diff --git a/Envelope_3/test/Envelope_3/spheres_test.C b/Envelope_3/test/Envelope_3/spheres_test.cpp
similarity index 100%
rename from Envelope_3/test/Envelope_3/spheres_test.C
rename to Envelope_3/test/Envelope_3/spheres_test.cpp
diff --git a/Envelope_3/test/Envelope_3/triangles_test.C b/Envelope_3/test/Envelope_3/triangles_test.cpp
similarity index 100%
rename from Envelope_3/test/Envelope_3/triangles_test.C
rename to Envelope_3/test/Envelope_3/triangles_test.cpp