discourse/test/javascripts/components/d-editor-test.js.es6

import componentTest from 'helpers/component-test';
import { withPluginApi } from 'discourse/lib/plugin-api';

moduleForComponent('d-editor', {integration: true});

componentTest('preview updates with markdown', {
  template: '{{d-editor value=value}}',

  test(assert) {
    assert.ok(this.$('.d-editor-button-bar').length);
    fillIn('.d-editor-input', 'hello **world**');

    andThen(() => {
      assert.equal(this.get('value'), 'hello **world**');
      assert.equal(this.$('.d-editor-preview').html().trim(), '<p>hello <strong>world</strong></p>');
    });
  }
});

componentTest('preview sanitizes HTML', {
  template: '{{d-editor value=value}}',

  test(assert) {
    fillIn('.d-editor-input', `"><svg onload="prompt(/xss/)"></svg>`);
    andThen(() => {
      assert.equal(this.$('.d-editor-preview').html().trim(), '<p>\"&gt;</p>');
    });
  }
});

componentTest('updating the value refreshes the preview', {
  template: '{{d-editor value=value}}',

  beforeEach() {
    this.set('value', 'evil trout');
  },

  test(assert) {
    assert.equal(this.$('.d-editor-preview').html().trim(), '<p>evil trout</p>');

    andThen(() => this.set('value', 'zogstrip'));
    andThen(() => assert.equal(this.$('.d-editor-preview').html().trim(), '<p>zogstrip</p>'));
  }
});

function jumpEnd(textarea) {
  textarea.selectionStart = textarea.value.length;
  textarea.selectionEnd = textarea.value.length;
  return textarea;
}

function testCase(title, testFunc) {
  componentTest(title, {
    template: '{{d-editor value=value}}',
    beforeEach() {
      this.set('value', 'hello world.');
    },
    test(assert) {
      const textarea = jumpEnd(this.$('textarea.d-editor-input')[0]);
      testFunc.call(this, assert, textarea);
    }
  });
}

function composerTestCase(title, testFunc) {
  componentTest(title, {
    template: '{{d-editor value=value composerEvents=true}}',
    beforeEach() {
      this.set('value', 'hello world.');
    },
    test(assert) {
      const textarea = jumpEnd(this.$('textarea.d-editor-input')[0]);
      testFunc.call(this, assert, textarea);
    }
  });
}

testCase(`selecting the space before a word`, function(assert, textarea) {
  textarea.selectionStart = 5;
  textarea.selectionEnd = 7;

  click(`button.bold`);
  andThen(() => {
    assert.equal(this.get('value'), `hello **w**orld.`);
    assert.equal(textarea.selectionStart, 8);
    assert.equal(textarea.selectionEnd, 9);
  });
});

testCase(`selecting the space after a word`, function(assert, textarea) {
  textarea.selectionStart = 0;
  textarea.selectionEnd = 6;

  click(`button.bold`);
  andThen(() => {
    assert.equal(this.get('value'), `**hello** world.`);
    assert.equal(textarea.selectionStart, 2);
    assert.equal(textarea.selectionEnd, 7);
  });
});

testCase(`bold button with no selection`, function(assert, textarea) {
  click(`button.bold`);
  andThen(() => {
    const example = I18n.t(`composer.bold_text`);
    assert.equal(this.get('value'), `hello world.**${example}**`);
    assert.equal(textarea.selectionStart, 14);
    assert.equal(textarea.selectionEnd, 14 + example.length);
  });
});

testCase(`bold button with a selection`, function(assert, textarea) {
  textarea.selectionStart = 6;
  textarea.selectionEnd = 11;

  click(`button.bold`);
  andThen(() => {
    assert.equal(this.get('value'), `hello **world**.`);
    assert.equal(textarea.selectionStart, 8);
    assert.equal(textarea.selectionEnd, 13);
  });

  click(`button.bold`);
  andThen(() => {
    assert.equal(this.get('value'), 'hello world.');
    assert.equal(textarea.selectionStart, 6);
    assert.equal(textarea.selectionEnd, 11);
  });
});

testCase(`bold with a multiline selection`, function (assert, textarea) {
  this.set('value', "hello\n\nworld\n\ntest.");

  andThen(() => {
    textarea.selectionStart = 0;
    textarea.selectionEnd = 12;
  });

