struct(where we call external method)
Answer: Because, it helps you to replace the actual function call (that might trigger some out of scope actions as a part of unit test , such as database call, some API call etc) by injecting a MockStruct (which will be implementing the same interface that is there in the actual code). Polymorphism in simple words.
So, you create a MockStruct and define your own mockMethods to it. As polymorphism, your unit test pick MockStruct without complaining. Calling actual DB or http endpoints do not come under unit testing.
Just for reference, I can point you to one of my github codebase where I wrote a small test case for a file. As you can see I mocked :
GuestCartHandler interface , that allowed me to not call the actual implementation
Mocked sql connection using "github.com/DATA-DOG/go-sqlmock" package. This helped me to avoid establishing actual db client (so, no dependency of database while unit testing)
Let me know if you get the idea conceptually or do you need some more clarification.
If you have methods on types in package user let's say, ex.
package user
type User struct {
name string
}
func (u *User) GetUserProfile() UserProfile{}
And now on import in catalog package :
package catalog
import user
func getUserCatalog(user user.User) []catalog {
user.GetUserProfile()
}
Now to test getUserCatalog method there are 2 ways:
1. var getUserProfileFunc = user.GetUserProfile
using this approach mock can be easily passed at test run time like:
getUserProfile = func() UserProfile {
return fakeUserProfile
}
this is the easiest way to test it.
Now there is another way using interface, in package user add an interface like
type UserInterface interface {
GetUserProfile() UserProfile
}
if User package is a library on which you don't have control then create your own interface, type and use this.
In this case testing in catalog package will become like:
because now methods will be invoked from UserInterface type not from UserType, hence while testing :
UserInterface = fakeUserStruct
and follow below steps
//1. define type of func to return
type typeGetUserProfile func() UserProfile
//2. create a var to return
var mockedGetUserProfile typeGetUserProfile
//3. create a type
type FakeUser struct{}
//4. implement method interface
func (user *FakeUserStruct) GetUserProfile() UserProfile{
return mockedGetUserProfile
}
now when running test :
mockerGetUserProfile = func() UserProfile {
return fakeUserProfile
}
There is mock library which helps in creating boilerplate code for mocking. Check this https://github.com/stretchr/testify
There are many other mock library, but I had used this one, this was really cool.
I hope this helps.
if not please let me know, i'll give some example code and push it to Github.
Also please check https://levelup.gitconnected.com/utilizing-the-power-of-interfaces-when-mocking-and-testing-external-apis-in-golang-1178b0db5a32
I was looking at the documentation at: https://pub.dartlang.org/packages/mockito and was trying to understand it more. It seems that in the examples, the function stubs were accepting strings, but was kind of confused as to how I was going to implement my Mocked Services.
I was curious how I would do it. The services I have is pretty simple and straight forward.
class Group{}
class GroupService {}
class MockGroupService extends Mock implements GroupService {}
final mockProviders = [new Provider(MockGroupService, useExisting: GroupService];
So you can see I am using Angular dart.
I was creating a sample group in my Test file.
group("service tests", (){
MockGroupService _mock;
testBed.addProviders([mockProviders]);
setUp(() async {
fixture = await testBed.create();
_mock = new MockGroupService();
//This is where I was going to create some stubbs for the methods
when(_mock.add()).thenReturn((){
return null; //return the object.
});
//create additional when statements for edit, delete, etc.
});
});
So what i was thinking is that there would be an argument passed into add (or 2).... how would I properly code that in the when statement, and how do those 2 arguments reflect in the then statement?
Essentially, I was wanting to do a test with a complex class.. and pass it into add. Then it would just process it accordingly and return it.
Do i pass into the arguments something akin to: (using pseudocode)
when(_mock.add(argThat(hasType(Group)))).thenReturn((Group arg)=> arg);
or something similar? hasType isnt function, so im not 100% sure how to approach this design. Ideally, Im trying create the Group in the test, and then pass it into the add function accordingly. It just seems that the examples were showing Strings.
Yes mockito allows objects to be passed you can see examples in the test.
It is a bit hard to follow but you can see here that it uses deep equality to check if arguments are equal if no matchers are specified.
The second part of your question is a bit more complex. If you want to use the values that were passed into your mock as part of your response then you need to use thenAnswer. It provides you with an Invocation of what was just called. From that object you can get and return any arguments that were used in the method call.
