diff --git a/src/github.com/mattn/go-sqlite3/error_test.go b/src/github.com/mattn/go-sqlite3/error_test.go
new file mode 100644
index 0000000..7fccd57
--- /dev/null
+++ b/src/github.com/mattn/go-sqlite3/error_test.go
@@ -0,0 +1,242 @@
+// Copyright (C) 2014 Yasuhiro Matsumoto <mattn.jp@gmail.com>.
+//
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package sqlite3
+
+import (
+	"database/sql"
+	"io/ioutil"
+	"os"
+	"path"
+	"testing"
+)
+
+func TestSimpleError(t *testing.T) {
+	e := ErrError.Error()
+	if e != "SQL logic error or missing database" && e != "SQL logic error" {
+		t.Error("wrong error code: " + e)
+	}
+}
+
+func TestCorruptDbErrors(t *testing.T) {
+	dirName, err := ioutil.TempDir("", "sqlite3")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dirName)
+
+	dbFileName := path.Join(dirName, "test.db")
+	f, err := os.Create(dbFileName)
+	if err != nil {
+		t.Error(err)
+	}
+	f.Write([]byte{1, 2, 3, 4, 5})
+	f.Close()
+
+	db, err := sql.Open("sqlite3", dbFileName)
+	if err == nil {
+		_, err = db.Exec("drop table foo")
+	}
+
+	sqliteErr := err.(Error)
+	if sqliteErr.Code != ErrNotADB {
+		t.Error("wrong error code for corrupted DB")
+	}
+	if err.Error() == "" {
+		t.Error("wrong error string for corrupted DB")
+	}
+	db.Close()
+}
+
+func TestSqlLogicErrors(t *testing.T) {
+	dirName, err := ioutil.TempDir("", "sqlite3")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dirName)
+
+	dbFileName := path.Join(dirName, "test.db")
+	db, err := sql.Open("sqlite3", dbFileName)
+	if err != nil {
+		t.Error(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec("CREATE TABLE Foo (id INTEGER PRIMARY KEY)")
+	if err != nil {
+		t.Error(err)
+	}
+
+	const expectedErr = "table Foo already exists"
+	_, err = db.Exec("CREATE TABLE Foo (id INTEGER PRIMARY KEY)")
+	if err.Error() != expectedErr {
+		t.Errorf("Unexpected error: %s, expected %s", err.Error(), expectedErr)
+	}
+
+}
+
+func TestExtendedErrorCodes_ForeignKey(t *testing.T) {
+	dirName, err := ioutil.TempDir("", "sqlite3-err")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dirName)
+
+	dbFileName := path.Join(dirName, "test.db")
+	db, err := sql.Open("sqlite3", dbFileName)
+	if err != nil {
+		t.Error(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec("PRAGMA foreign_keys=ON;")
+	if err != nil {
+		t.Errorf("PRAGMA foreign_keys=ON: %v", err)
+	}
+
+	_, err = db.Exec(`CREATE TABLE Foo (
+		id INTEGER PRIMARY KEY AUTOINCREMENT,
+		value INTEGER NOT NULL,
+		ref INTEGER NULL REFERENCES Foo (id),
+		UNIQUE(value)
+	);`)
+	if err != nil {
+		t.Error(err)
+	}
+
+	_, err = db.Exec("INSERT INTO Foo (ref, value) VALUES (100, 100);")
+	if err == nil {
+		t.Error("No error!")
+	} else {
+		sqliteErr := err.(Error)
+		if sqliteErr.Code != ErrConstraint {
+			t.Errorf("Wrong basic error code: %d != %d",
+				sqliteErr.Code, ErrConstraint)
+		}
+		if sqliteErr.ExtendedCode != ErrConstraintForeignKey {
+			t.Errorf("Wrong extended error code: %d != %d",
+				sqliteErr.ExtendedCode, ErrConstraintForeignKey)
+		}
+	}
+
+}
+
+func TestExtendedErrorCodes_NotNull(t *testing.T) {
+	dirName, err := ioutil.TempDir("", "sqlite3-err")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dirName)
+
+	dbFileName := path.Join(dirName, "test.db")
+	db, err := sql.Open("sqlite3", dbFileName)
+	if err != nil {
+		t.Error(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec("PRAGMA foreign_keys=ON;")
+	if err != nil {
+		t.Errorf("PRAGMA foreign_keys=ON: %v", err)
+	}
+
+	_, err = db.Exec(`CREATE TABLE Foo (
+		id INTEGER PRIMARY KEY AUTOINCREMENT,
+		value INTEGER NOT NULL,
+		ref INTEGER NULL REFERENCES Foo (id),
+		UNIQUE(value)
+	);`)
+	if err != nil {
+		t.Error(err)
+	}
+
+	res, err := db.Exec("INSERT INTO Foo (value) VALUES (100);")
+	if err != nil {
+		t.Fatalf("Creating first row: %v", err)
+	}
+
+	id, err := res.LastInsertId()
+	if err != nil {
+		t.Fatalf("Retrieving last insert id: %v", err)
+	}
+
+	_, err = db.Exec("INSERT INTO Foo (ref) VALUES (?);", id)
+	if err == nil {
+		t.Error("No error!")
+	} else {
+		sqliteErr := err.(Error)
+		if sqliteErr.Code != ErrConstraint {
+			t.Errorf("Wrong basic error code: %d != %d",
+				sqliteErr.Code, ErrConstraint)
+		}
+		if sqliteErr.ExtendedCode != ErrConstraintNotNull {
+			t.Errorf("Wrong extended error code: %d != %d",
+				sqliteErr.ExtendedCode, ErrConstraintNotNull)
+		}
+	}
+
+}
+
+func TestExtendedErrorCodes_Unique(t *testing.T) {
+	dirName, err := ioutil.TempDir("", "sqlite3-err")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dirName)
+
+	dbFileName := path.Join(dirName, "test.db")
+	db, err := sql.Open("sqlite3", dbFileName)
+	if err != nil {
+		t.Error(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec("PRAGMA foreign_keys=ON;")
+	if err != nil {
+		t.Errorf("PRAGMA foreign_keys=ON: %v", err)
+	}
+
+	_, err = db.Exec(`CREATE TABLE Foo (
+		id INTEGER PRIMARY KEY AUTOINCREMENT,
+		value INTEGER NOT NULL,
+		ref INTEGER NULL REFERENCES Foo (id),
+		UNIQUE(value)
+	);`)
+	if err != nil {
+		t.Error(err)
+	}
+
+	res, err := db.Exec("INSERT INTO Foo (value) VALUES (100);")
+	if err != nil {
+		t.Fatalf("Creating first row: %v", err)
+	}
+
+	id, err := res.LastInsertId()
+	if err != nil {
+		t.Fatalf("Retrieving last insert id: %v", err)
+	}
+
+	_, err = db.Exec("INSERT INTO Foo (ref, value) VALUES (?, 100);", id)
+	if err == nil {
+		t.Error("No error!")
+	} else {
+		sqliteErr := err.(Error)
+		if sqliteErr.Code != ErrConstraint {
+			t.Errorf("Wrong basic error code: %d != %d",
+				sqliteErr.Code, ErrConstraint)
+		}
+		if sqliteErr.ExtendedCode != ErrConstraintUnique {
+			t.Errorf("Wrong extended error code: %d != %d",
+				sqliteErr.ExtendedCode, ErrConstraintUnique)
+		}
+		extended := sqliteErr.Code.Extend(3).Error()
+		expected := "constraint failed"
+		if extended != expected {
+			t.Errorf("Wrong basic error code: %q != %q",
+				extended, expected)
+		}
+	}
+
+}