use new c'tor in FitTests

Tests/Functional/Fitting/FitTests.cpp

@@ -70,15 +70,12 @@ const auto build_CylBA_MiniGISAS =
 
 const auto build_CylBA_Masked =
     [](const mumufit::Parameters& params) -> std::unique_ptr<ISimulation> {
-    double detector_distance(500.0);
-    double width(20.0), height(18.0);
-    FlatDetector detector(20u, width, 18u, height);
-    detector.setPerpendicularToSampleX(detector_distance, width / 2., 0.0);
+    Beam beam(Beam(1, 1.0 * Units::angstrom, 0.2 * deg));
+
+    FlatDetector detector(20u, 18u, 20., 18., beam, FlatDetector::X, 500.);
     // TODO restore detector.setRegionOfInterest(5.0, 6.0, 15.0, 12.0);
     detector.addMask(Rectangle(0.0, 0.0, 2.0, 2.0), true);
 
-    Beam beam(Beam(1, 1.0 * Units::angstrom, 0.2 * deg));
-
     std::unique_ptr<ScatteringSimulation> result(
         new ScatteringSimulation(beam, *build_CylBA(params), detector));