fuzz: Clarify that only SeedRandomStateForTest(SeedRand::ZEROS) is allowed

Author: MarcoFalke

src/test/util/random.cpp

@@ -39,6 +39,9 @@ void SeedRandomStateForTest(SeedRand seedtype)
     }();
 
     g_seeded_g_prng_zero = seedtype == SeedRand::ZEROS;
+    if constexpr (G_FUZZING) {
+        Assert(g_seeded_g_prng_zero); // Only SeedRandomStateForTest(SeedRand::ZEROS) is allowed in fuzz tests
+    }
     const uint256& seed{seedtype == SeedRand::FIXED_SEED ? ctx_seed : uint256::ZERO};
     LogInfo("Setting random seed for current tests to %s=%s\n", RANDOM_CTX_SEED, seed.GetHex());
     MakeRandDeterministicDANGEROUS(seed);

src/test/util/setup_common.cpp

@@ -108,6 +108,9 @@ static void ExitFailure(std::string_view str_err)
 BasicTestingSetup::BasicTestingSetup(const ChainType chainType, TestOpts opts)
     : m_args{}
 {
+    if constexpr (!G_FUZZING) {
+        SeedRandomForTest(SeedRand::FIXED_SEED);
+    }
     m_node.shutdown_signal = &m_interrupt;
     m_node.shutdown_request = [this]{ return m_interrupt(); };
     m_node.args = &gArgs;
@@ -139,8 +142,6 @@ BasicTestingSetup::BasicTestingSetup(const ChainType chainType, TestOpts opts)
         }
     }
 
-    SeedRandomForTest(SeedRand::FIXED_SEED);
-
     const std::string test_name{G_TEST_GET_FULL_NAME ? G_TEST_GET_FULL_NAME() : ""};
     if (!m_node.args->IsArgSet("-testdatadir")) {
         // To avoid colliding with a leftover prior datadir, and to allow