Returning a Mock from a package function - go

I'm fairly new to Go and I'm having some issues with writing tests, specifically mocking the response of a package function.
I'm writing an wrapper lib for github.com/go-redis/redis. At the moment it only really has better errors for failures, but it will be expanded with statsd tracking further down the line, but I digress...
I have the following go package that I have created
package myredis
import (
"time"
"github.com/go-redis/redis"
errors "github.com/pkg/errors"
)
var newRedisClient = redis.NewClient
// Options - My Redis Connection Options
type Options struct {
*redis.Options
DefaultLifetime time.Duration
}
// MyRedis - My Redis Type
type MyRedis struct {
options Options
client *redis.Client
}
// Connect - Connects to the Redis Server. Returns an error on failure
func (r *MyRedis) Connect() error {
r.client = newRedisClient(&redis.Options{
Addr: r.options.Addr,
Password: r.options.Password,
DB: r.options.DB,
})
_, err := r.client.Ping().Result()
if err != nil {
return errors.Wrap(err, "myredis")
}
return nil
}
My problem is that I want redis.NewClient to return a mock. This is the test code that I wrote, but it's not working:
package myredis
import (
"testing"
"github.com/go-redis/redis"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/mock"
)
type redisStatusCmdMock struct {
mock.Mock
}
func (m *redisStatusCmdMock) Result() (string, error) {
args := m.Called()
return args.Get(0).(string), args.Error(1)
}
type redisClientMock struct {
mock.Mock
}
func (m *redisClientMock) Ping() redis.StatusCmd {
args := m.Called()
return args.Get(0).(redis.StatusCmd)
}
func TestConnect(t *testing.T) {
assert := assert.New(t)
old := newRedisClient
defer func() { newRedisClient = old }()
newRedisClient = func(options *redis.Options) *redis.Client {
assert.Equal("127.0.0.1:1001", options.Addr)
assert.Equal("password", options.Password)
assert.Equal(1, options.DB)
statusCmdMock := new(redisStatusCmdMock)
statusCmdMock.On("Result").Return("success", nil)
clientMock := new(redisClientMock)
clientMock.On("Ping").Return(statusCmdMock)
return clientMock
}
options := Options{}
options.Addr = "127.0.0.1:1001"
options.Password = "password"
options.DB = 1
r := MyRedis{options: options}
result, err := r.Connect()
assert.Equal("success", result)
assert.Equal(nil, err)
}
I get the following error: cannot use clientMock (type *redisClientMock) as type *redis.Client in return argument. I think I read that I need to mock all the functions of redis.Client in order to be able to use it as a mock in this case, but is that really the case? That seems like it's overkill and I should be able to do this in some way. How do I go about getting this test to work, or do I need to restructure my code so that it's easier to write the test?

redis.Client is a struct type and in Go struct types are simply not mockable. However interfaces in Go are mockable, so what you can do is to define your own "newredisclient" func that instead of returning a struct returns an interface. And since interfaces in Go are satisfied implicitly you can define your interface such that it will be implemented by redis.Client out of the box.
type RedisClient interface {
Ping() redis.StatusCmd
// include any other methods that you need to use from redis
}
func NewRedisCliennt(options *redis.Options) RedisClient {
return redis.NewClient(options)
}
var newRedisClient = NewRedisClient
If you also want to mock the return value from Ping(), you need to do a bit more work.
// First define an interface that will replace the concrete redis.StatusCmd.
type RedisStatusCmd interface {
Result() (string, error)
// include any other methods that you need to use from redis.StatusCmd
}
// Have the client interface return the new RedisStatusCmd interface
// instead of the concrete redis.StatusCmd type.
type RedisClient interface {
Ping() RedisStatusCmd
// include any other methods that you need to use from redis.Client
}
Now *redis.Client does not satisfy the RedisClient interface anymore because the return type of Ping() is different. Note that it doesn't matter that the result type of redis.Client.Ping() satisfies the interface type returned by RedisClient.Ping(), what matters is that the method signatures are different and therefore their types are different.
To fix this you can define a thin wrapper that uses *redis.Client directly and also satisfies the new RedisClient interface.
type redisclient struct {
rc *redis.Client
}
func (c *redisclient) Ping() RedisStatusCmd {
return c.rc.Ping()
}
func NewRedisCliennt(options *redis.Options) RedisClient {
// here wrap the *redis.Client into *redisclient
return &redisclient{redis.NewClient(options)}
}
var newRedisClient = NewRedisClient

Related

Does Set() method of echo.Context saves the value to the underlying context.Context?

