[contextualprocess] Improve tests, fix off-by-one

- there's no string representation for a QVariantMap, so it
  won't be converted; in *debug* output it looks like there's a
  string there.
- off-by-one when diving into compound selectors, spotted by
  test, now fixed.

src/modules/contextualprocess/ContextualProcessJob.cpp

@@ -77,7 +77,7 @@ fetch( QString& value, QStringList& selector, int index, const QVariant& v )
     }
     const QVariantMap map = v.toMap();
     const QString& key = selector.at( index );
-    if ( index == selector.length() )
+    if ( index == selector.length() - 1)
     {
         value = map.value( key ).toString();
         return map.contains( key );

src/modules/contextualprocess/Tests.cpp

@@ -88,6 +88,8 @@ ContextualProcessTests::testProcessListSampleConfig()
 
 void ContextualProcessTests::testFetch()
 {
+    Logger::setupLogLevel( Logger::LOGVERBOSE );
+
     QVariantMap m;
     // Some keys without sub-map
     m.insert( QStringLiteral( "carrot" ), true );
@@ -150,7 +152,7 @@ void ContextualProcessTests::testFetch()
         ContextualProcessBinding b( QStringLiteral( "berries" ) );
         QString s;
         QVERIFY( b.fetch( gs, s ) );
-        QVERIFY( s.contains( QStringLiteral( "QVariant" ) ) );
+        QVERIFY( s.isEmpty() );  // No string representation
     }
     {
         // Compound lookup