test: migrate test.js to support concurrent test execution (#1531)

This patch migrates tests so that they can be run concurrently.

- By default, tests still run in one thread.
- To run tests in 4 parallel threads, run node test/test.js -j 4 or npm run unit -- -j 4
- Environment variable PPTR_PARALLEL_TESTS could be set to override default parallelization

Every test gets passed in a state. State is set up in the beforeAll and beforeEach callbacks,
and should be teared down in the afterAll and afterEach callbacks.

By default, state has a parallelIndex variable initialized that defines the thread index that runs the execution.

utils/testrunner/README.md

@@ -1,6 +1,6 @@
 # TestRunner
 
-- no additional binary required; tests are `node.js` scripts
+- testrunner is a library: no additional binary required; tests are `node.js` scripts
 - parallel wrt IO operations
 - supports async/await
 - modular
@@ -25,7 +25,7 @@ const {it, fit, xit} = runner;
 const {beforeAll, beforeEach, afterAll, afterEach} = runner;
 
 beforeAll(state => {
-  state.parallel; // this will be set with the execution thread id, either 0 or 1 in this example
+  state.parallelIndex; // either 0 or 1 in this example, depending on the executing thread
   state.foo = 'bar'; // set state for every test
 });
 

utils/testrunner/TestRunner.js

@@ -162,7 +162,7 @@ class TestPass {
 
     const workerPromises = [];
     for (let i = 0; i < this._parallel; ++i)
-      workerPromises.push(this._runSuite(i, [this._rootSuite], {parallel: i}));
+      workerPromises.push(this._runSuite(i, [this._rootSuite], {parallelIndex: i}));
     await Promise.all(workerPromises);
 
     for (const termination of terminations)