Add compatibility tests.

compat.go

@@ -0,0 +1,33 @@
+package sqltest
+
+var (
+	// DriversByProduct maps a Product to the Driver implementations that it is
+	// compatible with.
+	DriversByProduct = map[Product][]Driver{}
+
+	// ProductsByDriver maps a Driver to the Product implementations that it is
+	// compatible with.
+	ProductsByDriver = map[Driver][]Product{}
+
+	// CompatiblePairs contains all compatible driver/product pairs.
+	CompatiblePairs []Pair
+)
+
+// Pair is a struct containing a driver and product that are compatible with
+// each other.
+type Pair struct {
+	Driver  Driver
+	Product Product
+}
+
+func init() {
+	for _, d := range Drivers {
+		for _, p := range Products {
+			if p.IsCompatibleWith(d) {
+				DriversByProduct[p] = append(DriversByProduct[p], d)
+				ProductsByDriver[d] = append(ProductsByDriver[d], p)
+				CompatiblePairs = append(CompatiblePairs, Pair{d, p})
+			}
+		}
+	}
+}

database.go

@@ -141,6 +141,14 @@ func (db *Database) Close() error {
 // It first checks for an environment variable containing a DSN. If that is not
 // present it askes the product to generate a default DSN.
 func dataSource(d Driver, p Product) (DataSource, error) {
+	if !p.IsCompatibleWith(d) {
+		return nil, fmt.Errorf(
+			"%s is incompatible with the '%s' driver",
+			p.Name(),
+			d.Name(),
+		)
+	}
+
 	key := strings.ToUpper(fmt.Sprintf("DOGMATIQ_TEST_DSN_%s_%s", p.Name(), d.Name()))
 	dsn := os.Getenv(key)
 
@@ -159,14 +167,6 @@ func dataSource(d Driver, p Product) (DataSource, error) {
 
 	ds, err := p.DefaultDataSource(d)
 
-	if errors.Is(err, ErrIncompatibleDriver) {
-		return nil, fmt.Errorf(
-			"%s is incompatible with the '%s' driver",
-			p.Name(),
-			d.Name(),
-		)
-	}
-
 	if err != nil {
 		return nil, fmt.Errorf(
 			"can not build a default %s DSN using the '%s' driver: %w",

driver.go

@@ -49,4 +49,12 @@ var (
 
 	// SQLite3Driver is the "sqlite3" driver (github.com/mattn/go-sqlite3).
 	SQLite3Driver Driver = sqlite3Driver{}
+
+	// Drivers is a slice containing all known products.
+	Drivers = []Driver{
+		MySQLDriver,
+		PGXDriver,
+		PostgresDriver,
+		SQLite3Driver,
+	}
 )

product.go

@@ -3,13 +3,8 @@ package sqltest
 import (
 	"context"
 	"database/sql"
-	"errors"
 )
 
-// ErrIncompatibleDriver indicates that a specific driver can not be used to
-// connect to a specific product.
-var ErrIncompatibleDriver = errors.New("the driver is not compatible with the product")
-
 // Product is a specific database product such as MySQL or MariaDB.
 //
 // The product correlates with a running service that tests are run against.
@@ -18,6 +13,9 @@ type Product interface {
 	// Name returns the human-readable name of the product.
 	Name() string
 
+	// IsCompatibleWith return true if the product is compatible with d.
+	IsCompatibleWith(d Driver) bool
+
 	// DefaultDataSource returns the default data source to use to connect to
 	// the product.
 	//
@@ -64,4 +62,12 @@ var (
 
 	// SQLite is the Product for SQLite (https://www.sqlite.org).
 	SQLite Product = sqliteProduct{}
+
+	// Products is a slice containing all known products.
+	Products = []Product{
+		MySQL,
+		MariaDB,
+		PostgreSQL,
+		SQLite,
+	}
 )

productmysql.go

@@ -25,15 +25,16 @@ func (p MySQLCompatibleProduct) Name() string {
 	return p.ProductName
 }
 
+// IsCompatibleWith return true if the product is compatible with d.
+func (p MySQLCompatibleProduct) IsCompatibleWith(d Driver) bool {
+	_, ok := d.(MySQLProtocol)
+	return ok
+}
+
 // DefaultDataSource returns the default data source to use to connect to the
 // product.
 func (p MySQLCompatibleProduct) DefaultDataSource(d Driver) (DataSource, error) {
-	proto, ok := d.(MySQLProtocol)
-	if !ok {
-		return nil, ErrIncompatibleDriver
-	}
-
-	return proto.DataSourceForMySQL(
+	return d.(MySQLProtocol).DataSourceForMySQL(
 		"root", "rootpass",
 		"127.0.0.1", p.DefaultPort,
 		"mysql",

productpostgres.go

@@ -26,15 +26,16 @@ func (p PostgresCompatibleProduct) Name() string {
 	return p.ProductName
 }
 
+// IsCompatibleWith return true if the product is compatible with d.
+func (p PostgresCompatibleProduct) IsCompatibleWith(d Driver) bool {
+	_, ok := d.(PostgresProtocol)
+	return ok
+}
+
 // DefaultDataSource returns the default data source to use to connect to the
 // product.
 func (p PostgresCompatibleProduct) DefaultDataSource(d Driver) (DataSource, error) {
-	proto, ok := d.(PostgresProtocol)
-	if !ok {
-		return nil, ErrIncompatibleDriver
-	}
-
-	return proto.DataSourceForPostgres(
+	return d.(PostgresProtocol).DataSourceForPostgres(
 		"postgres", "rootpass",
 		"127.0.0.1", p.DefaultPort,
 		"", // default database

productsqlite.go

@@ -17,13 +17,13 @@ func (sqliteProduct) Name() string {
 	return "SQLite"
 }
 
-func (sqliteProduct) DefaultDataSource(d Driver) (DataSource, error) {
-	proto, ok := d.(SQLiteProtocol)
-	if !ok {
-		return nil, ErrIncompatibleDriver
-	}
+func (sqliteProduct) IsCompatibleWith(d Driver) bool {
+	_, ok := d.(SQLiteProtocol)
+	return ok
+}
 
-	return proto.DataSourceForSQLite(
+func (sqliteProduct) DefaultDataSource(d Driver) (DataSource, error) {
+	return d.(SQLiteProtocol).DataSourceForSQLite(
 		filepath.Join(os.TempDir(), "dogmatiq.sqlite3"),
 	)
 }