explicitly include <iostream>

instead of relying on relying that some header includes it...

tests/test_boprops_ad.cpp

@@ -37,6 +37,8 @@
 #include <opm/core/utility/parameters/ParameterGroup.hpp>
 
 #include <fstream>
+#include <iostream>
+
 
 struct SetupSimple {
     SetupSimple()

tests/test_scalar_mult.cpp

@@ -32,7 +32,7 @@
 #include <Eigen/Eigen>
 #include <Eigen/Sparse>
 
-
+#include <iostream>
 
 BOOST_AUTO_TEST_CASE(ScalarMultiplication)
 {

tests/test_span.cpp

@@ -30,6 +30,7 @@
 
 #include <boost/test/unit_test.hpp>
 
+#include <iostream>
 
 BOOST_AUTO_TEST_CASE(OneArgConstr)
 {

tests/test_syntax.cpp

@@ -8,9 +8,11 @@
 
 #include <opm/autodiff/AutoDiff.hpp>
 
-#include <cmath>
 #include <boost/test/unit_test.hpp>
 
+#include <cmath>
+#include <iostream>
+
 BOOST_AUTO_TEST_CASE(Initialisation)
 {
     typedef AutoDiff::Forward<double> AdFW;