So for your add example if you know what is being passing in and have complete access to it I would write:
Group a = new Group();
when(_mock.add(a)).thenReturn(a);
If the Group object is being created by something else I would write:
when(_mock.add(argThat(new isInstanceOf<Group>()))
.thenAnswer((invocation)=>invocation.positionalArguments[0]);
Or if you don't really care about checking for the type. Depending on what checks you are using for your test the type might already be checked for you.
when(_mock.add(any)).thenAnswer(
(invocation)=>invocation.positionalArguments[0]);
Or if you are using Dart 2.0:
when(_mock.add(typed(any))).thenAnswer(
(invocation)=>invocation.positionalArguments[0]);
I'm studying the outyet example project from https://github.com/golang/example/tree/master/outyet. The test file does not cover the case where http.Head(url) returns an error. I would like to extend the unit tests to cover the if statement where the error is logged (https://github.com/golang/example/blob/master/outyet/main.go#L100). I would like to mock http.Head(), but I'm not sure how to do this. How can this be done?
The http.Head function simply calls the Head method on the default HTTP client (exposed as http.DefaultClient). By replacing the default client within your test, you can change the behaviour of these standard library functions.
In particular, you will want a client that sets a custom transport (any object implementing the http.RoundTripper interface). Something like the following:
type testTransport struct{}
func (t testTransport) RoundTrip(request *http.Request) (*http.Response, error) {
# Check expectations on request, and return an appropriate response
}
...
savedClient := http.DefaultClient
http.DefaultClient = &http.Client{
Transport: testTransport{},
}
# perform tests that call http.Head, http.Get, etc
http.DefaultClient = savedClient
You could also use this technique to mock network errors by returning an error from your transport rather than an HTTP response.
Is there a way to execute test cases in GoLang in a pre-defined order.
P.S: I am writing test cases for life cycle of a event. So I have different api's for all the CURD operations. I want to run these test cases in a particular order as only if an event is created it can be destroyed.
Also can I get some value from one test case and pass it as input to another. (example:- To test the delete event api, I need a event_id which i get when I call create_event test case)
I am new to GoLang, can someone please guide me through.
Thanks in advance
The only way to do it is to encapsulate all your tests into one test function, that calls sub-functions in the right order and with the right context, and pass the testing.T pointer to each so they can fail. The down-side is that they will all appear as one test. But in fact that is the case - tests are stateless as far as the testing framework is concerned, and each function is a separate test case.
Note that although the tests may run in the order they are written in, I found no documentation stating that this is actually a contract of some sort. So even though you can write them in order and keep the state as external global variables - that's not recommended.
The only flexibility the framework gives you since go 1.4 is the TestMain method that lets you run before/after steps, or setup/teardown:
func TestMain(m *testing.M) {
if err := setUp(); err != nil {
panic(err)
}
rc := m.Run()
tearDown()
os.Exit(rc)
}
But that won't give you what you want. The only way to do that safely is to do something like:
// this is the whole stateful sequence of tests - to the testing framework it's just one case
func TestWrapper(t *testing.T) {
// let's say you pass context as some containing struct
ctx := new(context)
test1(t, ctx)
test2(t, ctx)
...
}
// this holds context between methods
type context struct {
eventId string
}
func test1(t *testing.T, c *context) {
// do your thing, and you can manipulate the context
c.eventId = "something"
}
func test2(t *testing.T, c *context) {
// do your thing, and you can manipulate the context
doSomethingWith(c.eventId)
}
First up, where my knowledge is at:
Unit Tests are those which test a small piece of code (single methods, mostly).
Integration Tests are those which test the interaction between multiple areas of code (which hopefully already have their own Unit Tests). Sometimes, parts of the code under test requires other code to act in a particular way. This is where Mocks & Stubs come in. So, we mock/stub out a part of the code to perform very specifically. This allows our Integration Test to run predictably without side effects.
All tests should be able to be run stand-alone without data sharing. If data sharing is necessary, this is a sign the system isn't decoupled enough.
Next up, the situation I am facing:
When interacting with an external API (specifically, a RESTful API that will modify live data with a POST request), I understand we can (should?) mock out the interaction with that API (more eloquently stated in this answer) for an Integration Test. I also understand we can Unit Test the individual components of interacting with that API (constructing the request, parsing the result, throwing errors, etc). What I don't get is how to actually go about this.
So, finally: My question(s).
How do I test my interaction with an external API that has side effects?
A perfect example is Google's Content API for shopping. To be able to perform the task at hand, it requires a decent amount of prep work, then performing the actual request, then analysing the return value. Some of this is without any 'sandbox' environment.
