From d87e551efabb32bb08cd9abff51bb0c47fe6081c Mon Sep 17 00:00:00 2001
From: Phil Nash <github@philnash.me>
Date: Thu, 2 Jul 2015 23:02:35 +0100
Subject: [PATCH] reseeds rng before each test case and provides access to seed
 through Catch::rngSeed() function

---
 include/catch_runner.hpp                           | 2 +-
 include/internal/catch_common.h                    | 5 +++++
 include/internal/catch_common.hpp                  | 8 ++++++++
 include/internal/catch_runner_impl.hpp             | 2 ++
 include/internal/catch_test_case_registry_impl.hpp | 2 ++
 5 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/catch_runner.hpp b/include/catch_runner.hpp
index 3a674148..18754483 100644
--- a/include/catch_runner.hpp
+++ b/include/catch_runner.hpp
@@ -198,7 +198,7 @@ namespace Catch {
                 if( m_configData.filenamesAsTags )
                     applyFilenamesAsTags();
                 
-                std::srand( m_configData.rngSeed );
+                seedRng( *m_config );
 
                 Runner runner( m_config );
 
diff --git a/include/internal/catch_common.h b/include/internal/catch_common.h
index 9f07e47c..cec7eba5 100644
--- a/include/internal/catch_common.h
+++ b/include/internal/catch_common.h
@@ -22,6 +22,8 @@
 #include "catch_compiler_capabilities.h"
 
 namespace Catch {
+    
+    struct IConfig;
 
     class NonCopyable {
 #ifdef CATCH_CONFIG_CPP11_GENERATED_METHODS
@@ -109,6 +111,9 @@ namespace Catch {
 
     void throwLogicError( std::string const& message, SourceLineInfo const& locationInfo );
 
+    void seedRng( IConfig const& config );
+    unsigned int rngSeed();
+    
     // Use this in variadic streaming macros to allow
     //    >> +StreamEndStop
     // as well as
diff --git a/include/internal/catch_common.hpp b/include/internal/catch_common.hpp
index 8a42d0a0..69a64ad1 100644
--- a/include/internal/catch_common.hpp
+++ b/include/internal/catch_common.hpp
@@ -82,6 +82,14 @@ namespace Catch {
         return line < other.line || ( line == other.line  && file < other.file );
     }
 
+    void seedRng( IConfig const& config ) {
+        if( config.rngSeed() != 0 )
+            std::srand( config.rngSeed() );
+    }
+    unsigned int rngSeed() {
+        return getCurrentContext().getConfig()->rngSeed();
+    }
+
     std::ostream& operator << ( std::ostream& os, SourceLineInfo const& info ) {
 #ifndef __GNUG__
         os << info.file << "(" << info.line << ")";
diff --git a/include/internal/catch_runner_impl.hpp b/include/internal/catch_runner_impl.hpp
index 98f3dfd1..073f78d3 100644
--- a/include/internal/catch_runner_impl.hpp
+++ b/include/internal/catch_runner_impl.hpp
@@ -259,6 +259,8 @@ namespace Catch {
                 m_lastAssertionInfo = AssertionInfo( "TEST_CASE", testCaseInfo.lineInfo, "", ResultDisposition::Normal );
                 TestCaseTracker::Guard guard( *m_testCaseTracker );
 
+                seedRng( *m_config );
+                
                 Timer timer;
                 timer.start();
                 if( m_reporter->getPreferences().shouldRedirectStdOut ) {
diff --git a/include/internal/catch_test_case_registry_impl.hpp b/include/internal/catch_test_case_registry_impl.hpp
index 21165a30..b25ed9a2 100644
--- a/include/internal/catch_test_case_registry_impl.hpp
+++ b/include/internal/catch_test_case_registry_impl.hpp
@@ -90,6 +90,8 @@ namespace Catch {
                     break;
                 case RunTests::InRandomOrder:
                 {
+                    seedRng( config );
+                    
                     RandomNumberGenerator rng;
                     std::random_shuffle( matchingTestCases.begin(), matchingTestCases.end(), rng );
                 }