  click(`button.bold`);
  andThen(() => {
    assert.equal(this.get('value'), `**hello**\n\n**world**\n\ntest.`);
    assert.equal(textarea.selectionStart, 0);
    assert.equal(textarea.selectionEnd, 20);
  });

  click(`button.bold`);
  andThen(() => {
    assert.equal(this.get('value'), `hello\n\nworld\n\ntest.`);
    assert.equal(textarea.selectionStart, 0);
    assert.equal(textarea.selectionEnd, 12);
  });
});

testCase(`italic button with no selection`, function(assert, textarea) {
  click(`button.italic`);
  andThen(() => {
    const example = I18n.t(`composer.italic_text`);
    assert.equal(this.get('value'), `hello world._${example}_`);

    assert.equal(textarea.selectionStart, 13);
    assert.equal(textarea.selectionEnd, 13 + example.length);
  });
});

testCase(`italic button with a selection`, function(assert, textarea) {
  textarea.selectionStart = 6;
  textarea.selectionEnd = 11;

  click(`button.italic`);
  andThen(() => {
    assert.equal(this.get('value'), `hello _world_.`);
    assert.equal(textarea.selectionStart, 7);
    assert.equal(textarea.selectionEnd, 12);
  });

  click(`button.italic`);
  andThen(() => {
    assert.equal(this.get('value'), 'hello world.');
    assert.equal(textarea.selectionStart, 6);
    assert.equal(textarea.selectionEnd, 11);
  });
});

testCase(`italic with a multiline selection`, function (assert, textarea) {
  this.set('value', "hello\n\nworld\n\ntest.");

  andThen(() => {
    textarea.selectionStart = 0;
    textarea.selectionEnd = 12;
  });

  click(`button.italic`);
  andThen(() => {
    assert.equal(this.get('value'), `_hello_\n\n_world_\n\ntest.`);
    assert.equal(textarea.selectionStart, 0);
    assert.equal(textarea.selectionEnd, 16);
  });

  click(`button.italic`);
  andThen(() => {
    assert.equal(this.get('value'), `hello\n\nworld\n\ntest.`);
    assert.equal(textarea.selectionStart, 0);
    assert.equal(textarea.selectionEnd, 12);
  });
});

testCase('link modal (cancel)', function(assert) {
  assert.equal(this.$('.insert-link.hidden').length, 1);

  click('button.link');
  andThen(() => {
    assert.equal(this.$('.insert-link.hidden').length, 0);
  });

  click('.insert-link button.btn-danger');
  andThen(() => {
    assert.equal(this.$('.insert-link.hidden').length, 1);
    assert.equal(this.get('value'), 'hello world.');
  });
});

testCase('link modal (simple link)', function(assert, textarea) {
  click('button.link');

  const url = 'http://eviltrout.com';

  fillIn('.insert-link input.link-url', url);
  click('.insert-link button.btn-primary');
  andThen(() => {
    assert.equal(this.$('.insert-link.hidden').length, 1);
    assert.equal(this.get('value'), `hello world.[${url}](${url})`);
    assert.equal(textarea.selectionStart, 13);
    assert.equal(textarea.selectionEnd, 13 + url.length);
  });
});

testCase('link modal auto http addition', function(assert) {
  click('button.link');
  fillIn('.insert-link input.link-url', 'sam.com');
  click('.insert-link button.btn-primary');
  andThen(() => {
    assert.equal(this.get('value'), `hello world.[sam.com](http://sam.com)`);
  });
});

testCase('link modal (simple link) with selected text', function(assert, textarea) {
  textarea.selectionStart = 0;
  textarea.selectionEnd = 12;

  click('button.link');
  fillIn('.insert-link input.link-url', 'http://eviltrout.com');
  click('.insert-link button.btn-primary');
  andThen(() => {
    assert.equal(this.$('.insert-link.hidden').length, 1);
    assert.equal(this.get('value'), '[hello world.](http://eviltrout.com)');
  });
});

testCase('link modal (link with description)', function(assert) {
  click('button.link');
  fillIn('.insert-link input.link-url', 'http://eviltrout.com');
  fillIn('.insert-link input.link-text', 'evil trout');
  click('.insert-link button.btn-primary');
  andThen(() => {
    assert.equal(this.$('.insert-link.hidden').length, 1);
    assert.equal(this.get('value'), 'hello world.[evil trout](http://eviltrout.com)');
  });
});

componentTest('advanced code', {
  template: '{{d-editor value=value}}',
  beforeEach() {
    this.siteSettings.code_formatting_style = '4-spaces-indent';
    this.set('value',
`
function xyz(x, y, z) {
  if (y === z) {
    return true;
  }
}
`   );
  },

  test(assert) {
    const textarea = this.$('textarea.d-editor-input')[0];
    textarea.selectionStart = 0;
    textarea.selectionEnd = textarea.value.length;

