diff --git a/internal/fetch/fetchlocal_test.go b/internal/fetch/fetchlocal_test.go
new file mode 100644
index 0000000..25d7252
--- /dev/null
+++ b/internal/fetch/fetchlocal_test.go
@@ -0,0 +1,32 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fetch
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"golang.org/x/pkgsite/internal/derrors"
+	"golang.org/x/pkgsite/internal/source"
+)
+
+func TestLocalEmptyModulePath(t *testing.T) {
+	// Test local fetching when the module path is empty (corresponding to the
+	// main module of a directory). Other cases are tested in TestFetchModule.
+	ctx := context.Background()
+	got := FetchLocalModule(ctx, "", "testdata/has_go_mod", source.NewClientForTesting())
+	if got.Error != nil {
+		t.Fatal(got.Error)
+	}
+	if want := "testmod"; got.ModulePath != want {
+		t.Errorf("got %q, want %q", got.ModulePath, want)
+	}
+
+	got = FetchLocalModule(ctx, "", "testdata/no_go_mod", source.NewClientForTesting())
+	if !errors.Is(got.Error, derrors.BadModule) {
+		t.Errorf("got %v, want BadModule", got.Error)
+	}
+}
diff --git a/internal/fetch/testdata/has_go_mod/a.go b/internal/fetch/testdata/has_go_mod/a.go
new file mode 100644
index 0000000..f13289e
--- /dev/null
+++ b/internal/fetch/testdata/has_go_mod/a.go
@@ -0,0 +1,5 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
diff --git a/internal/fetch/testdata/has_go_mod/go.mod b/internal/fetch/testdata/has_go_mod/go.mod
new file mode 100644
index 0000000..c5553d5
--- /dev/null
+++ b/internal/fetch/testdata/has_go_mod/go.mod
@@ -0,0 +1 @@
+module testmod
diff --git a/internal/fetch/testdata/no_go_mod/a.go b/internal/fetch/testdata/no_go_mod/a.go
new file mode 100644
index 0000000..f13289e
--- /dev/null
+++ b/internal/fetch/testdata/no_go_mod/a.go
@@ -0,0 +1,5 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a