Add test for bad rpc server endpoint

Previously, there was a bug that made it impossible to trigger the error
"Failed to start sentinel RPC server" in sentinel::rpc::init.
With the bug fixed, the error can now be triggered.  This commit adds
a unit test that specifically triggers the error.

Signed-off-by: Michael L. Szulczewski <[email protected]>

tests/unit/sentinel_2pc/controller_test.cpp

@@ -205,3 +205,24 @@ TEST_F(sentinel_2pc_test, bad_sentinel_client_endpoint) {
                                                                 m_logger);
     ASSERT_FALSE(ctl->init());
 }
+
+TEST_F(sentinel_2pc_test, bad_rpc_server_endpoint) {
+    // The sentinel endpoint defined below (which corresponds to sentinel_id
+    // also defined below) is used by the sentinel_2pc controller to initialize
+    // an rpc server.  Replacing the valid endpoint defined in the fixture with
+    // an invalid endpoint should cause the rpc server to fail to initialize.
+    m_opts.m_sentinel_endpoints.clear();
+    constexpr auto bad_endpoint = std::make_pair("abcdefg", m_sentinel_port);
+    m_opts.m_sentinel_endpoints.resize(1);
+    m_opts.m_sentinel_endpoints.push_back(bad_endpoint);
+
+    // Initialize a new controller with the invalid endpoint for the server.
+    constexpr uint32_t sentinel_id = 0;
+    const auto ctl
+        = std::make_unique<cbdc::sentinel_2pc::controller>(sentinel_id,
+                                                           m_opts,
+                                                           m_logger);
+
+    // Check that the controller with the invalid endpoint fails to initialize.
+    ASSERT_FALSE(ctl->init());
+}