diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index f8a3b3e..59bb587 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -37,11 +37,6 @@ jobs:
         with:
           path: ~/.data/
           key: resources
-      - name: Set up Java
-        uses: actions/setup-java@v2
-        with:
-          distribution: "temurin" # See 'Supported distributions' for available options
-          java-version: "8"
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
@@ -59,14 +54,102 @@ jobs:
         if: matrix.python-version != '3.9'
 
       - name: Test with Pytest on Python ${{ matrix.python-version }}
+        run: coverage run -m pytest
+
+      - name: Upload coverage data
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-data-${{ matrix.python-version }}
+          path: .coverage.*
+          if-no-files-found: ignore
+
+  Coverage:
+    name: Combine & check coverage
+    if: always()
+    needs: Pytest
+    runs-on: ubuntu-latest
+    env:
+      GITHUB_PR_NUMBER: ${{github.event.pull_request.number}}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          # Use latest Python, so it understands all syntax.
+          python-version: "3.7"
+
+      - uses: actions/download-artifact@v4
+        with:
+          pattern: coverage-data-*
+          merge-multiple: true
+
+      - name: Combine coverage and generate report
+        run: |
+          python -Im pip install --upgrade "git+https://github.com/percevalw/coveragepy.git#egg=coverage[toml]"
+
+          ls -lah
+
+          python -Im coverage combine
+
+          # Report and write to summary.
+          python -Im coverage report --skip-covered --skip-empty --format=detailed-markdown >> $GITHUB_STEP_SUMMARY
+          echo '## Coverage Report' > step-summary.md
+          cat $GITHUB_STEP_SUMMARY >> step-summary.md
+
+          coverage report > coverage-report.txt
+          echo "main_coverage=$(grep 'TOTAL' coverage-report.txt | awk '{print $NF}' | sed 's/%//')" > main-coverage.txt
+
+      - name: Upload Coverage Percentage for Main
+        uses: actions/upload-artifact@v4
+        if: github.ref == 'refs/heads/main' || github.ref == 'refs/heads/main'
+        with:
+          name: main-coverage-percentage
+          path: main-coverage.txt
+
+      - name: Compare Coverage Percentages
+        if: github.ref != 'refs/heads/main' && github.ref != 'refs/heads/main' && github.event_name == 'pull_request'
         env:
-          UMLS_API_KEY: ${{ secrets.UMLS_API_KEY }}
-        run: python -m pytest --cov foldedtensor --cov-report xml
-        if: matrix.python-version == '3.9'
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+
+          main_coverage=$(cat ./.github/workflows/artifacts/main-coverage.txt || echo "90")
+          branch_coverage=$(coverage report | grep 'TOTAL' | awk '{print $NF}' | sed 's/%//')
+
+          # echo "Main Coverage: $main_coverage%" > step-summary.md
+          # echo "Branch Coverage: $branch_coverage%" > step-summary.md
+
+          # Echo comparison in with cross if it's lower, and checkmark if it's higher.
+          if (( $(echo "$branch_coverage < $main_coverage" | bc -l) )); then
+            echo "Coverage has decreased from the main branch."
+            echo >> step-summary.md
+            echo "Branch Coverage: $branch_coverage% < Main Coverage: $main_coverage% :x:" >> step-summary.md
+            FAILED=true
+          else
+            echo "Coverage is sufficient or improved."
+            echo >> step-summary.md
+            echo "Branch Coverage: **$branch_coverage%** ≥ Main Coverage: **$main_coverage%** :white_check_mark:" >> step-summary.md
+            FAILED=false
+          fi
+
+          COMMENT_BODY_JSON=$(jq -Rs . <<< $(cat step-summary.md))
+          HEADER="Authorization: token $GITHUB_TOKEN"
+          PR_COMMENTS_URL="https://api.github.com/repos/${{ github.repository }}/issues/${{ github.event.pull_request.number }}/comments"
+
+          # Fetch existing comments to find if one from this workflow already exists
+          COMMENTS=$(curl -s -H "$HEADER" "$PR_COMMENTS_URL")
+          COMMENT_ID=$(echo "$COMMENTS" | jq -r '.[] | select(.user.login == "github-actions[bot]" and (.body | startswith("## Coverage Report"))) | .id')
+
+          # Check if we have a comment ID, if so, update it, otherwise create a new one
+          if [[ "$COMMENT_ID" ]]; then
+            # Update existing comment
+            curl -s -X PATCH -H "$HEADER" -H "Content-Type: application/json" -d "{\"body\": $COMMENT_BODY_JSON}" "https://api.github.com/repos/${{ github.repository }}/issues/comments/$COMMENT_ID"
+          else
+            # Post new comment
+            curl -s -X POST -H "$HEADER" -H "Content-Type: application/json" -d "{\"body\": $COMMENT_BODY_JSON}" "$PR_COMMENTS_URL"
+          fi
 
-      - name: Upload coverage
-        uses: codecov/codecov-action@v2
-        if: matrix.python-version == '3.9'
+          if [[ "$FAILED" == "true" ]]; then
+              exit 1
+          fi
 
   Installation:
     runs-on: ubuntu-latest
diff --git a/pyproject.toml b/pyproject.toml
index 51ae8ee..08a0c14 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -54,6 +54,14 @@ testpaths = [
     "tests",
 ]
 
+[tool.coverage.run]
+concurrency = ["multiprocessing"]
+parallel = true
+include = ['foldedtensor/*']
+
+[tool.coverage.report]
+include = ['foldedtensor/*']
+precision = 1
 
 [build-system]
 requires = [