Add code coverage reports

.gitignore

@@ -1,7 +1,9 @@
 *.egg-info
 *.pyc
+.coverage*
 .idea/
 .tox/
 .venv/
 build/
 dist/
+htmlcov/

tox.ini

@@ -2,7 +2,9 @@
 ; On Windows, only CPython >= 3.8 is supported.
 ; All older versions, and PyPy, lack full symlink support.
 envlist =
+    coverage_erase
     py{38, 39, 310}-all_platforms
+    coverage_report
     py{27, 35, 36, 37}-most_platforms
     pypy{2, 3}-most_platforms
     py39-black
@@ -20,9 +22,30 @@ deps =
     pytest-randomly
     pyyaml
     mock; python_version == "2.7"
+    all_platforms: coverage
 
 commands =
-    pytest tests/
+    all_platforms: coverage run -m pytest
+    most_platforms: pytest tests/
+
+
+[testenv:coverage_erase]
+skipsdist = true
+skip_install = true
+deps = coverage
+commands = coverage erase
+
+
+[testenv:coverage_report]
+skipsdist = true
+skip_install = true
+deps = coverage
+commands_pre =
+    coverage combine
+
+commands =
+    coverage report
+    coverage html
 
 
 [testenv:py39-black]
@@ -43,3 +66,15 @@ deps =
 
 commands =
     isort --check dotbot/ tests/
+
+
+[coverage:run]
+branch = true
+parallel = true
+source =
+    dotbot/
+    tests/
+
+
+[coverage:html]
+directory = htmlcov