Disable collecting test coverage by default (#2456)

Co-authored-by: Valeriu Predoi <[email protected]>

.circleci/config.yml

@@ -21,14 +21,18 @@ commands:
               circleci step halt
             fi
   test_and_report:
+    parameters:
+      args:
+        type: string
+        default: ""
     steps:
       - run:
           name: Run tests
           command: |
             mkdir -p test-reports
             . /opt/conda/etc/profile.d/conda.sh
             conda activate esmvaltool
-            pytest -n 4 --junitxml=test-reports/report.xml
+            pytest -n 4 --junitxml=test-reports/report.xml << parameters.args >>
             esmvaltool version
       - store_test_results:
           path: test-reports/report.xml
@@ -127,8 +131,9 @@ jobs:
             . /opt/conda/etc/profile.d/conda.sh
             mkdir /logs
             conda activate esmvaltool
-            pip install .[test] |& tee -a /logs/install.txt
-      - test_and_report
+            pip install .[test] > /logs/install.txt 2>&1
+      - test_and_report:
+          args: --cov
       - save_cache:
           key: test-{{ .Branch }}-{{ checksum "cache_key.txt" }}
           paths:

doc/contributing.rst

@@ -470,9 +470,16 @@ successful.
 Test coverage
 ~~~~~~~~~~~~~
 
-To check which parts of your code are `covered by unit tests`_, open the file
-``test-reports/coverage_html/index.html`` (available after running a ``pytest``
-command) and browse to the relevant file.
+To check which parts of your code are `covered by unit tests`_, run the command
+
+.. code-block:: bash
+
+   pytest --cov
+
+and open the file ``test-reports/coverage_html/index.html`` and browse to the
+relevant file. Note that tracking code coverage slows down the test runs,
+therefore it is disabled by default and needs to be requested by providing
+``pytest`` with the ``--cov`` flag.
 
 CircleCI will upload the coverage results from running the tests to codecov and
 Codacy.

setup.cfg

@@ -2,7 +2,6 @@
 addopts =
     --doctest-modules
     --ignore=esmvalcore/cmor/tables/
-    --cov=esmvalcore
     --cov-report=xml:test-reports/coverage.xml
     --cov-report=html:test-reports/coverage_html
     --html=test-reports/report.html
@@ -15,6 +14,7 @@ markers =
 
 [coverage:run]
 parallel = true
+source = esmvalcore
 [coverage:report]
 exclude_lines =
     pragma: no cover