dgb: wire src/impl/dgb/test share fixtures (oracle consensus-identity guard)

Enable add_subdirectory(test) and add dgb_share_test, mirroring the
ltc/btc test pattern. The test links the dgb OBJECT lib (pool/share TU)
into a gtest executable, build-verifying the Phase-B pool/share stack,
and asserts the DGB-oracle-conformed (frstrtr/p2pool-dgb-scrypt)
consensus + sharechain-identity params adjudicated at prescan-DGB:

  - IDENTIFIER 4b62545b1a631afe / PREFIX 1c0553f23ebfcffe (isolation
    primitives — must stay byte-exact per coin)
  - SEGWIT_ACTIVATION_VERSION 35, P2P_PORT 5024, proto floor 1700 /
    advertised 3301, SHARE_PERIOD 15, CHAIN_LENGTH 2880
  - v35 donation = forrestv P2PK (4104ffd0..ac, 67B); v36 = combined
    P2SH (23B) via get_donation_script() version switch
  - ADDRESS_VERSION 0x1e (D) / ADDRESS_P2SH_VERSION 0x3f (S)

Locks the conformance landed in the stack against silent regression.
Local build EXIT=0; dgb_share_test 5/5 PASS. Non-stacking lane off
stack tip; captured-block PoW + multi-algo accept-by-continuity
fixtures are a follow-up (see test/README.txt).

Author: frstrtr

src/impl/dgb/CMakeLists.txt

@@ -20,7 +20,7 @@ if(COIN_DGB)
   message(STATUS "c2pool: DGB Scrypt-only coin module enabled")
   add_subdirectory(coin)
   # add_subdirectory(daemon)
-  # add_subdirectory(test)
+  add_subdirectory(test)
 
   # dgb -- DGB Scrypt pool-layer OBJECT lib. Mirrors the ltc OBJECT lib
   # (src/impl/ltc/CMakeLists.txt): compiles the real NodeImpl translation unit

src/impl/dgb/test/CMakeLists.txt

@@ -0,0 +1,19 @@
+# DGB module tests. Mirrors src/impl/ltc/test/CMakeLists.txt — links the dgb
+# OBJECT lib (pool/share TU) so the share codec + consensus params are build-
+# verified into a test executable. Gated on BUILD_TESTING + GTest like the
+# sibling coins; registered via gtest_add_tests for the CI --target allowlist.
+if (BUILD_TESTING AND GTest_FOUND)
+    add_executable(dgb_share_test share_test.cpp)
+    target_link_libraries(dgb_share_test PRIVATE
+        GTest::gtest_main GTest::gtest
+        core dgb
+    )
+    # OBJECT-lib SCC direct-naming (#22/#39) — mirror the ltc test link set.
+    target_link_libraries(dgb_share_test PRIVATE
+        c2pool_payout c2pool_merged_mining c2pool_hashrate c2pool_storage
+        dgb_coin pool sharechain)
+
+    include(GoogleTest)
+    include_directories(${gtest_SOURCE_DIR}/include ${gtest_SOURCE_DIR})
+    gtest_add_tests(dgb_share_test "" AUTO)
+endif()

