diff --git a/include/mrdox/Config.hpp b/include/mrdox/Config.hpp
index 5a690affb..5e313aaff 100644
--- a/include/mrdox/Config.hpp
+++ b/include/mrdox/Config.hpp
@@ -82,7 +82,8 @@ setupContext(
 
 llvm::Error
 doMapping(
-    Config& cfg);
+    Corpus& corpus,
+    Config const& cfg);
 
 /** Build the internal index of the program under analysis.
 
@@ -90,8 +91,8 @@ doMapping(
 */
 llvm::Error
 buildIndex(
-    Config const& cfg,
-    Corpus& corpus);
+    Corpus& corpus,
+    Config const& cfg);
 
 } // mrdox
 } // clang
diff --git a/source/lib/ClangDoc.cpp b/source/lib/ClangDoc.cpp
index 9406e6956..e8980cb18 100644
--- a/source/lib/ClangDoc.cpp
+++ b/source/lib/ClangDoc.cpp
@@ -25,19 +25,16 @@ namespace mrdox {
 
 namespace {
 
-// VFALCO It looks like each created action needs
-//        its own copy of the Config?
-//        Maybe because of concurrency.
-
 //------------------------------------------------
 
 struct action
     : public clang::ASTFrontendAction
 {
-    explicit
     action(
-        Config& cfg)
-        : cfg(cfg)
+        Corpus& corpus,
+        Config const& cfg) noexcept
+        : corpus_(corpus)
+        , cfg_(cfg)
     {
     }
 
@@ -46,11 +43,12 @@ struct action
         clang::CompilerInstance& Compiler,
         llvm::StringRef InFile) override
     {
-        return std::make_unique<MapASTVisitor>(cfg);
+        return std::make_unique<MapASTVisitor>(corpus_, cfg_);
     }
 
 private:
-    Config& cfg;
+    Corpus& corpus_;
+    Config const& cfg_;
 };
 
 //------------------------------------------------
@@ -58,20 +56,23 @@ struct action
 struct factory
     : public tooling::FrontendActionFactory
 {
-    explicit
     factory(
-        Config& cfg)
-        : cfg(cfg)
+        Corpus& corpus,
+        Config const& cfg) noexcept
+        : corpus_(corpus)
+        , cfg_(cfg)
     {
     }
 
     std::unique_ptr<FrontendAction>
     create() override
     {
-        return std::make_unique<action>(cfg);
+        return std::make_unique<action>(corpus_, cfg_);
     }
-        
-    Config& cfg;
+
+private:
+    Corpus& corpus_;
+    Config const& cfg_;
 };
 
 } // (anon)
@@ -81,18 +82,20 @@ struct factory
 std::unique_ptr<
     clang::FrontendAction>
 makeFrontendAction(
-    Config& cfg)
+    Corpus& corpus,
+    Config const& cfg)
 {
-    return std::make_unique<action>(cfg);
+    return std::make_unique<action>(corpus, cfg);
 }
 
 std::unique_ptr<
     tooling::FrontendActionFactory>
 newMapperActionFactory(
-    Config& cfg)
+    Corpus& corpus,
+    Config const& cfg)
 {
-    return std::make_unique<factory>(cfg);
+    return std::make_unique<factory>(corpus, cfg);
 }
 
-} // namespace mrdox
-} // namespace clang
+} // mrdox
+} // clang
diff --git a/source/lib/ClangDoc.h b/source/lib/ClangDoc.h
index 139d4ae2d..57b2cdd64 100644
--- a/source/lib/ClangDoc.h
+++ b/source/lib/ClangDoc.h
@@ -29,12 +29,14 @@ namespace mrdox {
 std::unique_ptr<
     clang::FrontendAction>
 makeFrontendAction(
-    Config& cfg);
+    Corpus& corpus,
+    Config const& cfg);
 
 std::unique_ptr<
     tooling::FrontendActionFactory>
 newMapperActionFactory(
-    Config& cfg);
+    Corpus& corpus,
+    Config const& cfg);
 
