tests: Add test suite shared identity management fixture

This is one of the two commits for issue #1683.
This one provides an identity management fixture which will be used to replace the existing
global IdentityFixture in the second commit.

Change-Id: I2eecaa2ee73661db328760ac957474791ff59112
Refs: #1683
diff --git a/tests/unit-tests/transport/test-unix-transport.cpp b/tests/unit-tests/transport/test-unix-transport.cpp
index 6c20302..7812664 100644
--- a/tests/unit-tests/transport/test-unix-transport.cpp
+++ b/tests/unit-tests/transport/test-unix-transport.cpp
@@ -31,12 +31,12 @@
 public:
   UnixTransportFixture()
   {
-    m_HOME = std::getenv("HOME");
+    m_HOME = std::getenv("TEST_HOME");
   }
 
   ~UnixTransportFixture()
   {
-    setenv("HOME", m_HOME.c_str(), 1);
+    setenv("TEST_HOME", m_HOME.c_str(), 1);
     // std::cerr << "restoring home = " << m_HOME << std::endl;
   }
 
@@ -48,7 +48,7 @@
 
 BOOST_AUTO_TEST_CASE(TestGetDefaultSocketNameOk)
 {
-  setenv("HOME", "tests/unit-tests/transport/test-homes/ok", 1);
+  setenv("TEST_HOME", "tests/unit-tests/transport/test-homes/ok", 1);
 
   ConfigFile config;
   BOOST_REQUIRE_EQUAL(UnixTransport::getDefaultSocketName(config), "/tmp/test/nfd.sock");
@@ -56,21 +56,24 @@
 
 BOOST_AUTO_TEST_CASE(TestGetDefaultSocketNameMissingSocketMissingProtocol)
 {
-  setenv("HOME", "tests/unit-tests/transport/test-homes/missing-unix-socket-missing-protocol", 1);
+  setenv("TEST_HOME",
+         "tests/unit-tests/transport/test-homes/missing-unix-socket-missing-protocol", 1);
   ConfigFile config;
   BOOST_REQUIRE_EQUAL(UnixTransport::getDefaultSocketName(config), "/var/run/nfd.sock");
 }
 
 BOOST_AUTO_TEST_CASE(TestGetDefaultSocketNameMissingSocketNdndProtocol)
 {
-  setenv("HOME", "tests/unit-tests/transport/test-homes/missing-unix-socket-with-ndnd-protocol", 1);
+  setenv("TEST_HOME",
+         "tests/unit-tests/transport/test-homes/missing-unix-socket-with-ndnd-protocol", 1);
   ConfigFile config;
   BOOST_REQUIRE_EQUAL(UnixTransport::getDefaultSocketName(config), "/tmp/.ndnd.sock");
 }
 
 BOOST_AUTO_TEST_CASE(TestGetDefaultSocketNameMissingSocketWithProtocol)
 {
-  setenv("HOME", "tests/unit-tests/transport/test-homes/missing-unix-socket-with-protocol", 1);
+  setenv("TEST_HOME",
+         "tests/unit-tests/transport/test-homes/missing-unix-socket-with-protocol", 1);
   ConfigFile config;
   BOOST_REQUIRE_EQUAL(UnixTransport::getDefaultSocketName(config), "/var/run/nfd.sock");
 }