diff --git a/pineappl/src/empty_subgrid.rs b/pineappl/src/empty_subgrid.rs
index 5f2acfea..4977d082 100644
--- a/pineappl/src/empty_subgrid.rs
+++ b/pineappl/src/empty_subgrid.rs
@@ -55,6 +55,8 @@ impl Subgrid for EmptySubgridV1 {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::packed_array::PackedArray;
+    use crate::packed_subgrid::PackedQ1X2SubgridV1;
     use crate::v0;
 
     #[test]
@@ -84,6 +86,21 @@ mod tests {
         subgrid.fill(&v0::default_interps(2), &[0.0; 3], 0.0);
     }
 
+    #[test]
+    #[should_panic(
+        expected = "EmptySubgridV1 doesn't support the merge operation for non-empty subgrids"
+    )]
+    fn merge_non_empty() {
+        let mut subgrid_lhs = EmptySubgridV1;
+
+        let mut array = PackedArray::new(vec![1, 1]);
+        array[0] = 1.0;
+        let node_values = vec![NodeValues::UseThese(vec![1.0]); 2];
+        let subgrid_rhs = PackedQ1X2SubgridV1::new(array, node_values).into();
+
+        subgrid_lhs.merge(&subgrid_rhs, None);
+    }
+
     #[test]
     fn node_values() {
         assert!(EmptySubgridV1.node_values().is_empty());
diff --git a/pineappl/src/fk_table.rs b/pineappl/src/fk_table.rs
index f5ec3e76..5c3e117b 100644
--- a/pineappl/src/fk_table.rs
+++ b/pineappl/src/fk_table.rs
@@ -211,12 +211,12 @@ impl FkTable {
     /// Returns the single `muf2` scale of this `FkTable`.
     #[must_use]
     pub fn muf2(&self) -> f64 {
-        if let &[muf2] = &self.grid.evolve_info(&[true]).fac1[..] {
-            muf2
-        } else {
-            // every `FkTable` has only a single factorization scale
-            unreachable!()
-        }
+        let [muf2] = self.grid.evolve_info(&[true]).fac1[..]
+            .try_into()
+            // UNWRAP: every `FkTable` has only a single factorization scale
+            .unwrap_or_else(|_| unreachable!());
+
+        muf2
     }
 
     /// Returns the x grid that all subgrids for all hadronic initial states share.
diff --git a/pineappl/src/grid.rs b/pineappl/src/grid.rs
index 02dac604..19ddcb06 100644
--- a/pineappl/src/grid.rs
+++ b/pineappl/src/grid.rs
@@ -166,7 +166,9 @@ impl Grid {
         assert_eq!(
             interps.len(),
             kinematics.len(),
-            "interps and kinematics have different lengths"
+            "interps and kinematics have different lengths: {} vs. {}",
+            interps.len(),
+            kinematics.len(),
         );
 
         assert!(
@@ -1618,7 +1620,7 @@ mod tests {
 
     #[test]
     #[should_panic(expected = "channel #0 has wrong number of PIDs: expected 2, found 3")]
-    fn grid_new_panic() {
+    fn grid_new_panic0() {
         let channel = vec![(vec![1, -1, 1], 1.0), (vec![2, -2, 2], 1.0)];
 