I am using Echo framework and want to pass the Go's built-in context.Context underlying echo.Context after setting some custom values.
To achieve it, I think I could first apply Set(key string, val interface{}) method of echo.Context and then extract the underlying context.Context.
Question is is it possible to do it this way? In other words, does echo.Context.Set(...) sets the value directly on the context.Context just like WithValue does? Or should I take extra steps to copy my custom entries down.
P.S. I do not want to pass echo.Context to deeper layers of my app, that's why I do not want to directly use it but get the referring context.Context
Method 1: Reimplement the echo.Context.Get and echo.Context.Set methods to manipulate the ctx.Request().Context() object.
Disadvantages: http.Request.WithContext will be called once for each Set method, and *http.Request will be copied once. See the implementation of WithContext method for details.
Method 2: Reimplement the echo.Context.Get and echo.Context.Set methods to manipulate the contextValueData2 object, and set http.Request.WithContext to a custom context.Context contextValueData2.
Disadvantages: Before go1.13, context.Context requires Type assertions. Don't implement the context.Context method. Compared with method 1, the implementation only requires WithContext once.
It is recommended to use method 1, which is clear and simple, and method 2 is complicated and not fully tested.
The example import package uses gopath, and the implementation of this feature also reflects the advantage of echo.Context as an interface.
package main
import (
"context"
"fmt"
"github.com/labstack/echo"
"github.com/labstack/echo/middleware"
"net/http"
)
func main() {
// Echo instance
e := echo.New()
// Middleware
e.Use(NewMiddlewareContextValue)
e.Use(middleware.Logger())
e.Use(middleware.Recover())
// Routes
e.GET("/", hello)
e.GET("/val", getval)
// Start server
e.Logger.Fatal(e.Start(":1323"))
}
// Handler
func hello(c echo.Context) error {
return c.String(http.StatusOK, "Hello, World!")
}
func getval(c echo.Context) error {
c.Set("111", "aa")
c.Set("222", "bb")
return c.String(http.StatusOK, fmt.Sprint(c.Request().Context()))
}
// ---------- method1 ----------
func NewMiddlewareContextValue(fn echo.HandlerFunc) echo.HandlerFunc {
return func(ctx echo.Context) error {
return fn(contextValue{ctx})
}
}
type contextValue struct {
echo.Context
}
// Get retrieves data from the context.
func (ctx contextValue) Get(key string) interface{} {
// get old context value
val := ctx.Context.Get(key)
if val != nil {
return val
}
return ctx.Request().Context().Value(key)
}
// Set saves data in the context.
func (ctx contextValue) Set(key string, val interface{}) {
ctx.SetRequest(ctx.Request().WithContext(context.WithValue(ctx.Request().Context(), key, val)))
}
// ---------- method2 ----------
func NewMiddlewareContextValue2(fn echo.HandlerFunc) echo.HandlerFunc {
return func(ctx echo.Context) error {
ctxdata := contextValueData2{
Context: ctx.Request().Context(),
}
ctx.SetRequest(ctx.Request().WithContext(ctxdata))
return fn(&contextValue2{Context: ctx, contextValueData2: ctxdata})
}
}
type contextValue2 struct {
echo.Context
contextValueData2
}
type contextValueData2 struct {
context.Context
Data map[string]interface{}
}
// Get retrieves data from the context.
func (ctx *contextValue2) Get(key string) interface{} {
// get old context value
val := ctx.Context.Get(key)
if val != nil {
return val
}
// get my data value
val, ok := ctx.contextValueData2.Data[key]
if ok {
return val
}
return ctx.contextValueData2.Context.Value(key)
}
// Set saves data in the context.
func (ctx *contextValue2) Set(key string, val interface{}) {
if ctx.Data == nil {
ctx.contextValueData2.Data = make(map[string]interface{})
}
ctx.contextValueData2.Data[key] = val
}
func (ctx contextValueData2) Value(key interface{}) interface{} {
str, ok := key.(string)
if ok {
val, ok := ctx.Data[str]
if ok {
return val
}
}
return ctx.Context.Value(key)
}

How to mock a gin.Context?

