Replaced the hash algorithm with classic FNV-1a with product folding.

- The seed is treated as a character to be appended to the string.

include/internal/catch_test_case_registry_impl.cpp

@@ -22,26 +22,27 @@ namespace Catch {
 
     namespace {
         struct TestHasher {
-            explicit TestHasher(Catch::SimplePcg32& rng_instance) {
-                basis = rng_instance();
-                basis <<= 32;
-                basis |= rng_instance();
-            }
+            using hash_t = uint64_t;
 
-            uint64_t basis;
+            explicit TestHasher(hash_t seed): m_seed{seed} {
+            }
 
-            uint32_t operator()(TestCase const& t) const {
-                // Modified FNV-1a hash
-                static constexpr uint64_t prime = 1099511628211;
-                uint64_t hash = basis;
-                for (const char c : t.name) {
+            hash_t operator()(TestCase const& t) const {
+                // FNV-1a hash with multiplication fold.
+                const hash_t prime = 1099511628211u;
+                hash_t hash = 14695981039346656037u;
+                for ( const char c : t.name ) {
                     hash ^= c;
                     hash *= prime;
                 }
+                hash ^= m_seed;
+                hash *= prime;
                 const auto low{ static_cast<uint32_t>( hash ) };
                 const auto high{ static_cast<uint32_t>( hash >> 32 ) };
-                return high * low;
+                return hash_t{ low * high };
             }
+        private:
+            hash_t m_seed;
         };
     } // end unnamed namespace
 
@@ -60,7 +61,7 @@ namespace Catch {
 
             case RunTests::InRandomOrder: {
                 seedRng( config );
-                TestHasher h( rng() );
+                TestHasher h{ config.rngSeed() };
 
                 using hashedTest = std::pair<uint32_t, TestCase const*>;
                 std::vector<hashedTest> indexed_tests;