The code to do this generally has quite a few layers of abstraction, something like:
<?php
class Request
{
public function setUrl(..){ /* ... */ }
public function setData(..){ /* ... */ }
public function setHeaders(..){ /* ... */ }
public function execute(..){
// Do some CURL request or some-such
}
public function wasSuccessful(){
// some test to see if the CURL request was successful
}
}
class GoogleAPIRequest
{
private $request;
abstract protected function getUrl();
abstract protected function getData();
public function __construct() {
$this->request = new Request();
$this->request->setUrl($this->getUrl());
$this->request->setData($this->getData());
$this->request->setHeaders($this->getHeaders());
}
public function doRequest() {
$this->request->execute();
}
public function wasSuccessful() {
return ($this->request->wasSuccessful() && $this->parseResult());
}
private function parseResult() {
// return false when result can't be parsed
}
protected function getHeaders() {
// return some GoogleAPI specific headers
}
}
class CreateSubAccountRequest extends GoogleAPIRequest
{
private $dataObject;
public function __construct($dataObject) {
parent::__construct();
$this->dataObject = $dataObject;
}
protected function getUrl() {
return "http://...";
}
protected function getData() {
return $this->dataObject->getSomeValue();
}
}
class aTest
{
public function testTheRequest() {
$dataObject = getSomeDataObject(..);
$request = new CreateSubAccountRequest($dataObject);
$request->doRequest();
$this->assertTrue($request->wasSuccessful());
}
}
?>
Note: This is a PHP5 / PHPUnit example
Given that testTheRequest is the method called by the test suite, the example will execute a live request.
Now, this live request will (hopefully, provided everything went well) do a POST request that has the side effect of altering live data.
Is this acceptable? What alternatives do I have? I can't see a way to mock out the Request object for the test. And even if I did, it would mean setting up results / entry points for every possible code path that Google's API accepts (which in this case would have to be found by trial and error), but would allow me the use of fixtures.
A further extension is when certain requests rely on certain data being Live already. Using the Google Content API as an example again, to add a Data Feed to a Sub Account, the Sub Account must already exist.
One approach I can think of is the following steps;
In testCreateAccount
Create a sub-account
Assert the sub-account was created
Delete the sub-account
Have testCreateDataFeed depend on testCreateAccount not having any errors
In testCreateDataFeed, create a new account
Create the data feed
Assert the data feed was created
Delete the data feed
Delete the sub-account
This then raises the further question; how do I test the deletion of accounts / data feeds? testCreateDataFeed feels dirty to me - What if creating the data feed fails? The test fails, therefore the sub-account is never deleted... I can't test deletion without creation, so do I write another test (testDeleteAccount) that relies on testCreateAccount before creating then deleting an account of its own (since data shouldn't be shared between tests).
In Summary
How do I test interacting with an external API that effects live data?
How can I mock / stub objects in an Integration test when they're hidden behind layers of abstraction?
What do I do when a test fails and the live data is left in an inconsistent state?
How in code do I actually go about doing all this?
Related:
How can mocking external services improve unit tests?
Writing unit tests for a REST-ful API
This is more an additional answer to the one already given:
Looking through your code, the class GoogleAPIRequest has a hard-encoded dependency of class Request. This prevents you from testing it independently from the request class, so you can't mock the request.
You need to make the request injectable, so you can change it to a mock while testing. That done, no real API HTTP requests are send, the live data is not changed and you can test much quicker.
I've recently had to update a library because the api it connects to was updated.
My knowledge isn't enough to explain in detail, but i learnt a great deal from looking at the code. https://github.com/gridiron-guru/FantasyDataAPI
You can submit a request as you would normally to the api and then save that response as a json file, you can then use that as a mock.
Have a look at the tests in this library which connects to an api using Guzzle.
It mocks responses from the api, there's a good deal of information in the docs on how the testing works it might give you an idea of how to go about it.
but basically you do a manual call to the api along with any parameters you need, and save the response as a json file.
When you write your test for the api call, send along the same parameters and get it to load in the mock rather than using the live api, you can then test the data in the mock you created contains the expected values.
My Updated version of the api in question can be found here.
Updated Repo
One of the ways to test out external APIs is as you mentioned, by creating a mock and working against that with the behavior hard coded as you have understood it.
Sometimes people refer to this type of testing as "contract based" testing, where you can write tests against the API based on the behavior you have observed and coded against, and when those tests start failing, the "contract is broken". If they are simple REST based tests using dummy data you can also provide them to the external provider to run so they can discover where/when they might be changing the API enough that it should be a new version or produce a warning about not being backwards compatible.
Ref: https://www.thoughtworks.com/radar/techniques/consumer-driven-contract-testing