diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cb93ff8..a4559c7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,5 +38,5 @@ jobs:
         if: ${{ matrix.version == '1' && matrix.os == 'ubuntu-latest' }}
         with:
           file: lcov.info
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+          token: ${{ secrets.CODECOV_TOKEN }}
+          fail_ci_if_error: false
diff --git a/test/runtests.jl b/test/runtests.jl
index 8f7cb64..c5f9473 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,7 +1,15 @@
 # runtests.jl
 
 using Sinograms
-using Test: @test, @testset, detect_ambiguities
+using Test: @test, @test_throws, @testset, detect_ambiguities
+
+# test extension stubs before loading the extension
+@testset "exts" begin
+    @test_throws String sino_plot_rays()
+#   @test_throws String sino_geom_plot!()
+    @test_throws String ct_geom_plot2!()
+    @test_throws String ct_geom_plot3() # todo
+end
 
 include("units.jl")