 } // namespace mrdox
 } // namespace clang
diff --git a/source/lib/Config.cpp b/source/lib/Config.cpp
index 2f3aa5191..f02d842f2 100644
--- a/source/lib/Config.cpp
+++ b/source/lib/Config.cpp
@@ -197,14 +197,15 @@ setupContext(
 
 llvm::Error
 doMapping(
-    Config& cfg)
+    Corpus& corpus,
+    Config const& cfg)
 {
     //
     // Mapping phase
     //
     llvm::outs() << "Mapping declarations\n";
     auto Err = cfg.Executor->execute(
-        newMapperActionFactory(cfg),
+        newMapperActionFactory(corpus, cfg),
         cfg.ArgAdjuster);
     if(Err)
     {
@@ -225,8 +226,8 @@ doMapping(
 
 llvm::Error
 buildIndex(
-    Config const& cfg,
-    Corpus& corpus)
+    Corpus& corpus,
+    Config const& cfg)
 {
     // Collect values into output by key.
     // In ToolResults, the Key is the hashed USR and the value is the
diff --git a/source/lib/Error.hpp b/source/lib/Error.hpp
new file mode 100644
index 000000000..79140174e
--- /dev/null
+++ b/source/lib/Error.hpp
@@ -0,0 +1,23 @@
+//
+// This is a derivative work. originally part of the LLVM Project.
+// Licensed under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// Copyright (c) 2023 Vinnie Falco (vinnie.falco@gmail.com)
+//
+// Official repository: https://github.com/cppalliance/mrdox
+//
+
+#ifndef MRDOX_SOURCE_ERROR_HPP
+#define MRDOX_SOURCE_ERROR_HPP
+
+#include <llvm/Support/Error.h>
+
+namespace clang {
+namespace mrdox {
+
+} // mrdox
+} // clang
+
+#endif
diff --git a/source/lib/Mapper.cpp b/source/lib/Mapper.cpp
index ce1b54892..7f9582bc5 100644
--- a/source/lib/Mapper.cpp
+++ b/source/lib/Mapper.cpp
@@ -11,6 +11,7 @@
 
 #include "Mapper.h"
 #include "BitcodeWriter.h"
+#include "Error.hpp"
 #include "Serialize.h"
 #ifdef _MSC_VER
 #pragma warning(push)
@@ -52,18 +53,20 @@ mapDecl(T const* D)
         return true;
     bool IsFileInRootDir;
     llvm::SmallString<128> File =
-        getFile(D, D->getASTContext(), cfg.SourceRoot, IsFileInRootDir);
+        getFile(D, D->getASTContext(), cfg_.SourceRoot, IsFileInRootDir);
     auto I = serialize::emitInfo(D, getComment(D, D->getASTContext()),
         getLine(D, D->getASTContext()), File,
-        IsFileInRootDir, cfg.PublicOnly);
+        IsFileInRootDir, cfg_.PublicOnly);
 
     // A null in place of I indicates that the serializer is skipping this decl
     // for some reason (e.g. we're only reporting public decls).
     if (I.first)
-        cfg.ECtx->reportResult(llvm::toHex(llvm::toStringRef(I.first->USR)),
+        cfg_.ECtx->reportResult(
+            llvm::toHex(llvm::toStringRef(I.first->USR)),
             serialize::serialize(I.first));
     if (I.second)
-        cfg.ECtx->reportResult(llvm::toHex(llvm::toStringRef(I.second->USR)),
+        cfg_.ECtx->reportResult(
+            llvm::toHex(llvm::toStringRef(I.second->USR)),
             serialize::serialize(I.second));
     return true;
 }
diff --git a/source/lib/Mapper.h b/source/lib/Mapper.h
index 057c7438b..65727a42d 100644
--- a/source/lib/Mapper.h
+++ b/source/lib/Mapper.h
@@ -38,8 +38,10 @@ class MapASTVisitor
 public:
     explicit
     MapASTVisitor(
+        Corpus& corpus,
         Config const& cfg)
-        : cfg(cfg)
+        : corpus_(corpus)
+        , cfg_(cfg)
     {
     }
 
