diff --git a/server/modules/monitor/mariadbmon/CMakeLists.txt b/server/modules/monitor/mariadbmon/CMakeLists.txt
index 0920a4b37..aaf8e39bb 100644
--- a/server/modules/monitor/mariadbmon/CMakeLists.txt
+++ b/server/modules/monitor/mariadbmon/CMakeLists.txt
@@ -4,3 +4,4 @@ target_link_libraries(mariadbmon maxscale-common)
 add_dependencies(mariadbmon pcre2)
 set_target_properties(mariadbmon PROPERTIES VERSION "1.4.0")
 install_module(mariadbmon core)
+add_subdirectory(test)
diff --git a/server/modules/monitor/mariadbmon/mariadbmon.hh b/server/modules/monitor/mariadbmon/mariadbmon.hh
index 717516624..9c2771f5f 100644
--- a/server/modules/monitor/mariadbmon/mariadbmon.hh
+++ b/server/modules/monitor/mariadbmon/mariadbmon.hh
@@ -42,7 +42,9 @@ private:
     MariaDBMonitor(const MariaDBMonitor&);
     MariaDBMonitor& operator = (const MariaDBMonitor&);
 public:
-    // TODO: Once done refactoring, see which of these can be moved to private.
+    // Helper class used for testing
+    class Test;
+    friend class Test;
 
     ~MariaDBMonitor();
 
diff --git a/server/modules/monitor/mariadbmon/test/CMakeLists.txt b/server/modules/monitor/mariadbmon/test/CMakeLists.txt
new file mode 100644
index 000000000..be83be2ba
--- /dev/null
+++ b/server/modules/monitor/mariadbmon/test/CMakeLists.txt
@@ -0,0 +1,3 @@
+add_executable(test_cycle_find test_cycle_find.cc)
+target_link_libraries(test_cycle_find mariadbmon maxscale-common)
+add_test(test_mariadbmon_cycle_find test_cycle_find)
\ No newline at end of file
diff --git a/server/modules/monitor/mariadbmon/test/test_cycle_find.cc b/server/modules/monitor/mariadbmon/test/test_cycle_find.cc
new file mode 100644
index 000000000..6a26d5660
--- /dev/null
+++ b/server/modules/monitor/mariadbmon/test/test_cycle_find.cc
@@ -0,0 +1,266 @@
+/*
+ * Copyright (c) 2018 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2020-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include "../mariadbmon.hh"
+#include <algorithm>
+#include <iostream>
+#include <numeric>
+#include <string>
+#include <sstream>
+#include <vector>
+#include <maxscale/alloc.h>
+#include <set>
+
+using std::string;
+using std::cout;
+
+// Maximum sizes for array types
+const int MAX_CYCLE_SIZE = 10;
+const int MAX_CYCLES = 5;
+const int MAX_EDGES = 20;
+
+class MariaDBMonitor::Test
+{
+    // These defines are required since Centos 6 doesn't support vector literal initialisers :/
+    typedef struct
+    {
+        int members[MAX_CYCLE_SIZE];
+    } CycleMembers;
+
+    typedef struct
+    {
+        CycleMembers cycles[MAX_CYCLES];
+    } CycleArray;
+
+    typedef struct
+    {
+        int slave_id;
+        int master_id;
+    } Edge;
+
+    typedef struct
+    {
+        Edge edges[MAX_EDGES];
+    } EdgeArray;
+
+public:
+    Test();
+    ~Test();
+    int run_tests();
+private:
+    MariaDBMonitor* m_monitor;
+    int m_current_test;
+
+    void init_servers(int count);
+    void clear_servers();
+    void add_replication(EdgeArray edges);
+    int check_result_cycles(CycleArray expected_cycles);
+};
+
+int main()
+{
+    MariaDBMonitor::Test tester;
+    return tester.run_tests();
+}
+
+MariaDBMonitor::Test::Test()
+    : m_monitor(new MariaDBMonitor(NULL))
+    , m_current_test(0)
+{}
+
+MariaDBMonitor::Test::~Test()
+{
+    delete m_monitor;
+}
+
+/**
+ * Runs all the tests
+ *
+ * @return Number of failures
+ */
+int MariaDBMonitor::Test::run_tests()
+{
+    std::vector<int> results;
+
+    // Test 1: 1 server, no replication
+    init_servers(1);
+    // No edges, no cycles
+    results.push_back(check_result_cycles({}));
+
+    // Test 2: 4 servers, two cycles with a connection between them
+    init_servers(4);
+    EdgeArray edges2 = {{{1,2},{2,1},{3,2},{3,4},{4,3}}};
+    add_replication(edges2);
+    CycleArray expected_cycles2 = {{{{1,2}},{{3,4}}}};
+    results.push_back(check_result_cycles(expected_cycles2));
+
+    // Test 3: 6 servers, with one cycle
+    init_servers(6);
+    EdgeArray edges3 = {{{2,1},{3,2},{4,3},{2,4},{5,1},{6,5},{6,4}}};
+    add_replication(edges3);
+    CycleArray expected_cycles3 = {{{{2,3,4}}}};
+    results.push_back(check_result_cycles(expected_cycles3));
+
+    // Test 4: 10 servers, with a big cycle composed of two smaller ones plus non-cycle servers
+    init_servers(10);
+    EdgeArray edges4 = {{{1,5},{2,1},{2,5},{3,1},{3,4},{3,10},{4,1},{5,6},{6,7},{6,4},{7,8},{8,6},{9,8}}};
+    add_replication(edges4);
+    CycleArray expected_cycles4 = {{{{1,5,6,7,8,4}}}};
+    results.push_back(check_result_cycles(expected_cycles4));
+
+    clear_servers();
+    // Return total error count
+    return std::accumulate(results.begin(), results.end(), 0);
+}
+
+/**
+ * Add dummy servers, removing any existing ones.
