Mark some single-argument constructors explicit

src/test/core/Stoppable_test.cpp

@@ -400,7 +400,7 @@ class Stoppable_test
         C c_;
         Stoppable_test& test_;
     public:
-        Root(Stoppable_test& test)
+        explicit Root(Stoppable_test& test)
             : RootStoppable("R")
             , a_(&A::run, std::make_unique<A>(*this, test))
             , b_(*this, test)

src/test/core/TerminateHandler_test.cpp

@@ -36,7 +36,7 @@ private:
     class CerrRedirect
     {
     public:
-        CerrRedirect (std::stringstream& sStream)
+        explicit CerrRedirect (std::stringstream& sStream)
         : old_ (std::cerr.rdbuf (sStream.rdbuf()))
         { }
 
@@ -53,7 +53,7 @@ private:
     class ThreadNameGuard
     {
     public:
-        ThreadNameGuard (std::string const& newName)
+        explicit ThreadNameGuard (std::string const& newName)
         : old_ (beast::getCurrentThreadName ())
         {
             beast::setCurrentThreadName (newName);