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Sql driver mock for Golang

sqlmock is a mock library implementing sql/driver. Which has one and only purpose - to simulate any sql driver behavior in tests, without needing a real database connection. It helps to maintain correct TDD workflow.

  • this library is now complete and stable. (you may not find new changes for this reason)
  • supports concurrency and multiple connections.
  • supports go1.8 Context related feature mocking and Named sql parameters.
  • does not require any modifications to your source code.
  • the driver allows to mock any sql driver method behavior.
  • has strict by default expectation order matching.
  • has no third party dependencies.

NOTE: in v1.2.0 sqlmock.Rows has changed to struct from interface, if you were using any type references to that interface, you will need to switch it to a pointer struct type. Also, sqlmock.Rows were used to implement driver.Rows interface, which was not required or useful for mocking and was removed. Hope it will not cause issues.

Install

go get gopkg.in/DATA-DOG/go-sqlmock.v1

Documentation and Examples

Visit godoc for general examples and public api reference. See .travis.yml for supported go versions. Different use case, is to functionally test with a real database - go-txdb all database related actions are isolated within a single transaction so the database can remain in the same state.

See implementation examples:

Something you may want to test

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)
	}
}

Tests with sqlmock

package main

import (
	"fmt"
	"testing"

	"gopkg.in/DATA-DOG/go-sqlmock.v1"
)

// 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)
	}
}

Matching arguments like time.Time

There may be arguments which are of struct type and cannot be compared easily by value like time.Time. In this case sqlmock provides an Argument interface which can be used in more sophisticated matching. Here is a simple example of time argument matching:

type AnyTime struct{}

// Match satisfies sqlmock.Argument interface
func (a AnyTime) Match(v driver.Value) bool {
	_, ok := v.(time.Time)
	return ok
}

func TestAnyTimeArgument(t *testing.T) {
	t.Parallel()
	db, mock, err := New()
	if err != nil {
		t.Errorf("an error '%s' was not expected when opening a stub database connection", err)
	}
	defer db.Close()

	mock.ExpectExec("INSERT INTO users").
		WithArgs("john", AnyTime{}).
		WillReturnResult(NewResult(1, 1))

	_, err = db.Exec("INSERT INTO users(name, created_at) VALUES (?, ?)", "john", time.Now())
	if err != nil {
		t.Errorf("error '%s' was not expected, while inserting a row", err)
	}

	if err := mock.ExpectationsWereMet(); err != nil {
		t.Errorf("there were unfulfilled expections: %s", err)
	}
}

It only asserts that argument is of time.Time type.

Run tests

go test -race

Change Log

  • 2017-02-09 - implemented support for go1.8 features. Rows interface was changed to struct but contains all methods as before and should maintain backwards compatibility. ExpectedQuery.WillReturnRows may now accept multiple row sets.
  • 2016-11-02 - db.Prepare() was not validating expected prepare SQL query. It should still be validated even if Exec or Query is not executed on that prepared statement.
  • 2016-02-23 - added sqlmock.AnyArg() function to provide any kind of argument matcher.
  • 2016-02-23 - convert expected arguments to driver.Value as natural driver does, the change may affect time.Time comparison and will be stricter. See issue.
  • 2015-08-27 - v1 api change, concurrency support, all known issues fixed.
  • 2014-08-16 instead of panic during reflect type mismatch when comparing query arguments - now return error
  • 2014-08-14 added sqlmock.NewErrorResult which gives an option to return driver.Result with errors for interface methods, see issue
  • 2014-05-29 allow to match arguments in more sophisticated ways, by providing an sqlmock.Argument interface
  • 2014-04-21 introduce sqlmock.New() to open a mock database connection for tests. This method calls sql.DB.Ping to ensure that connection is open, see issue. This way on Close it will surely assert if all expectations are met, even if database was not triggered at all. The old way is still available, but it is advisable to call db.Ping manually before asserting with db.Close.
  • 2014-02-14 RowsFromCSVString is now a part of Rows interface named as FromCSVString. It has changed to allow more ways to construct rows and to easily extend this API in future. See issue 1 RowsFromCSVString is deprecated and will be removed in future

Contributions

Feel free to open a pull request. Note, if you wish to contribute an extension to public (exported methods or types) - please open an issue before, to discuss whether these changes can be accepted. All backward incompatible changes are and will be treated cautiously

License

The three clause BSD license