Hi I've been trying to mock a gin.Context but I have not been able to make it work
I was trying what they did in this solution but it does not work with my router this is the error I have been getting
r.POST("/urls", urlRepo.CreateUrl)
cannot use urlRepo.CreateUrl (value of type func(c controllers.Icontext)) as gin.HandlerFunc value in argument to r.POSTcompilerIncompatibleAssign
This is the interface I created to later mock and the method in which I will be testing
type Icontext interface {
BindJSON(obj interface{}) error
JSON(code int, obj interface{})
AbortWithStatus(code int)
AbortWithStatusJSON(code int, jsonObj interface{})
}
func (repository *UrlRepo) CreateUrl(c Icontext) {
var url models.Url
c.BindJSON(&url)
if !validators.IsCreateJsonCorrect(url) {
c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"error": "Error format in Short or Full"})
return
}
err := repository.reposito.CreateUrl(repository.Db, &url)
if err != nil {
c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err})
return
}
c.JSON(http.StatusOK, url)
}
Instead of
func (repository *UrlRepo) CreateUrl(c Icontext)
it was
func (repository *UrlRepo) CreateUrl(c *gin.Context)
Strictly speaking, you can't "mock" a *gin.Context in a meaningful way, because it's a struct with unexported fields and methods.
Furthermore, you can't pass to r.POST() a function whose type is not a gin.HandlerFunc, defined as func(*gin.Context). The type of your handler CreateUrl(c Icontext) simply doesn't match.
If your goal is to unit test a Gin handler, you definitely don't have to mock the *gin.Context. What you should do is to set test values into it. For that, you can simply use gin.CreateTestContext() and manually init some of it fields. More info here.
If for some other reason, your goal is to provide an alternate implementation of a functionality of *gin.Context for use inside your handler, what you can do is define your own type with your own alternative methods and embed the *gin.Context in it.
In practice:
type MyGinContext struct {
*gin.Context
}
func (m *MyGinContext) BindJSON(obj interface{}) error {
fmt.Println("my own BindJSON")
return m.Context.BindJSON(obj) // or entirely alternative implementation
}
// Using the appropriate function signature now
func (repository *UrlRepo) CreateUrl(c *gin.Context) {
myCtx := &MyGinContext{c}
var url models.Url
_ = myCtx.BindJSON(&url) // will also print "my own BindJSON"
// ...
// other gin.Context methods are promoted and available on MyGinContext
myCtx.Status(200)
}
But honestly I'm not sure why you would want to override some methods of the *gin.Context. If you want to provide different binding logic, or even different rendering, you can implement the interfaces that are already exposed by the library. For example:
Implement a binding:
c.ShouldBindWith() takes as second parameter an interface binding.Binding which you can implement:
type MyBinder struct {
}
func (m *MyBinder) Name() string {
return "foo"
}
func (m *MyBinder) Bind(*http.Request, interface{}) error {
// stuff
return nil
}
func MyHandler(c *gin.Context) {
var foo struct{/*fields*/}
c.ShouldBindWith(&foo, &MyBinder{})
}
Implement a renderer:
type MyRenderer struct {
}
type Render interface {
func (m *MyRenderer) Render(http.ResponseWriter) error {
// ...
return nil
}
func (m *MyRenderer) WriteContentType(w http.ResponseWriter) {
header := w.Header()
if val := header["Content-Type"]; len(val) == 0 {
header["Content-Type"] = "application/foo+bar"
}
}
func MyHandler(c *gin.Context) {
c.Render(200, &MyRenderer{})
}
if you are using gin-gonic as your http router, the param for your entry point should be a *gin.Context.
So, for instance, you should be replacing this:
func (repository *UrlRepo) CreateUrl(c Icontext) {
With this
func (repository *UrlRepo) CreateUrl(c *gin.Context) {
This way you should be able to use a mock gin context as a parameter for your unit test

