[878] Fix in ifacemgr_unittest: separate instances are now used

Tests used single instance of IfaceMgr (it is singleton after all).
Therefore first fake interface data was reused in later tests,
causing them to fail.

src/bin/dhcp6/tests/iface_mgr_unittest.cc

@@ -112,7 +112,7 @@ TEST_F(IfaceMgrTest, detectIfaces) {
     // test detects that interfaces can be detected
     // there is no code for that now, but interfaces are
     // read from file
-    fstream fakeifaces("interfaces.txt", ios::out);
+    fstream fakeifaces("interfaces.txt", ios::out|ios::trunc);
     fakeifaces << "eth0 fe80::1234";
     fakeifaces.close();
 
@@ -120,11 +120,11 @@ TEST_F(IfaceMgrTest, detectIfaces) {
     // interfaces. Nevertheless, this fake interface should
     // be on list, but if_nametoindex() will fail.
 
-    IfaceMgr & ifacemgr = IfaceMgr::instance();
+    NakedIfaceMgr * ifacemgr = new NakedIfaceMgr();
 
-    ASSERT_TRUE( ifacemgr.getIface("eth0") != NULL );
+    ASSERT_TRUE( ifacemgr->getIface("eth0") != NULL );
 
-    IfaceMgr::Iface * eth0 = ifacemgr.getIface("eth0");
+    IfaceMgr::Iface * eth0 = ifacemgr->getIface("eth0");
 
     // there should be one address
     EXPECT_EQ(1, eth0->addrs_.size());
@@ -133,6 +133,8 @@ TEST_F(IfaceMgrTest, detectIfaces) {
     ASSERT_TRUE( addr != NULL );
 
     EXPECT_STREQ( "fe80::1234", addr->toText().c_str() );
+
+    delete ifacemgr;
 }
 
 TEST_F(IfaceMgrTest, sockets) {
@@ -163,7 +165,7 @@ TEST_F(IfaceMgrTest, sendReceive) {
     // testing socket operation in a portable way is tricky
     // without interface detection implemented
 
-    fstream fakeifaces("interfaces.txt", ios::out);
+    fstream fakeifaces("interfaces.txt", ios::out|ios::trunc);
     fakeifaces << "lo ::1";
     fakeifaces.close();