test: Add regression test for getmininginfo difficulty algorithm (issue #346)

Add test_getmininginfo_difficulty_algorithm() to verify that the
'difficulty' field in getmininginfo matches the difficulty for the
current mining algorithm (pow_algo), not a hardcoded algorithm.

This prevents regression of issue #346 where the difficulty field
always returned Groestl's difficulty regardless of the configured
mining algorithm.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: gto90

test/functional/feature_digibyte_multialgo_mining.py

@@ -370,12 +370,57 @@ def test_generateblock_rpc(self):
         # Should use default algorithm (scrypt)
         assert_equal(block['pow_algo'], 'scrypt')
 
+    def test_getmininginfo_difficulty_algorithm(self):
+        """Test that getmininginfo difficulty matches current mining algorithm.
+
+        Regression test for issue #346: The 'difficulty' field was always
+        returning Groestl's difficulty (algo=2) instead of the current
+        mining algorithm's difficulty due to a missing parameter in the
+        GetDifficulty() call.
+        """
+        self.log.info("Testing getmininginfo difficulty matches current algorithm (issue #346)...")
+
+        node = self.nodes[0]
+
+        # Get mining info
+        info = node.getmininginfo()
+
+        # Get the current mining algorithm name
+        current_algo = info['pow_algo']
+
+        # The 'difficulty' field should match the difficulty for the current algorithm
+        # Before the fix, this would return groestl's difficulty regardless of pow_algo
+        expected_difficulty = info['difficulties'][current_algo]
+        actual_difficulty = info['difficulty']
+
+        self.log.info(f"Current algorithm: {current_algo}")
+        self.log.info(f"Expected difficulty (from difficulties.{current_algo}): {expected_difficulty}")
+        self.log.info(f"Actual difficulty field: {actual_difficulty}")
+
+        assert_equal(actual_difficulty, expected_difficulty,
+            f"getmininginfo 'difficulty' should match 'difficulties.{current_algo}'. "
+            f"Got {actual_difficulty}, expected {expected_difficulty}. "
+            f"This may indicate issue #346 regression.")
+
+        # Additional sanity check: if we have multiple algorithms with different
+        # difficulties, verify we're not just getting lucky
+        difficulties = info['difficulties']
+        if len(set(difficulties.values())) > 1:
+            # We have different difficulties for different algorithms
+            # Verify we're returning the right one, not just any one
+            for algo_name, algo_diff in difficulties.items():
+                if algo_name != current_algo and algo_diff != expected_difficulty:
+                    self.log.info(f"Verified: difficulty differs from {algo_name} ({algo_diff})")
+                    break
+
+        self.log.info("getmininginfo difficulty algorithm test passed!")
+
     def test_mining_info_comprehensive(self):
         """Comprehensive test of getmininginfo output."""
         self.log.info("Testing comprehensive getmininginfo output...")
-        
+
         node = self.nodes[0]
-        
+
         # Get mining info
         info = node.getmininginfo()
 
@@ -437,11 +482,14 @@ def run_test(self):
 
         # Test 7: Comprehensive mining info
         self.test_mining_info_comprehensive()
-        
-        # Test 8: Difficulty adjustment
+
+        # Test 8: getmininginfo difficulty matches algorithm (issue #346 regression test)
+        self.test_getmininginfo_difficulty_algorithm()
+
+        # Test 9: Difficulty adjustment
         self.test_difficulty_adjustment()
-        
-        # Test 9: Odocrypt activation (if height permits)
+
+        # Test 10: Odocrypt activation (if height permits)
         if ODOCRYPT_HEIGHT < 1000:  # Only test if reasonable for regtest
             self.test_odocrypt_activation()