test: parse the command line arguments in unit tests

Retrieve the command line arguments from boost and pass them to
`BasicTestingSetup` so that we gain extra flexibility of passing any
config options on the test command line, e.g.:

```
test_bitcoin -- -printtoconsole=1 -checkaddrman=5
```

5 files changed, 51 insertions, 12 deletions

diff --git a/src/test/README.md b/src/test/README.md
index d03411c3ed..90d0e7102d 100644
--- a/src/test/README.md
+++ b/src/test/README.md
@@ -33,19 +33,31 @@ the `src/qt/test/test_main.cpp` file.
 
 ### Running individual tests
 
-`test_bitcoin` has some built-in command-line arguments; for
-example, to run just the `getarg_tests` verbosely:
+`test_bitcoin` accepts the command line arguments from the boost framework.
+For example, to run just the `getarg_tests` suite of tests:
 
-    test_bitcoin --log_level=all --run_test=getarg_tests -- DEBUG_LOG_OUT
+```bash
+test_bitcoin --log_level=all --run_test=getarg_tests
+```
 
 `log_level` controls the verbosity of the test framework, which logs when a
-test case is entered, for example. The `DEBUG_LOG_OUT` after the two dashes
-redirects the debug log, which would normally go to a file in the test datadir
+test case is entered, for example. `test_bitcoin` also accepts the command
+line arguments accepted by `bitcoind`. Use `--` to separate both types of
+arguments:
+
+```bash
+test_bitcoin --log_level=all --run_test=getarg_tests -- -printtoconsole=1
+```
+
+The `-printtoconsole=1` after the two dashes redirects the debug log, which
+would normally go to a file in the test datadir
 (`BasicTestingSetup::m_path_root`), to the standard terminal output.
 
 ... or to run just the doubledash test:
 
-    test_bitcoin --run_test=getarg_tests/doubledash
+```bash
+test_bitcoin --run_test=getarg_tests/doubledash
+```
 
 Run `test_bitcoin --help` for the full list.
 
@@ -68,7 +80,7 @@ on failure. For running individual tests verbosely, refer to the section
 To write to logs from unit tests you need to use specific message methods
 provided by Boost. The simplest is `BOOST_TEST_MESSAGE`.
 
-For debugging you can launch the `test_bitcoin` executable with `gdb`or `lldb` and
+For debugging you can launch the `test_bitcoin` executable with `gdb` or `lldb` and
 start debugging, just like you would with any other program:
 
 ```bash
@@ -95,7 +107,7 @@ Running the tests and hitting a segmentation fault should now produce a file cal
 `/proc/sys/kernel/core_pattern`).
 
 You can then explore the core dump using
-``` bash
+```bash
 gdb src/test/test_bitcoin core
 
 (gbd) bt  # produce a backtrace for where a segfault occurred
diff --git a/src/test/fuzz/fuzz.cpp b/src/test/fuzz/fuzz.cpp
index a33297e0ed..1c994a53cf 100644
--- a/src/test/fuzz/fuzz.cpp
+++ b/src/test/fuzz/fuzz.cpp
@@ -12,6 +12,7 @@
 
 #include <cstdint>
 #include <exception>
+#include <functional>
 #include <memory>
 #include <string>
 #include <unistd.h>
@@ -19,6 +20,8 @@
 
 const std::function<void(const std::string&)> G_TEST_LOG_FUN{};
 
+const std::function<std::vector<const char*>()> G_TEST_COMMAND_LINE_ARGUMENTS{};
+
 std::map<std::string_view, std::tuple<TypeTestOneInput, TypeInitialize, TypeHidden>>& FuzzTargets()
 {
     static std::map<std::string_view, std::tuple<TypeTestOneInput, TypeInitialize, TypeHidden>> g_fuzz_targets;
diff --git a/src/test/main.cpp b/src/test/main.cpp
index 5885564074..1ad8fcce3a 100644
--- a/src/test/main.cpp
+++ b/src/test/main.cpp
@@ -11,6 +11,7 @@
 
 #include <test/util/setup_common.h>
 
+#include <functional>
 #include <iostream>
 
 /** Redirect debug log to unit_test.log files */
@@ -24,3 +25,17 @@ const std::function<void(const std::string&)> G_TEST_LOG_FUN = [](const std::str
     if (!should_log) return;
     std::cout << s;
 };
+
+/**
+ * Retrieve the command line arguments from boost.
+ * Allows usage like:
+ * `test_bitcoin --run_test="net_tests/cnode_listen_port" -- -checkaddrman=1 -printtoconsole=1`
+ * which would return `["-checkaddrman=1", "-printtoconsole=1"]`.
+ */
+const std::function<std::vector<const char*>()> G_TEST_COMMAND_LINE_ARGUMENTS = []() {
+    std::vector<const char*> args;
+    for (int i = 1; i < boost::unit_test::framework::master_test_suite().argc; ++i) {
+        args.push_back(boost::unit_test::framework::master_test_suite().argv[i]);
+    }
+    return args;
+};
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index 87546f45f2..b41c2aa12f 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -42,6 +42,7 @@
 #include <walletinitinterface.h>
 
 #include <functional>
+#include <stdexcept>
 
 using node::BlockAssembler;
 using node::CalculateCacheSizes;
@@ -88,7 +89,7 @@ BasicTestingSetup::BasicTestingSetup(const std::string& chainName, const std::ve
       m_args{}
 {
     m_node.args = &gArgs;
-    const std::vector<const char*> arguments = Cat(
+    std::vector<const char*> arguments = Cat(
         {
             "dummy",
             "-printtoconsole=0",
@@ -100,6 +101,9 @@ BasicTestingSetup::BasicTestingSetup(const std::string& chainName, const std::ve
             "-debugexclude=leveldb",
         },
         extra_args);
+    if (G_TEST_COMMAND_LINE_ARGUMENTS) {
+        arguments = Cat(arguments, G_TEST_COMMAND_LINE_ARGUMENTS());
+    }
     util::ThreadRename("test");
     fs::create_directories(m_path_root);
     m_args.ForceSetArg("-datadir", fs::PathToString(m_path_root));
@@ -108,9 +112,10 @@ BasicTestingSetup::BasicTestingSetup(const std::string& chainName, const std::ve
     {
         SetupServerArgs(*m_node.args);
         std::string error;
-        const bool success{m_node.args->ParseParameters(arguments.size(), arguments.data(), error)};
-        assert(success);
-        assert(error.empty());
+        if (!m_node.args->ParseParameters(arguments.size(), arguments.data(), error)) {
+            m_node.args->ClearArgs();
+            throw std::runtime_error{error};
+        }
     }
     SelectParams(chainName);
     SeedInsecureRand();
diff --git a/src/test/util/setup_common.h b/src/test/util/setup_common.h
index 58ffd77995..a1b7525cf4 100644
--- a/src/test/util/setup_common.h
+++ b/src/test/util/setup_common.h
@@ -19,12 +19,16 @@
 #include <util/string.h>
 #include <util/vector.h>
 
+#include <functional>
 #include <type_traits>
 #include <vector>
 
 /** 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;
 
+/** Retrieve the command line arguments. */
+extern const std::function<std::vector<const char*>()> G_TEST_COMMAND_LINE_ARGUMENTS;
+
 // Enable BOOST_CHECK_EQUAL for enum class types
 namespace std {
 template <typename T>