baseline

Baseline

This is a work in progress. Check back in a couple weeks.

Table of contents

• Installation
• Test suites
• Establishing a baseline
• Updating a baseline
• Comparison tests
• Asynchronous tests

## Installation

Baseline can be installed using npm:

$ npm install -g baseline

## Test suites

Test suites follow a paradigm similar to the mocha unit test framework. Suppose you have a file test.js:

suite("Regexp vs indexOf", function() {

    var str = "hello world!";
    var reg = /world/;

    test("Regexp", function() {
        reg.test(str);
    });

    test("indexOf", function() {
        str.indexOf("world");
    });
});

We then run Baseline, passing it the name of the file containing the test suite we want to execute:

$ baseline test.js

Regexp vs indexOf
  Regexp: 15,297,117 ops/sec ±1.27%
  indexOf: 21,860,061 ops/sec ±0.68%


Completed 2 tests.

Each test is executed repeatedly until a statistically significant result can be established. The result is reported in operations per second along with the relative margin of error. All statistical calculations are based on the Benchmark.js library.

## Establishing a baseline

Baseline can save the results of test runs to a file. Future runs of the same tests can then be compared against the saved results to determine if performance has changed. To establish a baseline, run Baseline with a the -b option, providing the name of the file to use.

$ baseline -b results.json test.js

## Comparing against a baseline

Once a baseline file has been created, if the program is run with the -b option again, the tests will be compared against the established baseline. If the change in the performance of a test compared to its baseline is at least 10%, the test is reported as changed.

$ baseline -b results.json test.js

Tests will be compared to baseline established on 2/24/2015 at 10:11:58 PM.

Regexp vs indexOf
  Regexp: 13,614,434 ops/sec ±0.73% (11% slower than baseline)
  indexOf: 21,564,642 ops/sec ±1.11%


Completed 2 tests, 1 slower.

The default threshold of 10% can be adjusted using the -T option. Below is an example of running Baseline with a threshold of 5%:

$ baseline -b results.json -T 5 test.js

## Updating a baseline

Executing tests with the -b option will not change the baseline file once it has been created. Use the -u option to update the baseline file with the result of the current test run.

$ baseline -b results.json -u test.js

## Comparison tests

Similar to jsperf.com, Baseline is able to compare the performance of several different tests and report, with statistical significance, which tests are fastest, which are slowest, and by how much. Use the compare function instead of suite to create a comparison test.

compare("Regexp vs indexOf", function() {

    var str = "hello world!";
    var reg = /world/;

    test("Regexp", function() {
        reg.test(str);
    });

    test("indexOf", function() {
        str.indexOf("world");
    });
});

Executing Baseline with this comparison test results in the following output:

$ baseline test.js

Regexp vs indexOf
  Regexp: 14,951,082 ops/sec ±1.67% (28% slower)
  indexOf: 20,680,257 ops/sec ±0.87% (fastest)


Completed 2 tests.

Note that comparison tests are never compared to a baseline, even if the -b option is specified.

## Asynchronous tests

Similar to mocha, asynchronous tests are accomplished by include a callback, usually called done, as a parameter to the test function. The callback must be called once the test has completed.

compare("process.nextTick vs setTimeout vs setImmediate", function() {

    test("process.nextTick", function(done) {
        process.nextTick(done);
    });

    test("setTimeout", function(done) {
        setTimeout(done, 0);
    });

    test("setImmediate", function(done) {
        setImmediate(done);
    });
});

Baseline will automatically determine if the test should be execute as a synchronous or asynchronous test based on the absence or presence of the callback in the test function. Also note that the callback accepts an Error object as a parameter.