jfjoch_tests: Add more tests

tests/DiffractionGeometryTest.cpp

@@ -471,4 +471,56 @@ TEST_CASE("ResPhiToPxl_poni_rot") {
     out = geom.ResPhiToPxl(2.0, 0.7567);
     CHECK(geom.PxlToRes(out.first, out.second) == Catch::Approx(2.0));
     CHECK(fabs(geom.Phi_rad(out.first, out.second) - 0.7567) < 0.001 );
+}
+
+TEST_CASE("DiffractionGeometry_DetectorToRecip_RecipToDetector_tilted") {
+    // Verify roundtrip consistency with non-zero rot1/rot2
+    DiffractionGeometry geom;
+    geom.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(150)
+        .PixelSize_mm(0.075).Wavelength_A(1.0)
+        .PoniRot1_rad(0.05).PoniRot2_rad(-0.03);
+
+    // Test multiple points across the detector
+    std::vector<std::pair<float, float>> test_points = {
+        {500, 500}, {1500, 500}, {500, 1500}, {1500, 1500},
+        {800, 1200}, {1200, 800}, {300, 1700}, {1700, 300}
+    };
+
+    for (const auto& [x, y] : test_points) {
+        Coord recip = geom.DetectorToRecip(x, y);
+        auto [proj_x, proj_y] = geom.RecipToDector(recip);
+
+        CHECK(proj_x == Catch::Approx(x).margin(0.001));
+        CHECK(proj_y == Catch::Approx(y).margin(0.001));
+    }
+}
+
+TEST_CASE("DiffractionGeometry_PONI_matrix_consistency") {
+    // Verify that the PONI rotation matrix gives consistent results
+    // when used for both forward and inverse transformations
+    DiffractionGeometry geom;
+    geom.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(100)
+        .PixelSize_mm(0.075).Wavelength_A(1.0)
+        .PoniRot1_rad(0.04).PoniRot2_rad(-0.025);
+
+    const auto& poni_rot = geom.GetPoniRotMatrix();
+    const auto poni_rot_T = poni_rot.transpose();
+
+    // Test: poni_rot * poni_rot^T should be identity (orthogonal matrix)
+    for (int i = 0; i < 3; ++i) {
+        for (int j = 0; j < 3; ++j) {
+            Coord ei, ej;
+            ei[i] = 1.0f;
+            ej[j] = 1.0f;
+            float expected = (i == j) ? 1.0f : 0.0f;
+            CHECK((poni_rot * (poni_rot_T * ej))[i] == Catch::Approx(expected).margin(1e-6));
+        }
+    }
+
+    // Test: S0 vector transformation
+    Coord S0 = geom.GetScatteringVector();
+    // For beam along z, S0 = (0, 0, 1/λ)
+    CHECK(S0.x == Catch::Approx(0.0f));
+    CHECK(S0.y == Catch::Approx(0.0f));
+    CHECK(S0.z == Catch::Approx(1.0f));
 }