diff --git a/.coveragerc b/.coveragerc
new file mode 100644
index 0000000..62c8418
--- /dev/null
+++ b/.coveragerc
@@ -0,0 +1,6 @@
+[run]
+branch = true
+source =
+    kosmorrolib
+omit =
+    tests/*
diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
index 4fc38e4..424be74 100644
--- a/.github/workflows/unit-tests.yml
+++ b/.github/workflows/unit-tests.yml
@@ -35,12 +35,8 @@ jobs:
         pipenv lock --pre
         pipenv sync --dev
     - name: Unit tests
-      env:
-        COVERALLS_PRO_TOKEN: ${{ secrets.COVERALLS_TOKEN }}
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: |
-        make test
-        pipenv run coveralls --service=github
+        make legacy-tests
 
   unit-tests:
     runs-on: ${{ matrix.os }}
@@ -74,5 +70,5 @@ jobs:
         COVERALLS_PRO_TOKEN: ${{ secrets.COVERALLS_TOKEN }}
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: |
-        make test
+        make doctests
         pipenv run coveralls --service=github
diff --git a/Makefile b/Makefile
index 8654a81..dfc4112 100644
--- a/Makefile
+++ b/Makefile
@@ -2,14 +2,16 @@ black:
 	pipenv run black kosmorrolib tests
 
 .PHONY: test
-tests: legacy-tests
-	python3 tests.py
+tests: legacy-tests doctests
+
+doctests:
+	pipenv run python3 -m coverage run tests.py
 
 legacy-tests:
 	unset KOSMORRO_LATITUDE; \
 	unset KOSMORRO_LONGITUDE; \
 	unset KOSMORRO_TIMEZONE; \
-	LANG=C pipenv run python3 -m coverage run -m unittest tests
+	pipenv run python3 -m coverage run -m unittest tests
 
 .PHONY: build
 build: