diff --git a/htesting/testdata_builder.go b/htesting/testdata_builder.go
new file mode 100644
index 00000000000..437c2ad2f62
--- /dev/null
+++ b/htesting/testdata_builder.go
@@ -0,0 +1,39 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package htesting
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/spf13/afero"
+)
+
+type testdataBuilder struct {
+	t          testing.TB
+	fs         afero.Fs
+	workingDir string
+}
+
+func NewTestdataBuilder(fs afero.Fs, workingDir string, t testing.TB) *testdataBuilder {
+	workingDir = filepath.Clean(workingDir)
+	return &testdataBuilder{fs: fs, workingDir: workingDir, t: t}
+}
+
+func (b *testdataBuilder) Add(filename, content string) *testdataBuilder {
+	if err := afero.WriteFile(b.fs, filepath.Join(b.workingDir, filename), []byte(content), 0666); err != nil {
+		b.t.Fatalf("failed to add %q: %s", filename, err)
+	}
+	return b
+}
diff --git a/hugolib/config.go b/hugolib/config.go
index 77ebb42ae6f..aa7a78e0ce7 100644
--- a/hugolib/config.go
+++ b/hugolib/config.go
@@ -74,6 +74,9 @@ type ConfigSourceDescriptor struct {
 
 	// The project's working dir. Is used to look for additional theme config.
 	WorkingDir string
+
+	// The (optional) directory for additional configuration files.
+	AbsConfigDir string
 }
 
 func (d ConfigSourceDescriptor) configFilenames() []string {
diff --git a/hugolib/configdir_test.go b/hugolib/configdir_test.go
new file mode 100644
index 00000000000..03c21de3f29
--- /dev/null
+++ b/hugolib/configdir_test.go
@@ -0,0 +1,46 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hugolib
+
+import (
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/require"
+)
+
+func TestLoadConfigDir(t *testing.T) {
+	t.Parallel()
+
+	assert := require.New(t)
+
+	// Add a random config variable for testing.
+	// side = page in Norwegian.
+	configContent := `
+paginatePath = "side"
+`
+
+	mm := afero.NewMemMapFs()
+
+	writeToFs(t, mm, "hugo.toml", configContent)
+
+	cfg, _, err := LoadConfig(ConfigSourceDescriptor{Fs: mm, Filename: "hugo.toml"})
+	require.NoError(t, err)
+
+	assert.Equal("side", cfg.GetString("paginatePath"))
+	// default
+	assert.Equal("layouts", cfg.GetString("layoutDir"))
+	// no themes
+	assert.False(cfg.IsSet("allThemes"))
+}