validate/email_test.go

package validate

import (
	"errors"
	"fmt"
	"testing"
)

func ExampleEmail() {
	fmt.Println(Email("not an email"))
	// Output: invalid email address
}

func FuzzEmail(f *testing.F) {
	for _, seed := range []string{
		"", "alice@example.com", "not an email", "a@b",
		"Alice <alice@example.com>", "alice@example.com ",
	} {
		f.Add(seed)
	}

	f.Fuzz(func(t *testing.T, input string) {
		err := Email(input)

		// The only error Email ever returns is ErrInvalidEmail.
		if err != nil && !errors.Is(err, ErrInvalidEmail) {
			t.Fatalf("unexpected error for %q: %v", input, err)
		}

		// A verdict of "valid" must be stable on re-validation.
		if err == nil {
			if err2 := Email(input); err2 != nil {
				t.Fatalf("inconsistent verdict for %q: first nil, then %v", input, err2)
			}
		}
	})
}

func TestEmail(t *testing.T) {
	testCases := map[string]error{
		"test@example.com":                      nil,
		"firstname.lastname@some-website.co.uk": nil,
		"alice+tag@example.com":                 nil,
		"alice@localhost":                       nil, // ParseAddress does not require a dotted domain

		"not an email":              ErrInvalidEmail,
		"testexample.com":           ErrInvalidEmail,
		"Alice <alice@example.com>": ErrInvalidEmail, // display name
		"<alice@example.com>":       ErrInvalidEmail, // angle brackets
		"alice@example.com ":        ErrInvalidEmail, // trailing space
		"a@b.com, c@d.com":          ErrInvalidEmail, // address list
	}

	for input, want := range testCases {
		t.Run(input, func(t *testing.T) {
			got := Email(input)

			if !errors.Is(got, want) {
				t.Error("got", got)
				t.Error("want", want)
			}
		})
	}
}