Merge #16975: test: Show debug log on unit test failure

fa37e0a68bea65979f9f8f2e5258fe608acf2bdf test: Show debug log on unit test failure (MarcoFalke)

Pull request description:

  Often, it is hard to debug unit test failures without the debug log. Especially when the failure happens remotely (e.g. on a ci system).

  Fix that by printing the log on failure.

ACKs for top commit:
  jamesob:
    ACK fa37e0a68bea65979f9f8f2e5258fe608acf2bdf ([`jamesob/ackr/16975.1.MarcoFalke.test_show_debug_log_on_u`](https://github.com/jamesob/bitcoin/tree/ackr/16975.1.MarcoFalke.test_show_debug_log_on_u))

Tree-SHA512: 2ca4150c4ae3d4ad47e03b5e5e70da2baffec928ddef1fdf53a3ebc061f14aee249205387cb1b12ef6d4eb55711ef0080c0b41d9d18000b5da124ca80299793b

4 files changed, 23 insertions, 0 deletions

diff --git a/src/test/fuzz/fuzz.cpp b/src/test/fuzz/fuzz.cpp
index da4e623e9..a6ab620e2 100644
--- a/src/test/fuzz/fuzz.cpp
+++ b/src/test/fuzz/fuzz.cpp
@@ -4,10 +4,14 @@
 
 #include <test/fuzz/fuzz.h>
 
+#include <test/util/setup_common.h>
+
 #include <cstdint>
 #include <unistd.h>
 #include <vector>
 
+const std::function<void(const std::string&)> G_TEST_LOG_FUN{};
+
 static bool read_stdin(std::vector<uint8_t>& data)
 {
     uint8_t buffer[1024];
diff --git a/src/test/main.cpp b/src/test/main.cpp
index ff3f36b56..e6529949e 100644
--- a/src/test/main.cpp
+++ b/src/test/main.cpp
@@ -2,6 +2,21 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+/**
+ * See https://www.boost.org/doc/libs/1_71_0/libs/test/doc/html/boost_test/utf_reference/link_references/link_boost_test_module_macro.html
+ */
 #define BOOST_TEST_MODULE Bitcoin Core Test Suite
 
 #include <boost/test/unit_test.hpp>
+
+#include <test/util/setup_common.h>
+
+/** Redirect debug log to boost log */
+const std::function<void(const std::string&)> G_TEST_LOG_FUN = [](const std::string& s) {
+    if (s.back() == '\n') {
+        // boost will insert the new line
+        BOOST_TEST_MESSAGE(s.substr(0, s.size() - 1));
+    } else {
+        BOOST_TEST_MESSAGE(s);
+    }
+};
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index 3bdf3485f..ccb3064d5 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -71,6 +71,7 @@ BasicTestingSetup::BasicTestingSetup(const std::string& chainName)
     SelectParams(chainName);
     SeedInsecureRand();
     gArgs.ForceSetArg("-printtoconsole", "0");
+    if (G_TEST_LOG_FUN) LogInstance().PushBackCallback(G_TEST_LOG_FUN);
     InitLogging();
     LogInstance().StartLogging();
     SHA256AutoDetect();
diff --git a/src/test/util/setup_common.h b/src/test/util/setup_common.h
index 1e2e059a5..6741be848 100644
--- a/src/test/util/setup_common.h
+++ b/src/test/util/setup_common.h
@@ -18,6 +18,9 @@
 
 #include <boost/thread.hpp>
 
+/** This is connected to the logger. Can be used to redirect logs to any other log */
+extern const std::function<void(const std::string&)> G_TEST_LOG_FUN;
+
 // Enable BOOST_CHECK_EQUAL for enum class types
 template <typename T>
 std::ostream& operator<<(typename std::enable_if<std::is_enum<T>::value, std::ostream>::type& stream, const T& e)