update readme and add example

* dcca987 add an old example and a basic one

examples/basic/basic.go

@@ -0,0 +1,40 @@
+package main
+
+import "database/sql"
+
+func recordStats(db *sql.DB, userID, productID int64) (err error) {
+	tx, err := db.Begin()
+	if err != nil {
+		return
+	}
+
+	defer func() {
+		switch err {
+		case nil:
+			err = tx.Commit()
+		default:
+			tx.Rollback()
+		}
+	}()
+
+	if _, err = tx.Exec("UPDATE products SET views = views + 1"); err != nil {
+		return
+	}
+	if _, err = tx.Exec("INSERT INTO product_viewers (user_id, product_id) VALUES (?, ?)", userID, productID); err != nil {
+		return
+	}
+	return
+}
+
+func main() {
+	// @NOTE: the real connection is not required for tests
+	db, err := sql.Open("mysql", "root@/blog")
+	if err != nil {
+		panic(err)
+	}
+	defer db.Close()
+
+	if err = recordStats(db, 1 /*some user id*/, 5 /*some product id*/); err != nil {
+		panic(err)
+	}
+}

examples/basic/basic_test.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+)
+
+// a successful case
+func TestShouldUpdateStats(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("an error '%s' was not expected when opening a stub database connection", err)
+	}
+	defer db.Close()
+
+	mock.ExpectBegin()
+	mock.ExpectExec("UPDATE products").WillReturnResult(sqlmock.NewResult(1, 1))
+	mock.ExpectExec("INSERT INTO product_viewers").WithArgs(2, 3).WillReturnResult(sqlmock.NewResult(1, 1))
+	mock.ExpectCommit()
+
+	// now we execute our method
+	if err = recordStats(db, 2, 3); err != nil {
+		t.Errorf("error was not expected while updating stats: %s", err)
+	}
+
+	// we make sure that all expectations were met
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("there were unfulfilled expections: %s", err)
+	}
+}
+
+// a failing test case
+func TestShouldRollbackStatUpdatesOnFailure(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("an error '%s' was not expected when opening a stub database connection", err)
+	}
+	defer db.Close()
+
+	mock.ExpectBegin()
+	mock.ExpectExec("UPDATE products").WillReturnResult(sqlmock.NewResult(1, 1))
+	mock.ExpectExec("INSERT INTO product_viewers").
+		WithArgs(2, 3).
+		WillReturnError(fmt.Errorf("some error"))
+	mock.ExpectRollback()
+
+	// now we execute our method
+	if err = recordStats(db, 2, 3); err == nil {
+		t.Errorf("was expecting an error, but there was none")
+	}
+
+	// we make sure that all expectations were met
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("there were unfulfilled expections: %s", err)
+	}
+}