Tweaks to enhance testability

1) Add two entry points to SystemInterface:
   - getFilesDir(): returns a directory where permanent data can be stored (by default Context.getFilesDir())
                    This allows components under test to store data without affecting the real version of the files
   - getCurrentUptime(): returns the length of time that the system has been running (by default via SystemClock)
                         This is useful to enable testing of time-sensitive components

2) Add a TemporaryDirectory helper with the same semantics as TemporaryFile.
   Move both TemporaryFile and TemporaryDirectory to their own package in order to share between carservice_test and carservice_unit_test

Bug: 32512551
Test: runtest -x packages/services/Car/tests/carservice_unit_test
      runtest -x packages/services/Car/tests/carservice_unit_test/src/com/android/car/CarPowerManagementServiceTest.java
      runtest -x packages/services/Car/tests/carservice_test/src/com/android/car/CarStorageMonitoringTest.java

Change-Id: I31480cbd6b66df83804cc331d8c25a1403f10fe7

3 files changed, 168 insertions, 0 deletions

diff --git a/tests/common_utils/Android.mk b/tests/common_utils/Android.mk
new file mode 100644
index 0000000000..19302c6033
--- /dev/null
+++ b/tests/common_utils/Android.mk
@@ -0,0 +1,26 @@
+# Copyright (C) 2017 The Android Open Source Project
+#
+# 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.
+#
+
+LOCAL_PATH:= $(call my-dir)
+
+include $(CLEAR_VARS)
+
+LOCAL_MODULE := com.android.car.test.utils
+
+LOCAL_MODULE_TAGS := optional
+
+LOCAL_SRC_FILES := $(call all-java-files-under, src)
+
+include $(BUILD_STATIC_JAVA_LIBRARY)
diff --git a/tests/common_utils/src/com/android/car/test/utils/TemporaryDirectory.java b/tests/common_utils/src/com/android/car/test/utils/TemporaryDirectory.java
new file mode 100644
index 0000000000..fa5727d903
--- /dev/null
+++ b/tests/common_utils/src/com/android/car/test/utils/TemporaryDirectory.java
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * 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 com.android.car.test.utils;
+
+import android.annotation.Nullable;
+import android.os.SystemClock;
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.FileVisitResult;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
+
+/**
+ * A utility class that creates a temporary directory.
+ * The directory, and any files contained within, are automatically deleted when calling close().
+ *
+ * Example usage:
+ *
+ * try (TemporaryDirectory tf = new TemporaryDirectory("myTest")) {
+ *     ...
+ * } // directory gets deleted here
+ */
+public class TemporaryDirectory implements AutoCloseable {
+    private Path mDirectory;
+
+    private static final class DeletingVisitor extends SimpleFileVisitor<Path> {
+        FileVisitResult consume(Path path) throws IOException {
+            Files.delete(path);
+            return FileVisitResult.CONTINUE;
+        }
+
+        @Override
+        public FileVisitResult visitFile(Path path, BasicFileAttributes basicFileAttributes)
+                throws IOException {
+            return consume(path);
+        }
+
+        @Override
+        public FileVisitResult postVisitDirectory(Path path, IOException e)
+                throws IOException {
+            return consume(path);
+        }
+    }
+
+    private static final SimpleFileVisitor<Path> DELETE = new DeletingVisitor();
+
+    public TemporaryDirectory(@Nullable String prefix) throws IOException {
+        if (prefix == null) {
+            prefix = TemporaryDirectory.class.getSimpleName();
+        }
+        prefix += String.valueOf(SystemClock.elapsedRealtimeNanos());
+
+        mDirectory = Files.createTempDirectory(prefix);
+    }
+
+    @Override
+    public void close() throws Exception {
+        Files.walkFileTree(mDirectory, DELETE);
+    }
+
+    public File getDirectory() {
+        return mDirectory.toFile();
+    }
+}
diff --git a/tests/common_utils/src/com/android/car/test/utils/TemporaryFile.java b/tests/common_utils/src/com/android/car/test/utils/TemporaryFile.java
new file mode 100644
index 0000000000..a26c1ab98c
--- /dev/null
+++ b/tests/common_utils/src/com/android/car/test/utils/TemporaryFile.java
@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * 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 com.android.car.test.utils;
+
+import android.annotation.Nullable;
+import android.os.SystemClock;
+
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+
+/**
+ * A utility class that creates a temporary file.
+ * The file is automatically deleted when calling close().
+ *
+ * Example usage:
+ *
+ * try (TemporaryFile tf = new TemporaryFile("myTest")) {
+ *     ...
+ * } // file gets deleted here
+ */
+public final class TemporaryFile implements AutoCloseable {
+    private File mFile;
+
+    public TemporaryFile(@Nullable String prefix) throws IOException {
+        if (prefix == null) {
+            prefix = TemporaryFile.class.getSimpleName();
+        }
+        mFile = File.createTempFile(prefix, String.valueOf(SystemClock.elapsedRealtimeNanos()));
+    }
+
+    @Override
+    public void close() throws Exception {
+        Files.delete(mFile.toPath());
+    }
+
+    public void write(String s) throws IOException {
+        BufferedWriter writer = new BufferedWriter(new FileWriter(mFile));
+        writer.write(s);
+        writer.close();
+    }
+
+    public File getFile() {
+        return mFile;
+    }
+}