Import modules
const assert = require('assert');
const jsc = require('jsverify');
const jscCommands = require('jsverify-commands');
Declare commands
play:
- unavailable until at least one track has been added to the player
- put the player in "play mode"
pause:
- put the player in "pause mode"
next:
- do not impact the mode: play keeps playing, pause keeps pausing
- in case of multiple tracks switch to next track
- otherwise keep playing the same track
add track:
- do not impact the mode: play keeps playing, pause keeps pausing
- in case of empty player before the command, switch to added track
- otherwise keep the same track
function PlayCommand() {
this.check = model => model.num_tracks > 0;
this.run = function(player, model) {
model.is_playing = true;
player.play();
return player.is_playing();
};
this.name = `Play`;
}
function PauseCommand() {
this.check = model => true;
this.run = function(player, model) {
model.is_playing = false;
player.pause();
return !player.is_playing();
};
this.name = `Pause`;
}
function NextCommand() {
this.check = model => true;
this.run = function(player, model) {
const track_before = player.track_name();
player.next();
if (model.is_playing !== player.is_playing()) {
return false; // should not change playing status
}
if (model.num_tracks <= 1) {
return track_before === player.track_name(); // keep playing the same
}
else {
return track_before !== player.track_name(); // go to another track
}
};
this.name = `Next`;
}
function AddTrackCommand(name, position) {
this.check = model => !model.tracks_already_seen.hasOwnProperty(name);
this.run = function(player, model) {
++model.num_tracks;
model.tracks_already_seen[name] = undefined;
const track_before = player.track_name();
player.add_track(name, position % model.num_tracks);
if (model.is_playing !== player.is_playing()) {
return false; // should not change playing status
}
if (model.num_tracks === 1) {
return player.track_name() === name;
}
return track_before === player.track_name();
};
this.name = `AddTrack(${name}, ${position})`;
}
Music player implementation
function MusicPlayer() {
let tracks = [];
let is_playing = false;
let playing_idx = 0;
this.is_playing = () => is_playing;
this.track_name = () => tracks[playing_idx];
this.play = () => is_playing = true;
this.pause = () => is_playing = false;
this.add_track = (name, position) => {
tracks = tracks.slice(0, position).concat(name).concat(tracks.slice(position));
if (tracks.length !== 1 && playing_idx >= position) {
++playing_idx;
}
};
this.next = () => {
if (++playing_idx >= tracks.length)
{
playing_idx = 0;
}
};
}
Music player model implementation
function MusicPlayerModel() {
this.is_playing = false
this.num_tracks = 0;
this.tracks_already_seen = {};
}
Fake mocha implementation (for RunKit purpose only)
const describe = (name, f) => f();
const it = async (name, f) => {
try { await f(); console.log(`${name}: success`); }
catch (err) { console.log(`${name}: failed with error`); console.log(err); }
};
Your tests go there
describe('MusicPlayer', function() {
it('should follow specifications', function() {
const commands = jscCommands.commands(
jscCommands.command(PlayCommand),
jscCommands.command(PauseCommand),
jscCommands.command(NextCommand),
jscCommands.command(AddTrackCommand, jsc.string, jsc.nat));
const warmup = () => new Object({
state: new MusicPlayer(),
model: new MusicPlayerModel()
});
const teardown = () => {};
const settings = {
metrics: true,
verbose: true
};
return jscCommands.assertForall(commands, warmup, teardown, settings);
});
});
Created from: https://npm.runkit.com/jsverify-commands
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