diff --git a/.github/workflows/run-tests-push.yml b/.github/workflows/run-tests-push.yml
index 35e5b23..0c5cc71 100644
--- a/.github/workflows/run-tests-push.yml
+++ b/.github/workflows/run-tests-push.yml
@@ -17,7 +17,7 @@ jobs:
 #    - run: xvfb-run pytest tests/
     - run: tests/cmd_tests.sh
 
-  run-tests-ubuntu-22_04-python-3_10:
+  run-tests-ubuntu-22_04-python-3_10-with-coverage:
     runs-on: ubuntu-22.04
     name: Ubuntu 22.04, Python 3.10
     steps:
@@ -28,8 +28,13 @@ jobs:
     - run: sudo apt install xvfb
     - run: pip install --upgrade pip
     - run: pip install .[dev]
-    - run: xvfb-run pytest tests/
+    - run: xvfb-run coverage run --source countess -m pytest tests/
+    - run: coverage html
     - run: tests/cmd_tests.sh
+    - uses: actions/upload-artifact@v3
+      with:
+        name: test coverage report
+        path: htmlcov/index.html
 
 #  run-tests-ubuntu-22_04-python-3_11_0rc2:
 #   runs-on: ubuntu-22.04
diff --git a/pyproject.toml b/pyproject.toml
index b4500e6..72fb42b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -33,6 +33,7 @@ dependencies = [
 dev = [
     'black<24',
     'build==0.10.0',
+    'coverage==7.3.2',
     'mypy~=1.0.1',
     'pylint~=2.17',
     'types-psutil~=5.9.5',
diff --git a/tests/utils/test_pandas.py b/tests/utils/test_pandas.py
new file mode 100644
index 0000000..38f596d
--- /dev/null
+++ b/tests/utils/test_pandas.py
@@ -0,0 +1,39 @@
+import pytest
+
+import pandas as pd
+
+from countess.utils.pandas import *
+
+df0 = pd.DataFrame([])
+df1 = pd.DataFrame([ {'a': n, 'b': n*100 } for n in range(0,100) ]).set_index('a')
+df2 = pd.DataFrame([ {'a': n, 'b': n*100 } for n in range(100,1000) ]).set_index('a')
+df3 = pd.DataFrame([ {'a': n, 'b': n*100 } for n in range(1000,10000) ]).set_index('a')
+df4 = pd.DataFrame([ {'a': n, 'b': n*100 } for n in range(10000,10100) ]).set_index('a')
+df5 = pd.DataFrame([ {'a': n, 'b': n*100 } for n in range(10100,10200) ]).set_index('a')
+df6 = pd.DataFrame([ {'a': n, 'b': n*100 } for n in range(10200,10300) ]).set_index('a')
+
+def assert_iterable_of_dataframes_equal(a,b):
+
+    assert pd.concat(a).sort_index().equals(
+        pd.concat(b).sort_index()
+    )
+
+def test_collect_dataframes_0():
+
+    x = list(collect_dataframes([df0,df0,None,df0].__iter__()))
+    assert len(x) == 0
+
+def test_collect_dataframes_1():
+    x = list(collect_dataframes([df1,df4,df5].__iter__(), 300))
+    assert_iterable_of_dataframes_equal([df1,df4,df5], x)
+    assert min(len(y) for y in x) > 100
+
+def test_collect_dataframes_2():
+    x = list(collect_dataframes([df1,df2,df4,df5].__iter__(), 300))
+    assert_iterable_of_dataframes_equal([df1,df2,df4,df5], x)
+    assert min(len(y) for y in x) > 100
+
+def test_collect_dataframes_3():
+    x = list(collect_dataframes([df1,df2,df4,df5,df6].__iter__(), 300))
+    assert_iterable_of_dataframes_equal([df1,df2,df4,df5,df6], x)
+    assert len(x) < 5