diff --git a/.github/workflows/dev-test.yml b/.github/workflows/dev-test.yml
index c7fd7e5..6eecfbd 100644
--- a/.github/workflows/dev-test.yml
+++ b/.github/workflows/dev-test.yml
@@ -36,13 +36,13 @@ jobs:
 
       - name: Test with pytest
         run: |
-          python -m pytest -vv --cov=. --cov-report=xml
+          python -m pytest -vv --cov=. --cov-report=json
 
       - name: Upload coverage report
         uses: actions/upload-artifact@v4
         with:
           name: coverage-${{ matrix.os }}-${{ matrix.python-version }}
-          path: coverage.xml
+          path: coverage.json
 
   coverage:
     needs: tests
@@ -55,11 +55,5 @@ jobs:
         with:
           path: coverage-reports
 
-      - name: Install lcov 
-        run:  sudo apt-get install lcov
-
-      - name: Merge coverage reports
-        run: 'lcov $(find coverage-reports -name "*xml" | while read -r F ; do echo -a $F ; done) -o coverage-merged.info'
-
       - name: Check coverage
-        run: lcov --summary coverage-merged.info
+        run: python3 check_coverage_reports.py --inp-dir coverage-reports --max-allowed-num-uncovered-lines 0
diff --git a/tests/test_core.py b/tests/test_core.py
index dd1ce80..d5ec577 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -17,6 +17,31 @@ def check_(**kwargs):
     return check_
 
 
+def test_replace():
+    fmt = Format(
+        max_value_str_len=1,
+        objects_details=1,
+        ellipsis_rel_pos=0.5,
+        max_exc_str_len=1,
+        ellipsis_='.',
+        before=1,
+        after=1,
+        color_scheme=None,
+        skip_files_except=[],
+        brief_files_except=[],
+        custom_var_printers=[],
+    )
+    fmt2 = fmt.replace(
+        before=2,
+        skip_files_except=['f1', 'f2'],
+    )
+    assert fmt.max_value_str_len == fmt.max_value_str_len
+    assert fmt2.before == 2
+    assert fmt.before == 1
+    assert fmt2.skip_files_except == ['f1', 'f2']
+    assert fmt.skip_files_except == []
+
+
 def test_setattr():
     fmt = Format()
     fmt.max_value_str_len = 1