Add test coverage and integrate it to Codecov.

.circleci/config.yml

@@ -53,6 +53,14 @@ jobs:
           at: ~/
       - run: yarn test
 
+  coverage:
+    <<: *defaults
+    steps:
+      - attach_workspace:
+          at: ~/
+      - run: yarn test:coverage
+      - run:  yarn codecov
+
 workflows:
   version: 2
   build-and-test:
@@ -70,3 +78,6 @@ workflows:
       - test:
           requires:
             - install
+      - coverage:
+          requires:
+            - install

package.json

@@ -25,6 +25,7 @@
     "test:ts": "jest",
     "test:babel": "cross-env BABEL_TEST=1 jest",
     "test:dts": "tsc -p ./test-dts",
+    "test:coverage": "cross-env BABEL_TEST=1 jest --coverage",
     "docs:dev": "vitepress dev docs",
     "docs:build": "vitepress build docs",
     "docs:serve": "vitepress serve docs",
@@ -63,6 +64,7 @@
     "babel-jest": "^26.3.0",
     "babel-loader": "^8.1.0",
     "conventional-changelog-cli": "^2.1.0",
+    "codecov": "^3.8.1",
     "cross-env": "^7.0.3",
     "css-loader": "^4.2.1",
     "jest": "^26.4.2",