src/impl/dgb/test/share_test.cpp

@@ -0,0 +1,69 @@
+// DGB Scrypt-only coin module — share / consensus-identity fixtures (M3).
+// Mirrors src/impl/btc/test + src/impl/ltc/test. Locks the oracle-conformed
+// consensus + sharechain-identity params against frstrtr/p2pool-dgb-scrypt
+// (IDENTIFIER 4B62545B1A631AFE, PREFIX 1c0553f23ebfcffe). These are the params
+// adjudicated CONFORM at prescan-DGB (#131/#137/#141); this guards regressions.
+//
+// SCOPE (project_v36_dgb_scrypt_only): V36 validates SCRYPT shares only.
+// Scrypt-family wire format mirrors LTC; DGB-net identity lives in the params
+// asserted below, NOT in the share codec. Captured-block PoW fixtures + multi-
+// algo accept-by-continuity vectors are a follow-up slice (see README.txt).
+
+#include <gtest/gtest.h>
+
+#include <impl/dgb/config_pool.hpp>
+#include <impl/dgb/config_coin.hpp>
+#include <impl/dgb/share.hpp>
+
+// Sharechain-identity: the isolation primitives (PREFIX / IDENTIFIER) are the
+// per-coin namespacing boundary — they MUST stay byte-exact to the DGB oracle.
+TEST(DGB_share_test, OracleSharechainIdentity)
+{
+    EXPECT_EQ(dgb::PoolConfig::IDENTIFIER_HEX,     "4b62545b1a631afe");
+    EXPECT_EQ(dgb::PoolConfig::DEFAULT_PREFIX_HEX, "1c0553f23ebfcffe");
+    EXPECT_EQ(dgb::PoolConfig::TESTNET_IDENTIFIER_HEX, dgb::PoolConfig::IDENTIFIER_HEX);
+    EXPECT_EQ(dgb::PoolConfig::TESTNET_PREFIX_HEX,     dgb::PoolConfig::DEFAULT_PREFIX_HEX);
+}
+
+// Consensus / protocol params conformed to the oracle (networks/digibyte.py).
+TEST(DGB_share_test, OracleConsensusParams)
+{
+    EXPECT_EQ(dgb::PoolConfig::P2P_PORT,                   5024u);
+    EXPECT_EQ(dgb::PoolConfig::SEGWIT_ACTIVATION_VERSION,  35u);
+    EXPECT_EQ(dgb::PoolConfig::MINIMUM_PROTOCOL_VERSION,   1700u);
+    EXPECT_EQ(dgb::PoolConfig::ADVERTISED_PROTOCOL_VERSION, 3301u);
+    EXPECT_EQ(dgb::PoolConfig::SHARE_PERIOD,               15u);
+    EXPECT_EQ(dgb::PoolConfig::CHAIN_LENGTH,               2880u);
+}
+
+// v35 donation = forrestv P2PK (4104ffd0…ac, 65-byte pubkey push + CHECKSIG).
+// v36 donation = combined P2SH (23-byte). get_donation_script() switches on
+// share_version at the SEGWIT/merged boundary.
+TEST(DGB_share_test, OracleDonationScript)
+{
+    ASSERT_EQ(dgb::PoolConfig::DONATION_SCRIPT.size(), 67u);
+    EXPECT_EQ(dgb::PoolConfig::DONATION_SCRIPT.front(), 0x41);  // OP_PUSHBYTES_65
+    EXPECT_EQ(dgb::PoolConfig::DONATION_SCRIPT[1],      0x04);  // uncompressed pubkey tag
+    EXPECT_EQ(dgb::PoolConfig::DONATION_SCRIPT[2],      0xff);
+    EXPECT_EQ(dgb::PoolConfig::DONATION_SCRIPT[3],      0xd0);
+    EXPECT_EQ(dgb::PoolConfig::DONATION_SCRIPT.back(),  0xac);  // OP_CHECKSIG
+
+    EXPECT_EQ(dgb::PoolConfig::get_donation_script(35).size(), 67u);  // v35 P2PK
+    EXPECT_EQ(dgb::PoolConfig::get_donation_script(36).size(), 23u);  // v36 combined P2SH
+}
+
+// Address byte versions (D… P2PKH / S… P2SH) — DigiByte mainnet.
+TEST(DGB_share_test, AddressVersions)
+{
+    EXPECT_EQ(dgb::CoinParams::ADDRESS_VERSION,      0x1e);  // 30 — D prefix
+    EXPECT_EQ(dgb::CoinParams::ADDRESS_P2SH_VERSION, 0x3f);  // 63 — S prefix
+}
+
+// Share-codec link smoke: dgb::load_share is the Scrypt-family wire entrypoint.
+// Referencing it forces the dgb OBJECT-lib share TU to link into this test exe,
+// build-verifying the pool/share stack (#132→#142) end-to-end.
+TEST(DGB_share_test, LoadShareSymbolLinks)
+{
+    auto fn = static_cast<dgb::ShareType (*)(chain::RawShare&, NetService)>(&dgb::load_share);
+    EXPECT_NE(fn, nullptr);
+}