@@ -73,7 +75,8 @@ class MapASTVisitor
         NamedDecl const* D,
         ASTContext const& Context) const;
 
-    Config const& cfg;
+    Corpus& corpus_;
+    Config const& cfg_;
 };
 
 } // mrdox
diff --git a/source/lib/Representation.h b/source/lib/Representation.h
index baf8ecfff..100b4e5f8 100644
--- a/source/lib/Representation.h
+++ b/source/lib/Representation.h
@@ -111,20 +111,40 @@ struct CommentInfo
         Children; // List of child comments for this CommentInfo.
 };
 
-struct Reference {
+struct Reference
+{
     // This variant (that takes no qualified name parameter) uses the Name as the
     // QualName (very useful in unit tests to reduce verbosity). This can't use an
     // empty string to indicate the default because we need to accept the empty
     // string as a valid input for the global namespace (it will have
     // "GlobalNamespace" as the name, but an empty QualName).
-    Reference(SymbolID USR = SymbolID(), StringRef Name = StringRef(),
+    Reference(
+        SymbolID USR = SymbolID(),
+        StringRef Name = StringRef(),
         InfoType IT = InfoType::IT_default)
-        : USR(USR), Name(Name), QualName(Name), RefType(IT) {}
-    Reference(SymbolID USR, StringRef Name, InfoType IT, StringRef QualName,
+        : USR(USR)
+        , Name(Name)
+        , QualName(Name)
+        , RefType(IT)
+    {
+    }
+
+    Reference(
+        SymbolID USR,
+        StringRef Name,
+        InfoType IT,
+        StringRef QualName,
         StringRef Path = StringRef())
-        : USR(USR), Name(Name), QualName(QualName), RefType(IT), Path(Path) {}
+        : USR(USR)
+        , Name(Name)
+        , QualName(QualName)
+        , RefType(IT)
+        , Path(Path)
+    {
+    }
 
-    bool operator==(const Reference& Other) const {
+    bool operator==(const Reference& Other) const
+    {
         return std::tie(USR, Name, QualName, RefType) ==
             std::tie(Other.USR, Other.Name, QualName, Other.RefType);
     }
@@ -151,10 +171,10 @@ struct Reference {
     SmallString<16> QualName;
 
     InfoType RefType = InfoType::IT_default; // Indicates the type of this
-    // Reference (namespace, record,
-    // function, enum, default).
-// Path of directory where the clang-doc generated file will be saved
-// (possibly unresolved)
+    // Reference (namespace, record, function, enum, default).
+
+    // Path of directory where the mrdox generated file will be saved
+    // (possibly unresolved)
     llvm::SmallString<128> Path;
 };
 
@@ -215,7 +235,8 @@ struct AccessScope
 };
 
 // A base struct for TypeInfos
-struct TypeInfo {
+struct TypeInfo
+{
     TypeInfo() = default;
     TypeInfo(const Reference& R) : Type(R) {}
 
diff --git a/source/lib/XML.cpp b/source/lib/XML.cpp
index b20cedfc3..bbca33f24 100644
--- a/source/lib/XML.cpp
+++ b/source/lib/XML.cpp
@@ -564,13 +564,17 @@ renderCodeAsXML(
     Config const& cfg)
 {
     std::unique_ptr<ASTUnit> astUnit =
-    clang::tooling::buildASTFromCodeWithArgs(cppCode, {});
-    MapASTVisitor visitor(cfg);
-    visitor.HandleTranslationUnit(astUnit->getASTContext());
+        clang::tooling::buildASTFromCodeWithArgs(cppCode, {});
     Corpus corpus;
-    if(llvm::Error err = buildIndex(cfg, corpus))
+    MapASTVisitor visitor(corpus, cfg);
+    visitor.HandleTranslationUnit(astUnit->getASTContext());
+    if(llvm::Error err = buildIndex(corpus, cfg))
         return ! err;
-    return XMLGenerator(cfg).render(xml, corpus, cfg);
+    bool success = XMLGenerator(cfg).render(xml, corpus, cfg);
+    // VFALCO oops, cfg.Executor->getToolResults()
+    //              holds information from the previous corpus...
+    //cfg.Executor->getToolResults()->
+    return success;
 }
 
