Add test for bad coordinator endpoint

GitHub Issue mit-dci#131 identified a bug that made it impossible to trigger
the error "Failed to start coordinator client"
in sentinel_2pc::controller::init.  Since a previous commit fixed the bug,
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

@@ -169,3 +169,22 @@ TEST_F(sentinel_2pc_test, tx_validation_test) {
           });
     ASSERT_TRUE(res);
 }
+
+TEST_F(sentinel_2pc_test, bad_coordinator_endpoint) {
+    // Replace the valid coordinator endpoint defined in the fixture
+    // with an invalid endpoint.
+    m_opts.m_coordinator_endpoints.clear();
+    const auto bad_coordinator_ep
+        = std::make_pair("abcdefg", m_coordinator_port);
+    m_opts.m_coordinator_endpoints.resize(1);
+    m_opts.m_coordinator_endpoints[0].push_back(bad_coordinator_ep);
+
+    // Initialize a new controller with the invalid controller endpoint.
+    auto ctl = std::make_unique<cbdc::sentinel_2pc::controller>(0,
+                                                                m_opts,
+                                                                m_logger);
+
+    // Check that the controller with the invalid coordinator enpoint
+    // fails to initialize correctly.
+    ASSERT_FALSE(ctl->init());
+}