Make Random*Generators be seedable

This is a necessary step to fix issue with combining multiple
random generators in one test case, with different section nesting.

src/CMakeLists.txt

@@ -222,6 +222,7 @@ set(IMPL_SOURCES
     ${SOURCES_DIR}/internal/catch_wildcard_pattern.cpp
     ${SOURCES_DIR}/internal/catch_xmlwriter.cpp
     ${SOURCES_DIR}/internal/catch_test_case_info_hasher.cpp
+    ${SOURCES_DIR}/generators/catch_generators_random.cpp
 )
 set(INTERNAL_FILES ${IMPL_SOURCES} ${INTERNAL_HEADERS})
 

src/catch2/generators/catch_generators_random.cpp

@@ -0,0 +1,13 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE_1_0.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+
+#include <catch2/generators/catch_generators_random.hpp>
+
+#include <catch2/internal/catch_context.hpp>
+
+std::uint32_t Catch::Generators::Detail::getSeed() { return sharedRng()(); }

src/catch2/generators/catch_generators_random.hpp

@@ -16,16 +16,21 @@
 
 namespace Catch {
 namespace Generators {
+namespace Detail {
+    // Returns a suitable seed for a random floating generator based off
+    // the primary internal rng. It does so by taking current value from
+    // the rng and returning it as the seed.
+    std::uint32_t getSeed();
+}
 
 template <typename Float>
 class RandomFloatingGenerator final : public IGenerator<Float> {
-    Catch::SimplePcg32& m_rng;
+    Catch::SimplePcg32 m_rng;
     std::uniform_real_distribution<Float> m_dist;
     Float m_current_number;
 public:
-
-    RandomFloatingGenerator(Float a, Float b):
-        m_rng(sharedRng()),
+    RandomFloatingGenerator( Float a, Float b, std::uint32_t seed ):
+        m_rng(seed),
         m_dist(a, b) {
         static_cast<void>(next());
     }
@@ -41,13 +46,12 @@ public:
 
 template <typename Integer>
 class RandomIntegerGenerator final : public IGenerator<Integer> {
-    Catch::SimplePcg32& m_rng;
+    Catch::SimplePcg32 m_rng;
     std::uniform_int_distribution<Integer> m_dist;
     Integer m_current_number;
 public:
-
-    RandomIntegerGenerator(Integer a, Integer b):
-        m_rng(sharedRng()),
+    RandomIntegerGenerator( Integer a, Integer b, std::uint32_t seed ):
+        m_rng(seed),
         m_dist(a, b) {
         static_cast<void>(next());
     }
@@ -68,7 +72,7 @@ std::enable_if_t<std::is_integral<T>::value && !std::is_same<T, bool>::value,
 GeneratorWrapper<T>>
 random(T a, T b) {
     return GeneratorWrapper<T>(
-        Catch::Detail::make_unique<RandomIntegerGenerator<T>>(a, b)
+        Catch::Detail::make_unique<RandomIntegerGenerator<T>>(a, b, Detail::getSeed())
     );
 }
 
@@ -77,7 +81,7 @@ std::enable_if_t<std::is_floating_point<T>::value,
 GeneratorWrapper<T>>
 random(T a, T b) {
     return GeneratorWrapper<T>(
-        Catch::Detail::make_unique<RandomFloatingGenerator<T>>(a, b)
+        Catch::Detail::make_unique<RandomFloatingGenerator<T>>(a, b, Detail::getSeed())
     );
 }
 

tests/SelfTest/IntrospectiveTests/GeneratorsImpl.tests.cpp

@@ -511,3 +511,26 @@ TEST_CASE( "Generator element stringification is cached",
 
     REQUIRE( generator.stringificationCalls() == 1 );
 }
+
+TEST_CASE( "Random generators can be seeded", "[generators][approvals]" ) {
+    SECTION( "Integer generator" ) {
+        using Catch::Generators::RandomIntegerGenerator;
+        RandomIntegerGenerator<int> rng1( 0, 100, 0x1234 ),
+                                    rng2( 0, 100, 0x1234 );
+
+        for ( size_t i = 0; i < 10; ++i ) {
+            REQUIRE( rng1.get() == rng2.get() );
+            rng1.next(); rng2.next();
+        }
+    }
+    SECTION("Float generator") {
+        using Catch::Generators::RandomFloatingGenerator;
+        RandomFloatingGenerator<double> rng1( 0., 100., 0x1234 ),
+                                        rng2( 0., 100., 0x1234 );
+        for ( size_t i = 0; i < 10; ++i ) {
+            REQUIRE( rng1.get() == rng2.get() );
+            rng1.next();
+            rng2.next();
+        }
+    }
+}