 //------------------------------------------------
diff --git a/source/mrdox/ToolMain.cpp b/source/mrdox/ToolMain.cpp
index f6b3c8456..800d844e6 100644
--- a/source/mrdox/ToolMain.cpp
+++ b/source/mrdox/ToolMain.cpp
@@ -85,8 +85,10 @@ main(int argc, const char** argv)
         return EXIT_FAILURE;
     }
 
+    clang::mrdox::Corpus corpus;
+
     // Extract the AST first
-    if(llvm::Error err = doMapping(cfg))
+    if(llvm::Error err = doMapping(corpus, cfg))
     {
         llvm::errs() <<
             toString(std::move(err)) << "\n";
@@ -95,8 +97,7 @@ main(int argc, const char** argv)
 
     // Build the internal representation of
     // the C++ declarations to be documented.
-    clang::mrdox::Corpus corpus;
-    if(llvm::Error err = buildIndex(cfg, corpus))
+    if(llvm::Error err = buildIndex(corpus, cfg))
     {
         llvm::errs() <<
             toString(std::move(err)) << "\n";
diff --git a/source/tests/TestMain.cpp b/source/tests/TestMain.cpp
index 5f6569f33..7100f0977 100644
--- a/source/tests/TestMain.cpp
+++ b/source/tests/TestMain.cpp
@@ -20,6 +20,7 @@
 #include <llvm/Support/MemoryBuffer.h>
 #include <llvm/Support/Path.h>
 #include <llvm/Support/raw_ostream.h>
+#include <atomic>
 #include <cstdlib>
 
 // VFALCO GARBAGE
@@ -35,6 +36,11 @@ namespace mrdox {
 
 namespace {
 
+void
+testDir()
+{
+}
+
 //------------------------------------------------
 
 int
@@ -59,12 +65,15 @@ do_main(int argc, const char** argv)
         return EXIT_FAILURE;
     }
 
