tape

This guide covers the ins-and-outs of tape, a simple TAP-producing test library for node and browsers.

For an exaustive list of all the methods that tape supports, consult the tape readme.

The tape API is a small superset of the node core assert module.

simple equality with a plan

Most of the time, you'll just need to plan out a few simple asserts with t.equal(), which uses === internally:

var test = require('tape');

test('basic arithmetic', function (t) {
    t.plan(2);

    t.equal(2 + 3, 5);
    t.equal(7 * 8 + 9, 65);
});

If you want you can leave off the test name and just do:

var test = require('tape');

test(function (t) {
    t.plan(2);

    t.equal(2 + 3, 5);
    t.equal(7 * 8 + 9, 65);
});

simple equality with an end

If you have an indefinite number of assertions, sometimes it's easier to call t.end() instead:

var test = require('tape');

test('basic arithmetic', function (t) {
    t.equal(2 + 3, 5);
    t.equal(7 * 8 + 9, 65);

    t.end();
});

deep equality

To compare array and object references deeply, you can use t.deepEqual():

var test = require('tape');

test('deep equality', function (t) {
    t.plan(2);

    t.deepEqual([ 3, 4, 5 ], [ 3, 4, 2+3 ]);
    t.deepEqual(
        { a: 7, b: [ 8, 9 ] },
        { a : 3+4, b: [ 4*2 ].concat(3*3) }
    );
});

comparing booleans

Just use .ok() to assert truthiness:

var test = require('tape');

test('comparing booleans', function (t) {
    t.plan(1);

    t.ok(3 > 4 || 5 > 2);
});

negations

For each kind of assertion, prepend (and camel-case) a not to turn it into a negative assertion:

var test = require('tape');

test('negatives', function (t) {
    t.plan(3);
    t.notEqual(1+2, 5);
    t.notDeepEqual([1,2], [12]);
    t.notOk(false);
});

pass/fail

If you need a test to just fail, you can call t.fail():

var test = require('tape');

test('empty map', function (t) {
    [].map(function (x) {
        t.fail('this callback should never fire');
    });

    t.end();
});

Conversely, there is a t.pass() which always succeeds:

var test = require('tape');

test('map with elements', function (t) {
    t.plan(2);

    [2,3].map(function (x) {
        t.pass();
    });
});

more info

You can always add an assertion description as the last argument:

var test = require('tape');

test('more info', function (t) {
    t.plan(2);

    t.equal(1+2, 3, 'basic arithmetic still works');
    t.ok(3+4>5, 'inequalities are as we might expect');
});

asynchronous

Since we either plan out the number of assertions explicitly with t.plan(n) or end the test explicitly with t.end(), we don't need to do anything differently when our tests make asynchronous calls:

var test = require('tape');

test('asynchronous results', function (t) {
    t.plan(2);

    t.equal(2+3, 5);

    setTimeout(function () {
        t.equal(5+5, 10);
    }, 500);
});

multiple serial tests

var test = require('tape');

test('first', function (t) {
    t.plan(1);
    setTimeout(function () { t.ok(true) }, 200);
});

test('second', function (t) {
    t.plan(1);
    setTimeout(function () { t.ok(true) }, 100);
});

The 'first' test will run, then the 'second'.

nesting tests

You probably shouldn't do this very often, but you can have nested tests too:

var test = require('tape');

test('nested', function (t) {
    t.test(function (st) {
        st.plan(1);
        st.equal(1+2, 3);
    });

    t.test(function (st) {
        st.plan(1);
        setTimeout(function () {
            st.pass();
        }, 100);
    });
});

running a tape test in node

Just run your test file directly with node:

$ node test/def.js 
TAP version 13
# defined-or
ok 1 empty arguments
ok 2 1 undefined
ok 3 2 undefined
ok 4 4 undefineds
ok 5 false[0]
ok 6 false[1]
ok 7 zero[0]
ok 8 zero[1]
ok 9 first arg
ok 10 second arg
ok 11 third arg

1..11
# tests 11
# pass  11

# ok

running a directory full of tape tests in node

If you npm install -g tape, you get a test runner for running directories full of tests all at once:

$ tape test/*.js
TAP version 13
# defined-or
ok 1 empty arguments
ok 2 1 undefined
ok 3 2 undefined
ok 4 4 undefineds
ok 5 false[0]
ok 6 false[1]
ok 7 zero[0]
ok 8 zero[1]
ok 9 first arg
ok 10 second arg
ok 11 third arg
# (anonymous)
ok 12 should be equal

1..12
# tests 12
# pass  12

# ok

You could also use the test runner from the tap module for more terse output. npm install -g tap, then do:

$ tap test/*.js
ok test/def.js ........................................ 12/12
ok test/falsy.js ........................................ 2/2
total ................................................. 14/14

ok

In the test runner scripts for both tap and tape you will get lots of output including line numbers when an assertion fails.

running a tape test in a browser

First npm install -g browserify, then you can do:

$ browserify test.js > bundle.js
$ echo '<script src="bundle.js"></script>' > test.html

Then open test.html in a browser and look at the test output in the debugger. tape writes all its output to console.log() by default.

If you want to run your tests in a real headless browser locally, npm install -g testling then do:

$ browserify test.js | testling
TAP version 13
# defined-or
ok 1 empty arguments
ok 2 1 undefined
ok 3 2 undefined
ok 4 4 undefineds
ok 5 false[0]
ok 6 false[1]
ok 7 zero[0]
ok 8 zero[1]
ok 9 first arg
ok 10 second arg
ok 11 third arg

1..11
# tests 11
# pass  11

# ok

and your test will run in chrome or firefox headlessly, depending which you have installed on your system. The console.log() output is proxied from the browser to your stdout and the testling command generates an exit code by parsing the TAP output.

running a directory full of tape tests in a browser

To run multiple tests, just use a file glob:

$ browserify test/*.js | testling
TAP version 13
# defined-or
ok 1 empty arguments
ok 2 1 undefined
ok 3 2 undefined
ok 4 4 undefineds
ok 5 false[0]
ok 6 false[1]
ok 7 zero[0]
ok 8 zero[1]
ok 9 first arg
ok 10 second arg
ok 11 third arg
# (anonymous)
ok 12 should be equal

1..12
# tests 12
# pass  12

# ok

conclusion

If you need more complicated abstractions in your tests, just npm install them and require() them in your tests. Just be careful that the libraries you're importing also work in browsers.

tape shows that you don't actually need very much API to test your libraries in a powerful and flexible way that works in node and in browsers.

quick start guide
Create a github hook to run your tests on every push. Get a browser badge.
writing tests with tape
Write tests with a minimal test api that works in both node and browsers.
testing locally
Run your tests in node and your local browsers.
writing tests with mocha
Run tests in mocha for qunit, tdd, bdd, and exports-style tests.
module-driven development
Write code that is easier to maintain and easier to test with browserify.
dependency management
Use npm to manage your front-end dependencies.
advanced configuration
Read in-depth about the package.json "testling" field.
custom test libraries
Use your own test library by outputting TAP with `console.log()`.