fix unit test - all pass

Tests/Unit/Sim/FittingTestHelper.h

@@ -40,8 +40,7 @@ public:
         sample.addLayer(Layer(material));
         sample.addLayer(Layer(material));
 
-        Detector2D detector(m_xmax - m_xmin, m_ymax - m_ymin, m_nx, m_ny, (m_xmin + m_xmax) / 2,
-                            (m_ymin + m_ymax) / 2);
+        Detector2D detector(m_nx, m_xmin, m_xmax, m_ny, m_ymin, m_ymax);
         std::unique_ptr<ScatteringSimulation> result(
             new ScatteringSimulation(Beam(1., 1., 0.), sample, detector));