         let _ = Grid::new(
@@ -1640,6 +1642,64 @@ mod tests {
         );
     }
 
+    #[test]
+    #[should_panic(expected = "interps and kinematics have different lengths: 2 vs. 3")]
+    fn grid_new_panic1() {
+        let channel = vec![(vec![1, -1], 1.0), (vec![2, -2], 1.0)];
+
+        let _ = Grid::new(
+            PidBasis::Pdg,
+            vec![Channel::new(channel)],
+            vec![Order::new(0, 2, 0, 0, 0)],
+            vec![0.0, 1.0],
+            vec![
+                Conv::new(ConvType::UnpolPDF, 2212),
+                Conv::new(ConvType::UnpolPDF, 2212),
+            ],
+            v0::default_interps(1),
+            vec![Kinematics::Scale(0), Kinematics::X1, Kinematics::X2],
+            Scales {
+                ren: ScaleFuncForm::Scale(0),
+                fac: ScaleFuncForm::Scale(0),
+                frg: ScaleFuncForm::NoScale,
+            },
+        );
+    }
+
+    #[test]
+    #[should_panic(expected = "scales and kinematics are not compatible")]
+    fn grid_new_panic2() {
+        let channel = vec![(vec![1, -1], 1.0), (vec![2, -2], 1.0)];
+
+        let _ = Grid::new(
+            PidBasis::Pdg,
+            vec![Channel::new(channel)],
+            vec![Order::new(0, 2, 0, 0, 0)],
+            vec![0.0, 1.0],
+            vec![
+                Conv::new(ConvType::UnpolPDF, 2212),
+                Conv::new(ConvType::UnpolPDF, 2212),
+            ],
+            v0::default_interps(2),
+            vec![Kinematics::Scale(0), Kinematics::X1, Kinematics::X2],
+            Scales {
+                ren: ScaleFuncForm::Scale(0),
+                fac: ScaleFuncForm::Scale(1),
+                frg: ScaleFuncForm::NoScale,
+            },
+        );
+    }
+
+    #[test]
+    fn grid_read_file_version_unsupported() {
+        assert!(matches!(
+            Grid::read(
+                &[b'P', b'i', b'n', b'e', b'A', b'P', b'P', b'L', 99, 0, 0, 0, 0, 0, 0, 0][..]
+            ),
+            Err(GridError::FileVersionUnsupported { file_version: 99 })
+        ));
+    }
+
     #[test]
     fn grid_merge_empty_subgrids() {
         let mut grid = Grid::new(
@@ -1898,6 +1958,35 @@ mod tests {
         );
     }
 
+    #[test]
+    fn grid_set_remapper_bin_number_mismatch() {
+        let mut grid = Grid::new(
+            PidBasis::Pdg,
+            vec![
+                channel![2, 2, 1.0; 4, 4, 1.0],
+                channel![1, 1, 1.0; 3, 3, 1.0],
+            ],
+            vec![Order::new(0, 2, 0, 0, 0)],
+            vec![0.0, 0.25, 0.5, 0.75, 1.0],
+            vec![Conv::new(ConvType::UnpolPDF, 2212); 2],
+            v0::default_interps(2),
+            vec![Kinematics::Scale(0), Kinematics::X1, Kinematics::X2],
+            Scales {
+                ren: ScaleFuncForm::Scale(0),
+                fac: ScaleFuncForm::Scale(0),
+                frg: ScaleFuncForm::NoScale,
+            },
+        );
+
+        assert!(matches!(
+            grid.set_remapper(BinRemapper::new(vec![1.0], vec![(0.0, 1.0)]).unwrap()),
+            Err(GridError::BinNumberMismatch {
+                grid_bins: 4,
+                remapper_bins: 1
+            })
+        ));
+    }
+
     #[test]
     fn evolve_info() {
         let grid =
diff --git a/pineappl_cli/tests/evolve.rs b/pineappl_cli/tests/evolve.rs
index 7e862ada..4f50125c 100644
--- a/pineappl_cli/tests/evolve.rs
+++ b/pineappl_cli/tests/evolve.rs
@@ -171,7 +171,7 @@ const NUTEV_CC_NU_FE_SIGMARED_STR: &str = "b     Grid       FkTable     rel. dif
 
 const CMS_TTB_8TEV_2D_TTM_TRAP_TOT_STR: &str = "b    Grid       FkTable     rel. diff
 -+-----------+-----------+-------------
-0 2.1596192e2 2.1590144e2 -2.8005486e-4
+0 2.0680644e2 2.0666857e2 -6.6663644e-4
 ";
 
 const STAR_WMWP_510GEV_WM_AL_POL: &str = "b    Grid       FkTable     rel. diff
@@ -406,6 +406,7 @@ fn cms_ttb_8tev_2d_ttm_trap_tot() {
         .args([
             "evolve",
             "--orders=as2,as3,as4",
+            "--xir=2",
             "../test-data/CMS_TTB_8TEV_2D_TTM_TRAP_TOT-opt.pineappl.lz4",
             "../test-data/CMS_TTB_8TEV_2D_TTM_TRAP_TOT.tar",
             output.path().to_str().unwrap(),