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`
    function xyz(x, y, z) {
      if (y === z) {
        return true;
      }
    }
`
      );
    });
  }

});

componentTest('code button', {
  template: '{{d-editor value=value}}',
  beforeEach() {
    this.siteSettings.code_formatting_style = '4-spaces-indent';
  },

  test(assert) {
    const textarea = jumpEnd(this.$('textarea.d-editor-input')[0]);

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`    ${I18n.t('composer.code_text')}`
      );

      this.set('value', "first line\n\nsecond line\n\nthird line");

      textarea.selectionStart = 11;
      textarea.selectionEnd = 11;
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`first line
    ${I18n.t('composer.code_text')}
second line

third line`
      );

      this.set('value', "first line\n\nsecond line\n\nthird line");
    });


    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`first line

second line

third line\`${I18n.t('composer.code_title')}\``
      );
      this.set('value', "first line\n\nsecond line\n\nthird line");
    });

    andThen(() => {
      textarea.selectionStart = 5;
      textarea.selectionEnd = 5;
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`first\`${I18n.t('composer.code_title')}\` line

second line

third line`
      );
      this.set('value', "first line\n\nsecond line\n\nthird line");
    });

    andThen(() => {
      textarea.selectionStart = 6;
      textarea.selectionEnd = 10;
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'), "first `line`\n\nsecond line\n\nthird line");
      assert.equal(textarea.selectionStart, 7);
      assert.equal(textarea.selectionEnd, 11);
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'), "first line\n\nsecond line\n\nthird line");
      assert.equal(textarea.selectionStart, 6);
      assert.equal(textarea.selectionEnd, 10);

      textarea.selectionStart = 0;
      textarea.selectionEnd = 23;
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'), "    first line\n\n    second line\n\nthird line");
      assert.equal(textarea.selectionStart, 0);
      assert.equal(textarea.selectionEnd, 31);
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'), "first line\n\nsecond line\n\nthird line");
      assert.equal(textarea.selectionStart, 0);
      assert.equal(textarea.selectionEnd, 23);
    });
  }
});

componentTest('code fences', {
  template: '{{d-editor value=value}}',
  beforeEach() {
    this.set('value', '');
  },

  test(assert) {
    const textarea = jumpEnd(this.$('textarea.d-editor-input')[0]);

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`\`\`\`
${I18n.t("composer.paste_code_text")}
\`\`\``
      );

      assert.equal(textarea.selectionStart, 4);
      assert.equal(textarea.selectionEnd, 27);

      this.set('value', 'first line\nsecond line\nthird line');

      textarea.selectionStart = 0;
      textarea.selectionEnd = textarea.value.length;
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`\`\`\`
first line
second line
third line
\`\`\`
`
      );

      assert.equal(textarea.selectionStart, textarea.value.length);
      assert.equal(textarea.selectionEnd, textarea.value.length);

      this.set('value', 'first line\nsecond line\nthird line');

      textarea.selectionStart = 0;
      textarea.selectionEnd = 0;
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`\`${I18n.t('composer.code_title')}\`first line
second line
third line`
      );

      assert.equal(textarea.selectionStart, 1);
      assert.equal(textarea.selectionEnd, I18n.t('composer.code_title').length + 1);

      this.set('value', 'first line\nsecond line\nthird line');

      textarea.selectionStart = 0;
      textarea.selectionEnd = 10;
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`\`first line\`
second line
third line`
      );

      assert.equal(textarea.selectionStart, 1);
      assert.equal(textarea.selectionEnd, 11);

      this.set('value', 'first line\nsecond line\nthird line');

      textarea.selectionStart = 0;
      textarea.selectionEnd = 23;
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'),
`\`\`\`
first line
second line
\`\`\`
third line`
      );