+    std::atomic<bool> gotFailure = false;
+
     std::string xml;
     for(int i = 1; i < argc; ++i)
     {
         std::error_code ec;
         llvm::SmallString<256> dir(argv[i]);
         path::remove_dots(dir, true);
+        fs::recursive_directory_iterator const end{};
         fs::recursive_directory_iterator iter(dir, ec, false);
         if(ec)
         {
@@ -73,71 +82,89 @@ do_main(int argc, const char** argv)
                 dir << "\"\n";
             return EXIT_FAILURE;
         }
-        auto const& name = iter->path();
-        llvm::SmallString<128> cppPath(name);
-        llvm::SmallString<128> xmlPath(name);
-        path::remove_dots(cppPath, true);
-        path::remove_dots(xmlPath, true);
-        if(path::extension(name).equals_insensitive(".cpp"))
+        while(iter != end)
         {
-            if(! fs::is_regular_file(name))
             {
-                llvm::errs() <<
-                    "invalid file: \"" << name << "\"\n";
-                return EXIT_FAILURE;
+                auto const& name = iter->path();
+                llvm::SmallString<128> cppPath(name);
+                llvm::SmallString<128> xmlPath(name);
+                path::remove_dots(cppPath, true);
+                path::remove_dots(xmlPath, true);
+                if(path::extension(name).equals_insensitive(".cpp"))
+                {
+                    if(! fs::is_regular_file(name))
+                    {
+                        llvm::errs() <<
+                            "invalid file: \"" << name << "\"\n";
+                        return EXIT_FAILURE;
+                    }
+                    path::replace_extension(xmlPath, "xml");
+                    if( ! fs::exists(xmlPath) ||
+                        ! fs::is_regular_file(xmlPath))
+                    {
+                        llvm::errs() <<
+                            "missing or invalid file: \"" << xmlPath << "\"\n";
+                        return EXIT_FAILURE;
+                    }
+                }
+                else if(path::extension(name).equals_insensitive(".xml"))
+                {
+                    path::replace_extension(cppPath, "cpp");
+                    if( ! fs::exists(cppPath) ||
+                        ! fs::is_regular_file(cppPath))
+                    {
+                        llvm::errs() <<
+                            "missing or invalid file: \"" << cppPath << "\"\n";
+                        return EXIT_FAILURE;
+                    }
+
+                    // don't process the same test twice
+                    goto loop;
+                }
+                else
+                {
+                    // not .cpp or .xml
+                    goto loop;
+                }
+
+                llvm::StringRef cppCode;
+                auto cppResult = llvm::MemoryBuffer::getFile(cppPath, true);
+                if(! cppResult)
+                {
+                    llvm::errs() <<
+                        cppResult.getError().message() << ": \"" << xmlPath << "\"\n";
+                    return EXIT_FAILURE;
+                }
+                cppCode = cppResult->get()->getBuffer();
+
+                llvm::StringRef expectedXml;
+                auto xmlResult = llvm::MemoryBuffer::getFile(xmlPath, true);
+                if(! xmlResult)
+                {
+                    llvm::errs() <<
+                        xmlResult.getError().message() << ": \"" << xmlPath << "\"\n";
+                    return EXIT_FAILURE;
+                }
+                expectedXml = xmlResult->get()->getBuffer();
+
+                if(! renderCodeAsXML(xml, cppCode, cfg))
+                    return EXIT_FAILURE;
+
+                if(xml != expectedXml)
+                {
+                    gotFailure = true;
+                    llvm::errs() <<
+                        "Failed: \"" << xmlPath << "\", got\n" <<
+                        xml;
+                }
             }
-            path::replace_extension(xmlPath, "xml");
-            if( ! fs::exists(xmlPath) ||
-                ! fs::is_regular_file(xmlPath))
-            {
-                llvm::errs() <<
-                    "missing or invalid file: \"" << xmlPath << "\"\n";
-                return EXIT_FAILURE;
-            }
-        }
-        else if(path::extension(name).equals_insensitive(".xml"))
-        {
-            path::replace_extension(cppPath, "cpp");
-            if( ! fs::exists(cppPath) ||
-                ! fs::is_regular_file(cppPath))
-            {
-                llvm::errs() <<
-                    "missing or invalid file: \"" << cppPath << "\"\n";
-                return EXIT_FAILURE;
-            }
-
-            // don't process the same test twice
-            continue;
-        }
-
-        llvm::StringRef cppCode;
-        auto cppResult = llvm::MemoryBuffer::getFile(cppPath, true);
-        if(! cppResult)
-        {
-            llvm::errs() <<
-                cppResult.getError().message() << ": \"" << xmlPath << "\"\n";
-            return EXIT_FAILURE;
+        loop:
+            iter.increment(ec);
         }
-        cppCode = cppResult->get()->getBuffer();
-
-        llvm::StringRef expectedXml;
-        auto xmlResult = llvm::MemoryBuffer::getFile(xmlPath, true);
-        if(! xmlResult)
-        {
-            llvm::errs() <<
-                xmlResult.getError().message() << ": \"" << xmlPath << "\"\n";
-            return EXIT_FAILURE;
-        }
-        expectedXml = xmlResult->get()->getBuffer();
-
-        if(! renderCodeAsXML(xml, cppCode, cfg))
-            return EXIT_FAILURE;
-
-        if(xml != expectedXml)
-            llvm::errs() <<
-                "Failed: \"" << xmlPath << "\"\n";
     }
 
+    if(gotFailure)
+        return EXIT_FAILURE;
     return EXIT_SUCCESS;
 }
 
diff --git a/testfiles/bare/ns.cpp b/testfiles/bare/ns.cpp
new file mode 100644
index 000000000..fe71f4004
--- /dev/null
+++ b/testfiles/bare/ns.cpp
@@ -0,0 +1 @@
+namespace N {}
diff --git a/testfiles/bare/ns.xml b/testfiles/bare/ns.xml
new file mode 100644
index 000000000..792e15c77
--- /dev/null
+++ b/testfiles/bare/ns.xml
@@ -0,0 +1,2 @@
+<ns n="N">
+ </ns>