feat: create mocks helper

[ncostamagna]

Fixes

create mocks helper features

used for integration test in the applications without need to send any mails

package main

import (
	"github.com/sendgrid/sendgrid-go/helpers/mock"
)

func main() {

	// Send Mail
	sendMail()

	// start mocks server
	mock.StartTestServer()

	// add mock value
	mock.Add(&mock.Mock{
		StatusCode: 400,
		Body:       `{ "errors":[{ "message":"Example error.", "field":"example field" }] }`,
	})
	sendMail() // Response with mock data

	// add mock value
	mock.Add(&mock.Mock{
		StatusCode: 200,
	})
	sendMail() // Response with mock data

	// add mock value
	mock.Add(&mock.Mock{
		Err: errors.New("Has been an mock error"),
	})

	// stop mocks server
	mock.StopTestServer()

	sendMail() // Send Mail

	// start mocks server
	mock.StartTestServer()

	sendMail() // Response with mock data

	// clear mock
	mock.Flush()
	sendMail() // Send Mail

	// stop mocks server
	mock.StopTestServer()

}

func sendMail() {
	// send Sendgrid mail
}

with a complete coverage

func TestMain(m *testing.M) {
	mock.StartTestServer()
	run := m.Run()
	mock.StopTestServer()
	os.Exit(run)
}

func TestEmailSuccess(t *testing.T) {

	mock.Add(&mock.Mock{
		StatusCode: 202,
	})

	// Test email send success
	err := myService() 
}

func TestEmailStatusError(t *testing.T) {

	mock.Add(&mock.Mock{
		StatusCode: 400,
		Body:       `{ "errors":[{ "message":"Example error.", "field":"example field" }] }`,
	})

	// Test status code error
	err := myService() 
}

func TestEmailSengridError(t *testing.T) {

	mock.Add(&mock.Mock{
		Err:        errors.New("Has been an mock error"),
	})

	// Test sendgrid error
	err := myService() 
}


func myService() error {

	// ...

	response, err := sendgrid.API(request)

	if err != nil {
		// ...
		// sendgrid error
		return err
	}
	
	if response.StatusCode > 299 {
		// ...
		// status code error
		return fmt.Errorf("code: %d, body: %s", response.StatusCode, response.Body)
	}

	// ...
	// success
	return nil

}

example in

/examples/mocks/mocks.go

Checklist

• I acknowledge that all my contributions will be made under the project's license
• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the Contribution Guidelines and my PR follows them
• I have titled the PR appropriately
• I have updated my branch with the main branch
• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary documentation about the functionality in the appropriate .md file
• I have added inline documentation to the code I modified

If you have questions, please file a support ticket, or create a GitHub Issue in this repository.

[amclay]

I love the idea, but I think it'd be more flexible to create an interface, and allow others to mock it in their own apps.

[classic-massok]

Ditto on @amclay. The idea of a built in mock is great for getting unit tests, but if this could also include interfacing out the Client I think it would provide even further flexibility for mocking. We're actually in this boat right now at our company.

[thinkingserious]

I don't like adding this dependency in non-dev environments.

[ncostamagna]

Hello @thinkingserious, how are you?
Yes, I think the same but is only place where we could intercept the request
I haven't found other place where we could intercept the request with the Mocks.

Where we could intercept the request with the mocks?

Thank you very much and greetings!

Nahuel

[thinkingserious]

I'm good, thanks for asking. I trust the same is true with you!

I think we should first create the interface per issue #421.

[ncostamagna]

Hello @thinkingserious

I created a SendGrid interface for test integration,
this example is in examples/mocks

package main

import (
	"fmt"
	"os"

	"github.com/sendgrid/sendgrid-go"
	"github.com/sendgrid/sendgrid-go/helpers/mail"
	"github.com/sendgrid/sendgrid-go/helpers/mock"
)

func main() {

	// start mocks server
	mock.StartTestServer()

	// add mock value
	mock.Add(&mock.Mock{
		StatusCode: 400,
		Body:       `{ "errors":[{ "message":"Example error.", "field":"example field" }] }`,
	})


	simpleSendMail() // Response with mock data

	// stop mocks server
	mock.StopTestServer()

}

func simpleSendMail() {
	from := mail.NewEmail("Example User", "[email protected]")
	subject := "Sending with Twilio SendGrid is Fun"
	to := mail.NewEmail("Example User", "[email protected]")
	plainTextContent := "and easy to do anywhere, even with Go"
	htmlContent := "<strong>and easy to do anywhere, even with Go</strong>"
	message := mail.NewSingleEmail(from, subject, to, plainTextContent, htmlContent)
	
	// create mock client
	client := sendgrid.NewSendClientMock(os.Getenv("SENDGRID_API_KEY"))

	response, err := client.Send(message)
	if err != nil {
		fmt.Println("Simple Sengird Error: ")
		fmt.Println(err)
		fmt.Println("________________________________")
		fmt.Println()
	} else {
		fmt.Println("Simple Sengird Response: ")
		fmt.Println(response.StatusCode)
		fmt.Println(response.Body)
		fmt.Println(response.Headers)
		fmt.Println("________________________________")
		fmt.Println()
	}
}

[thinkingserious]

Mocking should happen within the test environment.

[ncostamagna]

hello @thinkingserious
Greate, I think that would be better we use "startTest()" and "endTest()" for setting to begine and end test,
In this way, the developers doesn't depends to the name of environment variable for them project.

best regards

Nahuel

[thinkingserious]

Hello @ncostamagna,

I also agree with the comments above and the related issue #421.

What are your thoughts?

With best regards,

Elmer

[thinkingserious]

We will need an example of how to get started here.

[thinkingserious]

Please revert to the example name and email.

[ncostamagna]

Hello @thinkingserious,
the example of how to get started mocks is in line 19 for start and line 42 for end

	mock.StartTestServer() // start mock server
	
	mock.StopTestServer() // end mock server

Do I write documentation in a markdown file?

Thanks you!
Merry christmas and happy new year!

[JenniferMah]

Closing until PR feedback and failing tests are addressed.