      assert.equal(textarea.selectionStart, 30);
      assert.equal(textarea.selectionEnd, 30);

      this.set('value', 'first line\nsecond line\nthird line');

      textarea.selectionStart = 6;
      textarea.selectionEnd = 17;
    });

    click('button.code');
    andThen(() => {
      assert.equal(this.get('value'), `first \n\`\`\`\nline\nsecond\n\`\`\`\n line\nthird line`);

      assert.equal(textarea.selectionStart, 27);
      assert.equal(textarea.selectionEnd, 27);
    });
  }
});


testCase('quote button', function(assert, textarea) {

  andThen(() => {
    textarea.selectionStart = 6;
    textarea.selectionEnd = 9;
  });

  click('button.quote');
  andThen(() => {
    assert.equal(this.get('value'), 'hello\n\n> wor\n\nld.');
    assert.equal(textarea.selectionStart, 7);
    assert.equal(textarea.selectionEnd, 12);
  });

  click('button.quote');

  andThen(() => {
    assert.equal(this.get('value'), 'hello\n\nwor\n\nld.');
    assert.equal(textarea.selectionStart, 7);
    assert.equal(textarea.selectionEnd, 10);
  });

  andThen(() => {
    textarea.selectionStart = 15;
    textarea.selectionEnd = 15;
  });

  click('button.quote');
  andThen(() => {
    assert.equal(this.get('value'), 'hello\n\nwor\n\nld.\n\n> Blockquote');
  });

});

testCase(`bullet button with no selection`, function(assert, textarea) {
  const example = I18n.t('composer.list_item');

  click(`button.bullet`);
  andThen(() => {
    assert.equal(this.get('value'), `hello world.\n\n* ${example}`);
    assert.equal(textarea.selectionStart, 14);
    assert.equal(textarea.selectionEnd, 16 + example.length);
  });

  click(`button.bullet`);
  andThen(() => {
    assert.equal(this.get('value'), `hello world.\n\n${example}`);
  });
});

testCase(`bullet button with a selection`, function(assert, textarea) {
  textarea.selectionStart = 6;
  textarea.selectionEnd = 11;

  click(`button.bullet`);
  andThen(() => {
    assert.equal(this.get('value'), `hello\n\n* world\n\n.`);
    assert.equal(textarea.selectionStart, 7);
    assert.equal(textarea.selectionEnd, 14);
  });

  click(`button.bullet`);
  andThen(() => {
    assert.equal(this.get('value'), `hello\n\nworld\n\n.`);
    assert.equal(textarea.selectionStart, 7);
    assert.equal(textarea.selectionEnd, 12);
  });
});

testCase(`bullet button with a multiple line selection`, function(assert, textarea) {
  this.set('value', "* Hello\n\nWorld\n\nEvil");

  andThen(() => {
    textarea.selectionStart = 0;
    textarea.selectionEnd = 20;
  });

  click(`button.bullet`);
  andThen(() => {
    assert.equal(this.get('value'), "Hello\n\nWorld\n\nEvil");
    assert.equal(textarea.selectionStart, 0);
    assert.equal(textarea.selectionEnd, 18);
  });

  click(`button.bullet`);
  andThen(() => {
    assert.equal(this.get('value'), "* Hello\n\n* World\n\n* Evil");
    assert.equal(textarea.selectionStart, 0);
    assert.equal(textarea.selectionEnd, 24);
  });
});

testCase(`list button with no selection`, function(assert, textarea) {
  const example = I18n.t('composer.list_item');

  click(`button.list`);
  andThen(() => {
    assert.equal(this.get('value'), `hello world.\n\n1. ${example}`);
    assert.equal(textarea.selectionStart, 14);
    assert.equal(textarea.selectionEnd, 17 + example.length);
  });

  click(`button.list`);
  andThen(() => {
    assert.equal(this.get('value'), `hello world.\n\n${example}`);
    assert.equal(textarea.selectionStart, 14);
    assert.equal(textarea.selectionEnd, 14 + example.length);
  });
});

testCase(`list button with a selection`, function(assert, textarea) {
  textarea.selectionStart = 6;
  textarea.selectionEnd = 11;

  click(`button.list`);
  andThen(() => {
    assert.equal(this.get('value'), `hello\n\n1. world\n\n.`);
    assert.equal(textarea.selectionStart, 7);
    assert.equal(textarea.selectionEnd, 15);
  });