+ *
+ * @param count How many servers to add. Server id:s will start from 1.
+ */
+void MariaDBMonitor::Test::init_servers(int count)
+{
+    clear_servers();
+    ss_dassert(m_monitor->m_server_info.empty() && m_monitor->m_servers.empty() &&
+               m_monitor->m_servers_by_id.empty());
+
+    for (int i = 1; i < count + 1; i++)
+    {
+        SERVER* base_server = new SERVER; // Contents mostly undefined
+        std::stringstream server_name;
+        server_name << "Server" << i;
+        base_server->name = MXS_STRDUP(server_name.str().c_str());
+        MXS_MONITORED_SERVER* mon_server = new MXS_MONITORED_SERVER; // Contents mostly undefined
+        mon_server->server = base_server;
+        MariaDBServer* new_server = new MariaDBServer(mon_server);
+        new_server->m_server_id = i;
+        m_monitor->m_servers.push_back(new_server);
+        m_monitor->m_server_info[mon_server] = new_server;
+        m_monitor->m_servers_by_id[i] = new_server;
+    }
+    m_current_test++;
+}
+
+/**
+ * Clear dummy servers and free memory
+ */
+void MariaDBMonitor::Test::clear_servers()
+{
+    m_monitor->m_server_info.clear();
+    m_monitor->m_servers_by_id.clear();
+    for (auto iter = m_monitor->m_servers.begin(); iter != m_monitor->m_servers.end(); iter++)
+    {
+        MariaDBServer* server = *iter;
+        MXS_FREE(server->m_server_base->server->name);
+        delete server->m_server_base->server;
+        delete server->m_server_base;
+        delete server;
+    }
+    m_monitor->m_servers.clear();
+}
+
+/**
+ * Add replication from slave to master
+ *
+ * @param edges An array of pairs of server id:s designating replication
+ */
+void MariaDBMonitor::Test::add_replication(EdgeArray edges)
+{
+    for (auto i = 0; i < MAX_EDGES; i++)
+    {
+        auto slave_id = edges.edges[i].slave_id;
+        auto master_id = edges.edges[i].master_id;
+        if (slave_id == 0 || master_id == 0)
+        {
+            break;
+        }
+        auto iter2 = m_monitor->m_servers_by_id.find(slave_id);
+        ss_dassert(iter2 != m_monitor->m_servers_by_id.end());
+        SlaveStatus ss;
+        ss.master_server_id = master_id;
+        ss.slave_io_running = SlaveStatus::SLAVE_IO_YES;
+        (*iter2).second->m_slave_status.push_back(ss);
+    }
+    m_monitor->find_graph_cycles();
+}
+
+/**
+ * Check that the nodes have cycles as is expected. Non-cycled nodes must have cycle = 0.
+ *
+ * @param expected_cycles An array of cycles. Each cycle is an array of server id:s designating the members
+ * @return Number of failures
+ */
+int MariaDBMonitor::Test::check_result_cycles(CycleArray expected_cycles)
+{
+    std::stringstream test_name_ss;
+    test_name_ss << "Test " << m_current_test << ": ";
+    string test_name = test_name_ss.str();
+    int errors = 0;
+    // Copy the index->server map so it can be checked later
+    IdToServerMap no_cycle_servers = m_monitor->m_servers_by_id;
+    std::set<int> used_cycle_ids;
+    for (auto iter = 0; iter < MAX_CYCLES; iter++)
+    {
+        int cycle_id = 0;
+        CycleMembers cycle_member_ids = expected_cycles.cycles[iter];
+        for (auto iter2 = 0; iter2 < MAX_CYCLE_SIZE; iter2++)
+        {
+            auto search_id = cycle_member_ids.members[iter2];
+            if (search_id == 0)
+            {
+                break;
+            }
+            auto cycle_server = m_monitor->get_server(search_id);
+            if (cycle_server->m_node.cycle == 0)
+            {
+                cout << test_name << cycle_server->name() << " is not in a cycle when it should.\n";
+                errors++;
+            }
+            // If this is the first element, check what the cycle id should be for all members of the cycle.
+            else if (cycle_id == 0)
+            {
+                cycle_id = cycle_server->m_node.cycle;
+                if (used_cycle_ids.count(cycle_id) > 0)
+                {
+                    cout << test_name << cycle_server->name() << " is in unexpected cycle " <<
+                        cycle_id << ".\n";
+                    errors++;
+                }
+                else
+                {
+                    used_cycle_ids.insert(cycle_id);
+                }
+            }
+            else if (cycle_server->m_node.cycle != cycle_id)
+            {
+                cout << test_name << cycle_server->name() << " is in cycle " << cycle_server->m_node.cycle <<
+                    " when " << cycle_id << " was expected.\n";
+                errors++;
+            }
+            no_cycle_servers.erase(cycle_server->m_server_id);
+        }
+    }
+
+    // Check that servers not in expected_cycles are not in a cycle
+    for (auto iter = no_cycle_servers.begin(); iter != no_cycle_servers.end(); iter++)
+    {
+        MariaDBServer* server = (*iter).second;
+        if (server->m_node.cycle != 0)
+        {
+            cout << server->name() << " is in cycle " << server->m_node.cycle << " when none was expected.\n";
+            errors++;
+        }
+    }
+
+    return errors;
+}