For development of Test262-harness, test authoring & execution:

git clone https://github.com/tc39/test262.git --depth 1
cd test262

For test authoring & execution:

npm install -g test262-harness

Run test262-harness --help for details on the various configuration options.

Running tests in hypothetical JavaScript engine "X":

cd test262;
test262-harness --host-type=X --host-path=`which X` test/**/*.js

The --preprocessor feature allows a module that exports a map function that operates on each Test262Test object (ie. the object emitted by Test262-Stream) before their execution.

In some cases, a preprocessor may want to signal to Test262-Harness that a certain result has already been reached, and that it must not further evaluate the test. To create this signal, the preprocessor creates a result property on the Test262Test object, which will indicate to Test262-Harness that it must not evaluate the test, but instead return the value of the result property as though the test had been executed. For example, a preprocessor may attempt to transpile the value of test.contents—which may fail! In the case of failure, the preprocessor can create a result property whose value is a Result Object. This will skip the code evaluation and report the given result object.

module.exports = function(test) {
  try {
    test.contents = babel.transform(test.contents, options).code;
  } catch (error) {
    test.result = {
      stderr: `${error.name}: ${error.message}\n`,
      stdout: '',
      error
    };
  }

  return test;
};