  click(`button.list`);
  andThen(() => {
    assert.equal(this.get('value'), `hello\n\nworld\n\n.`);
    assert.equal(textarea.selectionStart, 7);
    assert.equal(textarea.selectionEnd, 12);
  });
});

testCase(`list button with line sequence`, function(assert, textarea) {
  this.set('value', "Hello\n\nWorld\n\nEvil");

  andThen(() => {
    textarea.selectionStart = 0;
    textarea.selectionEnd = 18;
  });

  click(`button.list`);
  andThen(() => {
    assert.equal(this.get('value'), "1. Hello\n\n2. World\n\n3. Evil");
    assert.equal(textarea.selectionStart, 0);
    assert.equal(textarea.selectionEnd, 27);
  });

  click(`button.list`);
  andThen(() => {
    assert.equal(this.get('value'), "Hello\n\nWorld\n\nEvil");
    assert.equal(textarea.selectionStart, 0);
    assert.equal(textarea.selectionEnd, 18);
  });
});

testCase(`heading button with no selection`, function(assert, textarea) {
  const example = I18n.t('composer.heading_text');

  click(`button.heading`);
  andThen(() => {
    assert.equal(this.get('value'), `hello world.\n\n## ${example}`);
    assert.equal(textarea.selectionStart, 14);
    assert.equal(textarea.selectionEnd, 17 + example.length);
  });

  textarea.selectionStart = 30;
  textarea.selectionEnd = 30;
  click(`button.heading`);
  andThen(() => {
    assert.equal(this.get('value'), `hello world.\n\n${example}`);
    assert.equal(textarea.selectionStart, 14);
    assert.equal(textarea.selectionEnd, 14 + example.length);
  });
});

testCase(`rule between things`, function(assert, textarea) {
  textarea.selectionStart = 5;
  textarea.selectionEnd = 5;

  click(`button.rule`);
  andThen(() => {
    assert.equal(this.get('value'), `hello\n\n----------\n world.`);
    assert.equal(textarea.selectionStart, 18);
    assert.equal(textarea.selectionEnd, 18);
  });
});

testCase(`rule with no selection`, function(assert, textarea) {
  click(`button.rule`);
  andThen(() => {
    assert.equal(this.get('value'), `hello world.\n\n----------\n`);
    assert.equal(textarea.selectionStart, 25);
    assert.equal(textarea.selectionEnd, 25);
  });

  click(`button.rule`);
  andThen(() => {
    assert.equal(this.get('value'), `hello world.\n\n----------\n\n\n----------\n`);
    assert.equal(textarea.selectionStart, 38);
    assert.equal(textarea.selectionEnd, 38);
  });
});

testCase(`rule with a selection`, function(assert, textarea) {
  textarea.selectionStart = 6;
  textarea.selectionEnd = 11;

  click(`button.rule`);
  andThen(() => {
    assert.equal(this.get('value'), `hello \n\n----------\n.`);
    assert.equal(textarea.selectionStart, 19);
    assert.equal(textarea.selectionEnd, 19);
  });
});

testCase(`doesn't jump to bottom with long text`, function(assert, textarea) {

  let longText = 'hello world.';
  for (let i=0; i<8; i++) {
    longText = longText + longText;
  }
  this.set('value', longText);

  andThen(() => {
    $(textarea).scrollTop(0);
    textarea.selectionStart = 3;
    textarea.selectionEnd = 3;
  });

  click('button.bold');
  andThen(() => {
    assert.equal($(textarea).scrollTop(), 0, 'it stays scrolled up');
  });
});

componentTest('emoji', {
  template: '{{d-editor value=value}}',
  beforeEach() {
    // Test adding a custom button
    withPluginApi('0.1', api => {
      api.onToolbarCreate(toolbar => {
        toolbar.addButton({
          id: 'emoji',
          group: 'extras',
          icon: 'smile-o',
          action: 'emoji'
        });
      });
    });
    this.set('value', 'hello world.');
  },
  test(assert) {
    assert.equal($('.emoji-modal').length, 0);

    jumpEnd(this.$('textarea.d-editor-input')[0]);
    click('button.emoji');
    andThen(() => {
      assert.equal($('.emoji-modal').length, 1);
    });

