Add simple example

Author: gmlewis

example/embed-interface/main.go

@@ -0,0 +1,40 @@
+// Copyright 2021 The go-github AUTHORS. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This embed-interface example is a copy of the "simple" example
+// and its purpose is to demonstrate how embedding an interface
+// in a struct makes it easy to mock one or more methods.
+package main
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/google/go-github/v34/github"
+)
+
+// Fetch all the public organizations' membership of a user.
+//
+func fetchOrganizations(orgService github.OrganizationsServiceInterface, username string) ([]*github.Organization, error) {
+	orgs, _, err := orgService.List(context.Background(), username, nil)
+	return orgs, err
+}
+
+func main() {
+	var username string
+	fmt.Print("Enter GitHub username: ")
+	fmt.Scanf("%s", &username)
+
+	client := github.NewClient(nil)
+	organizations, err := fetchOrganizations(client.Organizations, username)
+	if err != nil {
+		fmt.Printf("Error: %v\n", err)
+		return
+	}
+
+	for i, organization := range organizations {
+		fmt.Printf("%v. %v\n", i+1, organization.GetLogin())
+	}
+}

example/embed-interface/main_test.go

@@ -0,0 +1,45 @@
+// Copyright 2021 The go-github AUTHORS. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"context"
+	"errors"
+	"reflect"
+	"testing"
+
+	"github.com/google/go-github/v34/github"
+)
+
+type fakeOrgSvc struct {
+	github.OrganizationsServiceInterface
+
+	orgs []*github.Organization
+}
+
+func (f *fakeOrgSvc) List(ctx context.Context, org string, opts *github.ListOptions) ([]*github.Organization, *github.Response, error) {
+	if org != "octocat" {
+		return nil, nil, errors.New("unexpected org")
+	}
+
+	return f.orgs, nil, nil
+}
+
+func TestFetchOrganizations(t *testing.T) {
+	want := []*github.Organization{
+		{Name: github.String("octocat")},
+	}
+
+	orgService := &fakeOrgSvc{orgs: want}
+	got, err := fetchOrganizations(orgService, "octocat")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("got = %#v, want = %#v", got, want)
+	}
+}