Combined test: append mode and weird iteration order

Author: franzpoeschel

test/SerialIOTest.cpp

@@ -5069,7 +5069,25 @@ void append_mode(
         }
 
         writeSomeIterations(
-            write.writeIterations(), std::vector< uint64_t >{ 4, 3 } );
+            write.writeIterations(), std::vector< uint64_t >{ 4, 3, 10 } );
+        write.flush();
+    }
+    {
+        Series write( filename, Access::APPEND, jsonConfig );
+        if( variableBased )
+        {
+            write.setIterationEncoding( IterationEncoding::variableBased );
+        }
+        if( write.backend() == "ADIOS1" )
+        {
+            REQUIRE_THROWS_AS(
+                write.flush(), error::OperationUnsupportedInBackend );
+            // destructor will be noisy now
+            return;
+        }
+
+        writeSomeIterations(
+            write.writeIterations(), std::vector< uint64_t >{ 7, 1, 11 } );
         write.flush();
     }
     {
@@ -5079,26 +5097,28 @@ void append_mode(
             // in variable-based encodings, iterations are not parsed ahead of
             // time but as they go
             unsigned counter = 0;
+            uint64_t iterationOrder[] = { 0, 1, 2, 3, 4, 10, 7, 11 };
             for( auto iteration : read.readIterations() )
             {
-                REQUIRE( iteration.iterationIndex == counter );
+                REQUIRE(
+                    iteration.iterationIndex == iterationOrder[ counter ] );
                 ++counter;
             }
-            REQUIRE( counter == 5 );
+            REQUIRE( counter == 8 );
             // Cannot do listSeries here because the Series is already drained
             REQUIRE_THROWS_AS(
                 helper::listSeries( read ), error::WrongAPIUsage );
         }
         else
         {
-            REQUIRE( read.iterations.size() == 5 );
+            REQUIRE( read.iterations.size() == 8 );
             /*
-            * Roadmap: for now, reading this should work by ignoring the last
-            * duplicate iteration.
-            * After merging https://github.com/openPMD/openPMD-api/pull/949, we
-            * should see both instances when reading.
-            * Final goal: Read only the last instance.
-            */
+             * Roadmap: for now, reading this should work by ignoring the last
+             * duplicate iteration.
+             * After merging https://github.com/openPMD/openPMD-api/pull/949, we
+             * should see both instances when reading.
+             * Final goal: Read only the last instance.
+             */
             helper::listSeries( read );
         }
     }