fix unit tests after mixed up statics initialization

Author: Sergey Kanzhelev

src/OpenCensus/Impl/Trace/Config/TraceParams.cs

@@ -22,16 +22,14 @@ namespace OpenCensus.Trace.Config
     public sealed class TraceParams : ITraceParams
     {
         public static readonly ITraceParams DEFAULT =
-            new TraceParams(DEFAULT_SAMPLER, DEFAULT_SPAN_MAX_NUM_ATTRIBUTES, DEFAULT_SPAN_MAX_NUM_ANNOTATIONS, DEFAULT_SPAN_MAX_NUM_MESSAGE_EVENTS, DEFAULT_SPAN_MAX_NUM_LINKS);
+            new TraceParams(Samplers.GetProbabilitySampler(DefaultProbability), DEFAULT_SPAN_MAX_NUM_ATTRIBUTES, DEFAULT_SPAN_MAX_NUM_ANNOTATIONS, DEFAULT_SPAN_MAX_NUM_MESSAGE_EVENTS, DEFAULT_SPAN_MAX_NUM_LINKS);
 
         private const double DefaultProbability = 1e-4;
         private const int DEFAULT_SPAN_MAX_NUM_ATTRIBUTES = 32;
         private const int DEFAULT_SPAN_MAX_NUM_ANNOTATIONS = 32;
         private const int DEFAULT_SPAN_MAX_NUM_MESSAGE_EVENTS = 128;
         private const int DEFAULT_SPAN_MAX_NUM_LINKS = 128;
 
-        private static readonly ISampler DEFAULT_SAMPLER = Samplers.GetProbabilitySampler(DefaultProbability);
-
         internal TraceParams(ISampler sampler, int maxNumberOfAttributes, int maxNumberOfAnnotations, int maxNumberOfMessageEvents, int maxNumberOfLinks)
         {
             if (maxNumberOfAttributes <= 0)

test/OpenCensus.Tests/OpenCensus.Tests.csproj

@@ -16,10 +16,20 @@
     <CodeAnalysisRuleSet>$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildProjectDirectory), 'OpenCensus.sln'))\build\OpenCensus.test.ruleset</CodeAnalysisRuleSet>
   </PropertyGroup>
 
+  <ItemGroup>
+    <None Remove="xunit.runner.json" />
+  </ItemGroup>
+
   <ItemGroup>
     <AdditionalFiles Include="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildProjectDirectory), 'OpenCensus.sln'))\build\stylecop.json" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Content Include="xunit.runner.json">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\..\src\OpenCensus\OpenCensus.csproj" />
   </ItemGroup>

test/OpenCensus.Tests/xunit.runner.json

@@ -0,0 +1,4 @@
+{
+  "maxParallelThreads": 1,
+  "parallelizeTestCollections": false
+}