Add filesystem_test.go

It has only one test function as a starting point.

Bug: n/a
Test: m (soong tests)
Change-Id: I785b096805014a40dfd600f7baaf884f4016c23c

filesystem/filesystem_test.go

@@ -0,0 +1,42 @@
+// Copyright 2021 Google Inc. 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 filesystem
+
+import (
+	"os"
+	"testing"
+
+	"android/soong/android"
+)
+
+func TestMain(m *testing.M) {
+	os.Exit(m.Run())
+}
+
+var fixture = android.GroupFixturePreparers(
+	android.PrepareForIntegrationTestWithAndroid,
+	PrepareForTestWithFilesystemBuildComponents,
+)
+
+func TestFileSystemDeps(t *testing.T) {
+	result := fixture.RunTestWithBp(t, `
+		android_filesystem {
+			name: "myfilesystem",
+		}
+	`)
+
+	// produces "myfilesystem.img"
+	result.ModuleForTests("myfilesystem", "android_common").Output("myfilesystem.img")
+}