diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 43551fe..e3f74bc 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -27,16 +27,34 @@ jobs:
         os: [ubuntu-latest, windows-latest, macOS-latest]
     steps:
       - uses: actions/checkout@v4
+
 #     - name: "Set up Julia"
       - uses: julia-actions/setup-julia@latest
         with:
           version: ${{ matrix.version }}
+
+      - name: Cache artifacts
+        uses: actions/cache@v4
+        env:
+          cache-name: cache-artifacts
+        with:
+          path: ~/.julia/artifacts
+          key: ${{ runner.os }}-test-${{ env.cache-name }}-${{ hashFiles('**/Project.toml') }}
+          restore-keys: |
+            ${{ runner.os }}-test-${{ env.cache-name }}-
+            ${{ runner.os }}-test-
+            ${{ runner.os }}-
+
 #     - name: "Unit Test"
       - uses: julia-actions/julia-buildpkg@latest
       - uses: julia-actions/julia-runtest@latest
+
 #     - name: "Cover"
       - uses: julia-actions/julia-processcoverage@v1
       - uses: codecov/codecov-action@v5
         if: ${{ matrix.version == '1' && matrix.os == 'ubuntu-latest' }}
         with:
           file: lcov.info
+          fail_ci_if_error: false
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
diff --git a/src/backproject.jl b/src/backproject.jl
index c02613d..8052348 100644
--- a/src/backproject.jl
+++ b/src/backproject.jl
@@ -23,7 +23,7 @@ function backproject!(
                   plan.planrot[thid],
                   )
 
-    end
+    end # COV_EXCL_LINE
 
     # adjoint of convolving img with psf and applying attenuation map
     Threads.@threads for y in 1:plan.imgsize[2] # 1:ny
@@ -45,7 +45,7 @@ function backproject!(
                        )
 
         mul3dj!(plan.imgr, plan.exp_mumapr[thid], y)
-    end
+    end # COV_EXCL_LINE
 
     # adjoint of rotating image
     Threads.@threads for z in 1:plan.imgsize[3] # 1:nz
@@ -56,7 +56,7 @@ function backproject!(
                       plan.viewangle[viewidx],
                       plan.planrot[thid],
                       )
-    end
+    end # COV_EXCL_LINE
 
     return image
 end
@@ -142,7 +142,7 @@ function backproject!(
         Threads.@threads for (i, viewidx) in collect(enumerate(index))
             thid = Threads.threadid()
             backproject!(plan.add_img[thid], (@view views[:, :, i]), plan, thid, viewidx)
-        end
+        end # COV_EXCL_LINE
 
         for i in 1:plan.nthread
             broadcast!(+, image, image, plan.add_img[i])
diff --git a/src/project.jl b/src/project.jl
index 0a0bc31..97095fc 100644
--- a/src/project.jl
+++ b/src/project.jl
@@ -31,7 +31,7 @@ function project!(
             plan.viewangle[viewidx],
             plan.planrot[thid],
         )
-    end
+    end # COV_EXCL_LINE
 
     Threads.@threads for y in 1:plan.imgsize[2] # 1:ny
         thid = Threads.threadid() # thread id
@@ -55,7 +55,7 @@ function project!(
             (@view plan.psfs[:, :, y, viewidx]),
             plan.planpsf[thid],
         )
-    end
+    end # COV_EXCL_LINE
 
     copy3dj!(view, plan.add_img, 1) # initialize accumulator
     for y in 2:plan.imgsize[2] # accumulate to get total view
@@ -151,7 +151,7 @@ function project!(
         Threads.@threads for (i, viewidx) in collect(enumerate(index))
             thid = Threads.threadid()
             project!((@view views[:,:,i]), image, plan, thid, viewidx)
-        end
+        end # COV_EXCL_LINE
     else
         for (i, viewidx) in collect(enumerate(index))
             project!((@view views[:,:,i]), image, plan, viewidx)
diff --git a/src/rotatez.jl b/src/rotatez.jl
index 8ff5495..ee9aad1 100644
--- a/src/rotatez.jl
+++ b/src/rotatez.jl
@@ -520,7 +520,7 @@ function _imrotate!(
             θ,
             plans[id],
         )
-    end
+    end # COV_EXCL_LINE
 
     return output
 end