Create integration test for fastboot CLI

We rely on parsing the `fastboot devices` output in device labs, and a
format change previously broke us. This test will ensure that the output
is exactly what we expect.

Test: atest --host fastboot_integration_test

Change-Id: I7606e7b3e4a1edfe487ff14bb06cbd3c0a3aa777

fastboot/Android.bp

@@ -446,3 +446,14 @@ cc_library_headers {
     host_supported: true,
     export_include_dirs: ["."],
 }
+
+python_test_host {
+    name: "fastboot_integration_test",
+    main: "test_fastboot.py",
+    srcs: ["test_fastboot.py"],
+    data: [":fastboot"],
+    test_config: "fastboot_integration_test.xml",
+    test_options: {
+        unit_test: false,
+    },
+}

fastboot/fastboot_integration_test.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2023 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.
+-->
+<configuration description="Config to run fastboot integration tests">
+    <option name="test-suite-tag" value="fastboot_unittests" />
+    <test class="com.android.tradefed.testtype.python.PythonBinaryHostTest" >
+        <option name="par-file-name" value="fastboot_integration_test" />
+        <option name="test-timeout" value="1m" />
+    </test>
+</configuration>

fastboot/test_fastboot.py

@@ -0,0 +1,53 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2023 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.
+#
+"""Tests for the fastboot command line utility.
+"""
+
+import re
+import subprocess
+import unittest
+
+
+class DevicesTest(unittest.TestCase):
+    """Tests for `fastboot devices`."""
+
+
+    def test_devices(self):
+        """Ensure that the format of `fastboot devices` does not change.
+
+        `fastboot devices` should alternate between a line containing the
+        device's serial number and fastboot state and an empty line
+        """
+        output = subprocess.check_output(["fastboot", "devices"])
+
+        previous_line_was_empty = True
+        for line in output.decode().splitlines():
+            if previous_line_was_empty:
+                if not re.match(r"[a-zA-Z\d]+\s+(bootloader|fastbootd)", line):
+                    self.fail("%s does not match the expected format <serial no>\\s+(bootloader|fastbootd)" % line)
+                previous_line_was_empty = False
+            else:
+                if line:
+                    self.fail("Expected an empty line. Received '%s'" % line)
+                previous_line_was_empty = True
+
+        if len(output) == 0:
+            self.fail("Output is empty. Are any devices connected?")
+
+
+if __name__ == '__main__':
+    unittest.main()