chore: Fix coverage test (#14802)

* chore: Improve test-cov

* rebase

CONTRIBUTING.md

@@ -210,8 +210,7 @@ $ OVERWRITE=true TEST_ONLY=babel-plugin-transform-classes make test-only
 To test the code coverage, use:
 
 ```sh
-$ BABEL_ENV=cov make build
-$ ./scripts/test-cov.sh
+make test-cov
 ```
 
 #### Troubleshooting Tests

Makefile

@@ -81,6 +81,9 @@ fix-json:
 clean:
 	$(MAKEJS) clean
 
+test-cov:
+	$(MAKEJS) test-cov
+
 test: lint test-only
 
 clone-license:
@@ -137,14 +140,12 @@ update-env-corejs-fixture:
 	OVERWRITE=true $(YARN) jest packages/babel-preset-env
 
 test-ci: build-standalone-ci
-	BABEL_ENV=test $(YARN) jest --maxWorkers=4 --ci
+	BABEL_ENV=test $(YARN) jest --maxWorkers=100% --ci
 	$(MAKE) test-clean
 
-# Does not work on Windows
-test-ci-coverage: SHELL:=/bin/bash
 test-ci-coverage:
-	BABEL_COVERAGE=true BABEL_ENV=test $(MAKE) bootstrap
-	BABEL_ENV=test TEST_TYPE=cov ./scripts/test-cov.sh
+	BABEL_ENV=test BABEL_COVERAGE=true $(MAKE) bootstrap
+	BABEL_ENV=test BABEL_COVERAGE=true $(YARN) jest --maxWorkers=100% --ci
 
 bootstrap-flow:
 	rm -rf build/flow

Makefile.source.mjs

@@ -377,6 +377,19 @@ target["test-only"] = function (args = []) {
   yarn(["jest", ...args]);
 };
 
+target["test-cov"] = function () {
+  env(
+    () => {
+      target["build"]();
+      yarn(["jest", "--coverage"]);
+    },
+    {
+      BABEL_ENV: "test",
+      BABEL_COVERAGE: "true",
+    }
+  );
+};
+
 /**
  * PUBLISH
  */

jest.config.js

@@ -37,7 +37,7 @@ module.exports = {
     // in production builds. They are marked using the .skip-bundled.js extension.
     ...(isPublishBundle ? ["\\.skip-bundled\\.js$"] : []),
     // Ignore @babel/standalone test in coverage testing because it is not built
-    ...(process.env.TEST_TYPE === "cov"
+    ...(process.env.BABEL_COVERAGE === "true"
       ? ["<rootDir>/packages/babel-standalone/"]
       : []),
   ],

scripts/test.sh

@@ -10,7 +10,7 @@ if [ "$TEST_DEBUG" ]; then
 fi
 
 if [ -n "$CI" ]; then
-  jestArgs+=("--maxWorkers=4")
+  jestArgs+=("--maxWorkers=100%")
   jestArgs+=("--ci")
 fi