Add unit tests parallelization (Synthetixio#1272)

* Add --parallel flag to npm run test command

It can be used with 'npm run test -- --parallel'

* Add mocha override on hardhat test task

* Add parallelism for unit tests on ci config

* add --jobs flag to npm run tests command defaulted to 4

* update mocha tests timeout from 30secs to 60 secs

Author: mjlescano

.circleci/config.yml

@@ -248,6 +248,7 @@ jobs:
           username: $DOCKERHUB_USERNAME
           password: $DOCKERHUB_TOKEN
     resource_class: large
+    parallelism: 8
     steps:
       - checkout
       - attach_workspace:
@@ -257,7 +258,9 @@ jobs:
           name: Test and output gas used
           command: |
             set +e
-            npm test
+            circleci tests glob 'test/contracts/*.js' |
+            circleci tests split |
+            xargs npm test
             EXIT_CODE=$?
             cat test-gas-used.log
             printf "\\n"

.circleci/src/jobs/job-unit-tests.yml

@@ -1,6 +1,7 @@
 # Runs all unit and spec tests
 {{> job-header.yml}}
 resource_class: large
+parallelism: 8
 steps:
   - checkout
   - attach_workspace:
@@ -10,7 +11,9 @@ steps:
       name: Test and output gas used
       command: |
         set +e
-        npm test
+        circleci tests glob 'test/contracts/*.js' |
+        circleci tests split |
+        xargs npm test
         EXIT_CODE=$?
         cat test-gas-used.log
         printf "\\n"

hardhat.config.js

@@ -65,6 +65,6 @@ module.exports = {
 		outputFile: 'test-gas-used.log',
 	},
 	mocha: {
-		timeout: 30e3, // 30s
+		timeout: 60e3, // 60s
 	},
 };

hardhat/tasks/task-test.js

@@ -1,22 +1,45 @@
-const { task } = require('hardhat/config');
+const Mocha = require('mocha');
+const { types, task, subtask } = require('hardhat/config');
+const { TASK_TEST_RUN_MOCHA_TESTS } = require('hardhat/builtin-tasks/task-names');
 const { gray, yellow } = require('chalk');
 const optimizeIfRequired = require('../util/optimizeIfRequired');
 
+// Override builtin "test:run-mocha-tests" subtask so we can use the local mocha
+// installation, which is up to date and allows us to run parallel tests.
+subtask(TASK_TEST_RUN_MOCHA_TESTS).setAction(async ({ testFiles }, { config }) => {
+	const mocha = new Mocha(config.mocha);
+	testFiles.forEach(file => mocha.addFile(file));
+
+	const testFailures = await new Promise(resolve => {
+		mocha.run(resolve);
+	});
+
+	return testFailures;
+});
+
 task('test')
 	.addFlag('optimizer', 'Compile with the optimizer')
 	.addFlag('gas', 'Compile gas usage')
 	.addFlag('native', 'Compile with the native solc compiler')
+	.addFlag('parallel', 'Run tests in parallel')
+	.addOptionalParam('jobs', 'Max number of worker processes for parallel runs', 4, types.int)
 	.addOptionalParam('gasOutputFile', 'Gas reporter output file')
 	.addOptionalParam('grep', 'Filter tests to only those with given logic')
 	.setAction(async (taskArguments, hre, runSuper) => {
-		const { gas, grep, native, gasOutputFile } = taskArguments;
+		const { gas, grep, native, gasOutputFile, parallel, jobs } = taskArguments;
 
 		if (native) {
 			hre.config.solc.native = true;
 		}
 
 		optimizeIfRequired({ hre, taskArguments });
 
+		if (parallel) {
+			console.log(gray(`Running tests in parallel. Jobs count: ${jobs}`));
+			hre.config.mocha.parallel = true;
+			hre.config.mocha.jobs = jobs;
+		}
+
 		if (grep) {
 			console.log(gray('Filtering tests to those containing'), yellow(grep));
 			hre.config.mocha.grep = grep;