Can I mock a function with pointer parameter which need to be used

Let's say we have a library provide a function Double to double the integer, we use pointer i to get the result value not by return:
package api
type Action interface {
Double(i *int) error
}
type NUM struct{}
func (n NUM) Double(i *int) error {
*i *= 2
return nil
}
in our main function we use this library to do our task. like this:
package app
import (
"fmt"
"github.com/hotsnow/api"
)
func main() {
j := job{a: &api.NUM{}}
d := j.task(3)
fmt.Println(3, d)
}
type job struct {
a api.Action
}
// double me
func (j job) task(i int) int {
j.a.Double(&i)
return i
}
Now we need to test the task() function, how can we get the pointer return bye mock the Double function?
Here is the test:
package app
import (
"github.com/golang/mock/gomock"
"github.com/hotsnow/mocks"
"testing"
)
func TestReq(t *testing.T) {
ctrl := gomock.NewController(t)
defer ctrl.Finish()
m := mocks.NewMockAction(ctrl)
m.EXPECT().Double(gomock.Any()).Return(nil)
j := job{a: m}
got := j.task(3)
if got != 6 {
t.Errorf("got = %#v; want 6", got)
}
}
The code here: https://github.com/hotsnow/mock.git (stackoverflow branch)
you can use gomock setarg function for this
yourPackage.EXPECT().insert(&pointer).SetArg(0, newPointer)
You can achieve this with the provided Eq() matcher, which internally calls reflect.DeepEqual() on the expected and actual values; as per the documentation for this method:
Pointer values are deeply equal if they are equal using Go's == operator or if they point to deeply equal values.
Say we have a function that depends upon an interface method that takes a pointer parameter:
package resource
type ServiceRequest struct {
Name string
Owner *string // this is a pointer so it can be omitted with `nil`
}
type Model struct {
// resource model...
}
type ResourceService interface {
Fetch(req *ServiceRequest) (Model, error)
}
type getResourceHandler struct {
resourceService ResourceService
}
type GetResourceEvent struct {
Resource string
Owner *string
}
func NewResourceHandler(resourceService ResourceService) *getResourceHandler {
return &getResourceHandler{resourceService}
}
func (h *getResourceHandler) Handle(event GetResourceEvent) (Model, error) {
return h.resourceService.Fetch(&ServiceRequest{event.Resource, event.Owner})
}
We can use the Eq() matcher when setting up the expectation against our generated mock of the ResourceService interface:
package test
import (
"testing"
"github.com/golang/mock/gomock"
"github.com/stretchr/testify/assert"
"github.com/org/repo/internal/mock"
"github.com/org/repo/internal/resource"
)
func optionalString(str string) *string {
return &str
}
func Test_GetResourceHandler_ReturnsResultFromService(t *testing.T) {
resourceName := "my-resource"
owner := optionalString("Joe Bloggs")
resourceReq := &resource.ServiceRequest{resourceName, owner}
event := resource.GetResourceEvent{resourceName, owner}
model := resource.Model{ /* fields here... */ }
ctrl := gomock.NewController(t)
mockResourceService := mock.NewMockResourceService(ctrl)
handler := resource.NewResourceHandler(mockResourceService)
mockResourceService.EXPECT().Fetch(gomock.Eq(resourceReq)).Return(model, nil)
res, err := handler.Handle(event)
assert.Nil(t, err)
assert.Equal(t, model, res)
}
If you change the contents of the service request in either the test or the unit under test, you'll see that the test no longer passes. Otherwise, it will pass in spite of the test and the unit under test having their own respective pointers to separate ServiceRequest{} values.
It seems you don't have to use gomock to test the task method.
Since you have an interface, why not just create a mock implementation of the interface, for example:
type dummy struct{
callCount int
}
func (d *dummy) Double(i *int) error {
d.callCount++
return nil
}
d := dummy{}
j := job{a: &d}
got := j.task(3)
if d.callCount != 1 {
// XXX
}

