distroregistry/test: make the List test generic

So we don't need to update the list when we changed the supported distros.

Signed-off-by: Ondřej Budai <ondrej@budai.cz>

internal/distroregistry/distroregistry_test.go

@@ -1,29 +1,21 @@
-package distroregistry_test
+package distroregistry
 
 import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
-
-	"github.com/osbuild/osbuild-composer/internal/distro/fedora32"
-	"github.com/osbuild/osbuild-composer/internal/distro/fedora33"
-	"github.com/osbuild/osbuild-composer/internal/distro/rhel8"
-	"github.com/osbuild/osbuild-composer/internal/distro/rhel84"
-	"github.com/osbuild/osbuild-composer/internal/distroregistry"
 )
 
 // Test that all distros are registered properly and that Registry.List() works.
 func TestRegistry_List(t *testing.T) {
-	expected := []string{
-		"centos-8",
-		"fedora-32",
-		"fedora-33",
-		"rhel-8",
-		"rhel-84",
+	// build expected distros
+	var expected []string
+	for _, distroInitializer := range supportedDistros {
+		d := distroInitializer()
+		expected = append(expected, d.Name())
 	}
 
-	distros, err := distroregistry.New(fedora32.New(), fedora33.New(), rhel8.New(), rhel84.New(), rhel84.NewCentos())
-	require.NoError(t, err)
+	distros := NewDefault()
 
 	require.ElementsMatch(t, expected, distros.List(), "unexpected list of distros")
 }