Fix tests for julia versions 1.7 and lower

Author: Anton Reinhard

src/compton/differential_cross_section.jl

@@ -37,6 +37,21 @@ function _differential_cross_section(
         process, model, photon_in, electron_in, photon_out, electron_out
     )
 
+    # TODO: replace this with some less computationally intensive way to figure out how many states there are
+    photon_in_bstate = Vector{SLorentzVector{ComplexF64}}(
+        base_state(
+            Photon(), Incoming(), photon_in, _spin_or_pol(process, Photon(), Incoming())
+        ),
+    )
+    electron_in_bstate = Vector{BiSpinor}(
+        base_state(
+            Electron(),
+            Incoming(),
+            electron_in,
+            _spin_or_pol(process, Electron(), Incoming()),
+        ),
+    )
+
     # average over incoming polarizations/spins, but sum over outgoing pols/spins
     normalization = 1.0 / (length(photon_in_bstate) * length(electron_in_bstate))
     I = photon_in * electron_in

src/interfaces/process_interface.jl

@@ -118,12 +118,12 @@ function differential_cross_section(
 ) where {T<:QEDbase.AbstractFourMomentum}
     size(in_phasespace, 1) == number_incoming_particles(proc_def) || throw(
         DimensionMismatch(
-            "The number of momenta in the in-phasespace $(length(in_phasespace)) does not match the number of incoming particles of the process $(number_incoming_particles(proc_def)).",
+            "The number of momenta in the in-phasespace $(size(in_phasespace, 1)) does not match the number of incoming particles of the process $(number_incoming_particles(proc_def)).",
         ),
     )
     size(out_phasespace, 1) == number_outgoing_particles(proc_def) || throw(
         DimensionMismatch(
-            "The number of momenta in the out-phasespace $(length(out_phasespace)) does not match the number of outgoing particles of the process $(number_outgoing_particles(proc_def)).",
+            "The number of momenta in the out-phasespace $(size(out_phasespace, 1)) does not match the number of outgoing particles of the process $(number_outgoing_particles(proc_def)).",
         ),
     )
     return _differential_cross_section(proc_def, model_def, in_phasespace, out_phasespace)

test/compton.jl

@@ -48,11 +48,18 @@ end
             @test_throws DimensionMismatch differential_cross_section(
                 proc, model, invalid, valid
             )
-            @test_throws "incoming" differential_cross_section(proc, model, invalid, valid)
             @test_throws DimensionMismatch differential_cross_section(
                 proc, model, valid, invalid
             )
-            @test_throws "outgoing" differential_cross_section(proc, model, valid, invalid)
+            if VERSION >= v"1.8"
+                # this syntax is not supported in julia version 1.7 or below
+                @test_throws "incoming" differential_cross_section(
+                    proc, model, invalid, valid
+                )
+                @test_throws "outgoing" differential_cross_section(
+                    proc, model, valid, invalid
+                )
+            end
         end
     end