    click('a[data-group-id=0]');
    click('a[title=grinning]');

    andThen(() => {
      assert.ok($('.emoji-modal').length === 0);
      assert.equal(this.get('value'), 'hello world.:grinning:');
    });
  }
});

testCase("replace-text event by default", function(assert) {
  this.set('value', "red green blue");

  andThen(() => {
    this.container.lookup('app-events:main').trigger('composer:replace-text', 'green', 'yellow');
  });

  andThen(() => {
    assert.equal(this.get('value'), 'red green blue');
  });
});

composerTestCase("replace-text event for composer", function(assert) {
  this.set('value', "red green blue");

  andThen(() => {
    this.container.lookup('app-events:main').trigger('composer:replace-text', 'green', 'yellow');
  });

  andThen(() => {
    assert.equal(this.get('value'), 'red yellow blue');
  });
});


(() => {
  // Tests to check cursor/selection after replace-text event.
  const BEFORE = 'red green blue';
  const NEEDLE = 'green';
  const REPLACE = 'yellow';
  const AFTER = BEFORE.replace(NEEDLE, REPLACE);

  const CASES = [
    {
      description: 'cursor at start remains there',
      before: [0, 0],
      after: [0, 0]
    },{
      description: 'cursor before needle becomes cursor before replacement',
      before: [BEFORE.indexOf(NEEDLE), 0],
      after: [AFTER.indexOf(REPLACE), 0]
    },{
      description: 'cursor at needle start + 1 moves behind replacement',
      before: [BEFORE.indexOf(NEEDLE) + 1, 0],
      after: [AFTER.indexOf(REPLACE) + REPLACE.length, 0]
    },{
      description: 'cursor at needle end - 1 stays behind replacement',
      before: [BEFORE.indexOf(NEEDLE) + NEEDLE.length - 1, 0],
      after: [AFTER.indexOf(REPLACE) + REPLACE.length, 0]
    },{
      description: 'cursor behind needle becomes cursor behind replacement',
      before: [BEFORE.indexOf(NEEDLE) + NEEDLE.length, 0],
      after: [AFTER.indexOf(REPLACE) + REPLACE.length, 0]
    },{
      description: 'cursor at end remains there',
      before: [BEFORE.length, 0],
      after: [AFTER.length, 0]
    },{
      description: 'selection spanning needle start becomes selection until replacement start',
      before: [BEFORE.indexOf(NEEDLE) - 1, 2],
      after: [AFTER.indexOf(REPLACE) - 1, 1]
    },{
      description: 'selection spanning needle end becomes selection from replacement end',
      before: [BEFORE.indexOf(NEEDLE) + NEEDLE.length - 1, 2],
      after: [AFTER.indexOf(REPLACE) + REPLACE.length, 1]
    },{
      description: 'selection spanning needle becomes selection spanning replacement',
      before: [BEFORE.indexOf(NEEDLE) - 1, NEEDLE.length + 2],
      after: [AFTER.indexOf(REPLACE) - 1, REPLACE.length + 2]
    },{
      description: 'complete selection remains complete',
      before: [0, BEFORE.length],
      after: [0, AFTER.length]
    }
  ];

  function setSelection(textarea, [start, len]) {
    textarea.selectionStart = start;
    textarea.selectionEnd = start + len;
  }

  function getSelection(textarea) {
    const start = textarea.selectionStart;
    const end = textarea.selectionEnd;
    return [start, end - start];
  }

  function formatTextWithSelection(text, [start, len]) {
    return [
      '"',
      text.substr(0, start),
      '<',
      text.substr(start, len),
      '>',
      text.substr(start+len),
      '"',
    ].join('');
  }

  for (let i = 0; i < CASES.length; i++) {
    const CASE = CASES[i];
    composerTestCase(`replace-text event: ${CASE.description}`, function(assert, textarea) {
      this.set('value', BEFORE);
      setSelection(textarea, CASE.before);
      andThen(() => {
        this.container.lookup('app-events:main').trigger('composer:replace-text', 'green', 'yellow');
      });
      andThen(() => {
        let expect = formatTextWithSelection(AFTER, CASE.after);
        let actual = formatTextWithSelection(this.get('value'), getSelection(textarea));
        assert.equal(actual, expect);
      });
    });
  }
})();