Abandon sessions before/after running tests

See b/160281947#comment2 for the analysis.

Let's clean up staged sessions to improve test isolation.

Bug: 160281947
Test: atest StagedRollbackTest
Change-Id: I3ad6317eaee3ffb4c6351c630460dd8f1d27e644

tests/RollbackTest/NetworkStagedRollbackTest/src/com/android/tests/rollback/host/NetworkStagedRollbackTest.java

@@ -27,6 +27,7 @@ import com.android.tradefed.testtype.junit4.BaseHostJUnit4Test;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Ignore;
+import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
@@ -58,6 +59,9 @@ public class NetworkStagedRollbackTest extends BaseHostJUnit4Test {
 
     private WatchdogEventLogger mLogger = new WatchdogEventLogger();
 
+    @Rule
+    public AbandonSessionsRule mHostTestRule = new AbandonSessionsRule(this);
+
     @Before
     public void setUp() throws Exception {
         runPhase("cleanUp");

tests/RollbackTest/StagedRollbackTest/src/com/android/tests/rollback/host/StagedRollbackTest.java

@@ -34,6 +34,7 @@ import com.android.tradefed.util.CommandStatus;
 
 import org.junit.After;
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
@@ -87,6 +88,9 @@ public class StagedRollbackTest extends BaseHostJUnit4Test {
 
     private WatchdogEventLogger mLogger = new WatchdogEventLogger();
 
+    @Rule
+    public AbandonSessionsRule mHostTestRule = new AbandonSessionsRule(this);
+
     @Before
     public void setUp() throws Exception {
         deleteFiles("/system/apex/" + APK_IN_APEX_TESTAPEX_NAME + "*.apex",

tests/RollbackTest/lib/src/com/android/tests/rollback/host/AbandonSessionsRule.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2020 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.tests.rollback.host;
+
+import com.android.tradefed.device.ITestDevice;
+import com.android.tradefed.testtype.junit4.BaseHostJUnit4Test;
+
+import org.junit.rules.ExternalResource;
+
+public class AbandonSessionsRule extends ExternalResource {
+    private final BaseHostJUnit4Test mHost;
+
+    public AbandonSessionsRule(BaseHostJUnit4Test host) {
+        mHost = host;
+    }
+
+    @Override
+    protected void before() throws Throwable {
+        abandonSessions(mHost.getDevice());
+    }
+
+    @Override
+    protected void after() {
+        try {
+            abandonSessions(mHost.getDevice());
+        } catch (Exception ignore) {
+        }
+    }
+
+    /**
+     * Abandons all sessions to prevent interference in our tests.
+     */
+    private static void abandonSessions(ITestDevice device) throws Exception {
+        // No point in abandoning applied or failed sessions. We care about ready sessions only.
+        String cmdListReadySessions =
+                "pm list staged-sessions --only-sessionid --only-parent --only-ready";
+        String output = device.executeShellCommand(cmdListReadySessions);
+        if (output.trim().isEmpty()) {
+            // No sessions to abandon
+            return;
+        }
+        // Ensure we have sufficient privilege to abandon sessions from other apps
+        device.enableAdbRoot();
+        device.executeShellCommand("for i in $(" + cmdListReadySessions
+                + "); do pm install-abandon $i; done");
+        device.disableAdbRoot();
+    }
+}