message: add test read complex into real format
diff: @@ -39,6 +39,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  #include <sstream>
  +#include <ginkgo/core/base/exception.hpp>
  #include <ginkgo/core/base/lin_op.hpp>
  @@ -256,6 +257,22 @@ TEST(MtxReader, ReadsSparseComplexHermitianMtx)
  }
  +TEST(MtxReader, FailsWhenReadingSparseComplexMtxToRealMtx)
  +{
  + using cpx = std::complex<double>;
  + using tpl = gko::matrix_data<cpx, gko::int32>::nonzero_type;
  + std::istringstream iss(
  + "%%MatrixMarket matrix coordinate complex general\n"
  + "2 3 4\n"
  + "1 1 1.0 2.0\n"
  + "2 2 5.0 3.0\n"
  + "1 2 3.0 1.0\n"
  + "1 3 2.0 4.0\n");
  +
  + ASSERT_THROW((gko::read_raw<double, gko::int32>(iss)), gko::StreamError);
  +}
  +
  +
  TEST(MatrixData, WritesRealMatrixToMatrixMarketArray)
  {
  // clang-format off
  