Move unittest constants to header

Allows unittests to easly access these constants w/o having to declare
extern const char* bla;

Test: th
Change-Id: I0bf6637430104c3d621277a725721ca61c6ac544
diff --git a/common/test_utils.h b/common/test_utils.h
index bb5a678..631ded4 100644
--- a/common/test_utils.h
+++ b/common/test_utils.h
@@ -33,6 +33,7 @@
 #include <gtest/gtest.h>
 
 #include "update_engine/common/action.h"
+#include "update_engine/common/testing_constants.h"
 #include "update_engine/common/utils.h"
 #include "update_engine/update_metadata.pb.h"
 
diff --git a/common/testing_constants.h b/common/testing_constants.h
new file mode 100644
index 0000000..1367ce6
--- /dev/null
+++ b/common/testing_constants.h
@@ -0,0 +1,39 @@
+//
+// Copyright (C) 2021 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.
+//
+
+#ifndef UPDATE_ENGINE_COMMON_TESTING_CONSTANTS_H_
+#define UPDATE_ENGINE_COMMON_TESTING_CONSTANTS_H_
+
+[[maybe_unused]]
+static constexpr auto&& kUnittestPrivateKeyPath = "unittest_key.pem";
+[[maybe_unused]]
+static constexpr auto&& kUnittestPublicKeyPath = "unittest_key.pub.pem";
+[[maybe_unused]]
+static constexpr auto&& kUnittestPrivateKey2Path = "unittest_key2.pem";
+[[maybe_unused]]
+static constexpr auto&& kUnittestPublicKey2Path = "unittest_key2.pub.pem";
+[[maybe_unused]]
+static constexpr auto&& kUnittestPrivateKeyRSA4096Path =
+    "unittest_key_RSA4096.pem";
+[[maybe_unused]]
+static constexpr auto&& kUnittestPublicKeyRSA4096Path =
+    "unittest_key_RSA4096.pub.pem";
+[[maybe_unused]]
+static constexpr auto&& kUnittestPrivateKeyECPath = "unittest_key_EC.pem";
+[[maybe_unused]]
+static constexpr auto&& kUnittestPublicKeyECPath = "unittest_key_EC.pub.pem";
+
+#endif  // UPDATE_ENGINE_COMMON_TESTING_CONSTANTS_H_