test: Add CChain::FindFork() tests

diff --git a/src/test/chain_tests.cpp b/src/test/chain_tests.cpp
index d2d68289..daae8f3f 100644
--- a/src/test/chain_tests.cpp
+++ b/src/test/chain_tests.cpp
@@ -7,6 +7,7 @@
 #include <chain.h>
 #include <test/util/setup_common.h>
 
+#include <array>
 #include <memory>
 
 BOOST_FIXTURE_TEST_SUITE(chain_tests, BasicTestingSetup)
@@ -85,6 +86,64 @@ BOOST_AUTO_TEST_CASE(basic_tests)
     BOOST_CHECK_EQUAL(chain_0.Genesis(), nullptr);
 }
 
+BOOST_AUTO_TEST_CASE(findfork_tests)
+{
+    // Create a forking chain
+    const auto init_branch{[](auto& blocks, CBlockIndex* parent, int start_height) {
+        for (size_t i{0}; i < blocks.size(); ++i) {
+            blocks[i].pprev = i == 0 ? parent : &blocks[i - 1];
+            blocks[i].nHeight = start_height + i;
+        }
+    }};
+
+    const auto check_same{[](const CChain& chain, const auto& blocks) {
+        for (const auto& block : blocks) {
+            BOOST_CHECK_EQUAL(chain.FindFork(&block), &block);
+        }
+    }};
+
+    const auto check_fork_point{[](const CChain& chain, const auto& blocks, const CBlockIndex& fork_point) {
+        for (const auto& block : blocks) {
+            BOOST_CHECK_EQUAL(chain.FindFork(&block), &fork_point);
+        }
+    }};
+
+    std::array<CBlockIndex, 10> blocks_common;
+    init_branch(blocks_common, nullptr, 0);
+
+    std::array<CBlockIndex, 10> blocks_long;
+    init_branch(blocks_long, &blocks_common.back(), blocks_common.size());
+
+    std::array<CBlockIndex, 5> blocks_short;
+    init_branch(blocks_short, &blocks_common.back(), blocks_common.size());
+
+    // Create a chain with the longer fork
+    CChain chain_long;
+    chain_long.SetTip(blocks_long.back());
+    BOOST_CHECK_EQUAL(chain_long.Height(), 10 + 10 - 1);
+    // Test the blocks in the common part -> result should be the same
+    check_same(chain_long, blocks_common);
+    // Test the blocks on the longer fork -> result should be the same
+    check_same(chain_long, blocks_long);
+    // Test the blocks on the other shorter fork -> result should be the fork point
+    check_fork_point(chain_long, blocks_short, blocks_common.back());
+
+    // Create a chain with the shorter fork
+    CChain chain_short;
+    chain_short.SetTip(blocks_short.back());
+    BOOST_CHECK_EQUAL(chain_short.Height(), 10 + 5 - 1);
+    // Test the blocks in the common part -> result should be the same
+    check_same(chain_short, blocks_common);
+    // Test the blocks on the shorter fork -> result should be the same
+    check_same(chain_short, blocks_short);
+    // Test the blocks on the other longer fork -> result should be the fork point
+    check_fork_point(chain_short, blocks_long, blocks_common.back());
+
+    // Invalid test case. Mixing chains is not supported
+    CBlockIndex block_on_unrelated_chain;
+    BOOST_CHECK_EQUAL(chain_long.FindFork(&block_on_unrelated_chain), nullptr);
+}
+
 BOOST_AUTO_TEST_CASE(chain_test)
 {
     FastRandomContext ctx;