Typecasting one function into another in golang

I have the following code:
package vault
type Client interface {
GetHealth() error
}
func (c DefaultClient) GetHealth () error {
resp := &VaultHealthResponse{}
err := c.get(resp, "/v1/sys/health")
if err != nil {
return err
}
return nil;
}
Now, I want to use this function as part of this struct:
type DependencyHealthFunction func() error
type Dependency struct {
Name string `json:"name"`
Required bool `json:"required"`
Healthy bool `json:"healthy"`
Error error `json:"error,omitempty"`
HealthFunction DependencyHealthFunction
}
Basically, set the value of HealthFunction to GetHealth. Now, when I do the following:
func (config *Config) GetDependencies() *health.Dependency {
vaultDependency := health.Dependency{
Name: "Vault",
Required: true,
Healthy: true,
HealthFunction: vault.Client.GetHealth,
}
temp1 := &vaultDependency
return temp1;
}
This gives me an error and it says cannot use vault.Client.GetHealth (type func(vault.Client) error) as type health.DependencyHealthFunction in field value. How can I do this?
Edit: How DependencyHealthFunction is used?
As its part of Dependency struct, it's simply used as following: d.HealthFunction() where d is a variable of type *Dependency.
This is abstract:
HealthFunction: vault.Client.GetHealth,
If we were to call HealthFunction(), what code do you expect to run? vault.Client.GetHealth is just a promise that such a function exists; it isn't a function itself. Client is just an interface.
You need to create something that conforms to Client and pass its GetHealth. For example, if you had a existing DefaultClient such as:
defaultClient := DefaultClient{}
Then you could pass its function:
HealthFunction: defaultClient.GetHealth,
Now when you later call HealthFunction() it will be the same as calling defaultClient.GetHealth().
https://play.golang.org/p/9Lw7uc0GaE
I believe the issue is related to understanding how interfaces are treated in Go.
An interface simply defines a method or set of methods that a particular type must satisfy to be considered as "implementing" the interface.
For example:
import "fmt"
type Greeter interface {
SayHello() string
}
type EnglishGreeter struct{}
// Satisfaction of SayHello method
func (eg *EnglishGreeter) SayHello() string {
return "Hello"
}
type SpanishGreeter struct{}
func (sg *SpanishGreeter) SayHello() string {
return "Ola"
}
func GreetPerson(g Greeter) {
fmt.Println(g.SayHello())
}
func main() {
eg := &EnglishGreeter{}
sg := &SpanishGreeter{}
// greet person in english
GreetPerson(eg)
// greet person in spanish
GreetPerson(sg)
}
You can add this behavior into a custom struct by simply having a Greeter field inside the struct. ie
type FrontEntrance struct {
EntranceGreeter Greeter
}
fe := &FrontEntrance { EntranceGreeter: &EnglishGreeter{} }
// then call the SayHello() method like this
fe.EntranceGreeter.SayHello()
Interfaces in golang are useful for composing common expected behavior for types based on the methods that they satisfy.
Hope this helps.

Extend struct in Go

Suppose object A has a field of type net.Dialer. I'd like to provide object A with a custom implementation of net.Dialer that augments the Dial method. Is this doable in Go? I'm trying to use embedded fields like so:
package main
import (
"net"
"fmt"
)
type dialerConsumer struct {
dialer net.Dialer
}
func (dc *dialerConsumer) use() error {
conn, e := dc.dialer.Dial("tcp", "golang.org:http")
if e != nil {
return e
}
fmt.Printf("conn: %s\n", conn)
return nil
}
type customDialer struct {
net.Dialer
}
func main() {
standardDialer := net.Dialer{}
consumer := &dialerConsumer{
dialer: standardDialer,
}
consumer.use()
/*
customDialer := customDialer{
net.Dialer{},
}
consumer = &dialerConsumer{
dialer: customDialer,
}
consumer.use()
*/
}
However, when I uncomment the commented-out code in main, I get the following compilation error:
src/test.go:38: cannot use customDialer (type customDialer) as type net.Dialer in field value
You're getting the error because customDialer and net.Dialer are two different types and cannot be used interchangeably. Embedding in Go is not the same as class inheritance in other OO langauges so it won't help you with what you trying to do.
What you can do instead in this case is to use Go interfaces which give you something like polymorphism/duck-typing, and since interfaces in Go are satified implicitly you can define a new interface that an existing type will implement by virtue of having a method with the same signature as the newly defined interface.
// already implemented by net.Dialer
type Dialer interface {
Dial(network, address string) (net.Conn, error)
}
type customDialer struct {
*net.Dialer
}
func (cd *customDialer) Dial(network, address string) (net.Conn, error) {
conn, err := cd.Dialer.Dial(network, address)
if err != nil {
return nil, err
}
fmt.Printf("conn: %s\n", conn)
return conn, nil
}
// now the dialer field can be set to *customDialer and net.Dialer as well
type dialerConsumer struct {
dialer Dialer
}
https://play.golang.org/p/i3Vpsh3wii

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