updated changelog and fixed tests

com.unity.perception/CHANGELOG.md

 
 ### Added
 
+Added ScenarioConstants base class for all scenario constants objects
+
+Unique seeds per Sampler have been replaced with one global random seed configured via the ScenarioConstants of a Scenario
+
+Replaced ScenarioBase.GenerateRandomSeed() with ScenarioBase.NextRandomSeed()
+
+
+Removed ScenarioBase.GenerateRandomSeedFromIndex()
 
 ### Fixed
 

com.unity.perception/Tests/Runtime/Randomization/ParameterTests/StructParameterTests.cs

 using NUnit.Framework;
 using UnityEngine;
 using UnityEngine.Experimental.Perception.Randomization.Parameters;
+using UnityEngine.Experimental.Perception.Randomization.Scenarios;
 using Object = UnityEngine.Object;
 
 namespace RandomizationTests.ParameterTests
         public void Setup()
         {
             m_TestObject = new GameObject();
+            m_TestObject.AddComponent<FixedLengthScenario>();
             m_Tests = new BaseStructParameterTest[]
             {
                 new NumericParameterTest<bool>(new BooleanParameter()),
         }
 
         [Test]
-        public void EquivalentManagedAndNativeSamples()
+        public void CorrectNumberOfNativeSamplesAreGenerated()
         {
             foreach (var test in m_Tests)
                 test.GeneratesNativeSamples();

com.unity.perception/Tests/Runtime/Randomization/SamplerTests/SamplerTestsBase.cs

 using System;
 using NUnit.Framework;
 using Unity.Jobs;
+using UnityEngine;
+using Object = UnityEngine.Object;
 
 namespace RandomizationTests.SamplerTests
 {
         protected T m_BaseSampler;
         T m_Sampler;
+        GameObject m_ScenarioObj;
 
         static ScenarioBase activeScenario => ScenarioBase.activeScenario;
 
             m_Sampler = m_BaseSampler;
+            m_ScenarioObj = new GameObject("Scenario");
+            m_ScenarioObj.AddComponent<FixedLengthScenario>();
+        }
+
+        [TearDown]
+        public void TearDown()
+        {
+            Object.DestroyImmediate(m_ScenarioObj);
         }
 
         [Test]