old_contents: var assert = require('assert');
  
  (function set_up_dependencies () {
      global._ = require('third/underscore/underscore.js');
      global.util = require('js/util.js');
      global.Dict = require('js/dict.js');
      global.narrow = require('js/narrow.js');
      global.stream_data = require('js/stream_data.js');
      global.Filter = require('js/filter.js');
  }());
  
  var narrow = global.narrow;
  var Filter = global.Filter;
  
  (function test_parse_and_unparse() {
      var string ='stream:Foo topic:Bar yo';
      var operators = [['stream', 'Foo'], ['topic', 'Bar'], ['search', 'yo']];
  
      assert.deepEqual(narrow.parse(string), operators);
  
      string = 'stream:foo topic:bar yo';
      assert.deepEqual(narrow.unparse(operators), string);
  }());
  
  (function test_stream() {
      var operators = [['stream', 'Foo'], ['topic', 'Bar'], ['search', 'yo']];
      narrow._set_current_filter(new Filter(operators));
  
      assert.equal(narrow.stream(), 'foo');
  }());
  
  (function test_operators() {
      var operators = [['stream', 'Foo'], ['topic', 'Bar'], ['search', 'yo']];
      var canonical_operators = [['stream', 'foo'], ['topic', 'bar'], ['search', 'yo']];
      narrow._set_current_filter(new Filter(operators));
  
      assert.deepEqual(narrow.operators(), canonical_operators);
  }());
  
new_contents: var assert = require('assert');
  
  (function set_up_dependencies () {
      global._ = require('third/underscore/underscore.js');
      global.util = require('js/util.js');
      global.Dict = require('js/dict.js');
      global.narrow = require('js/narrow.js');
      global.stream_data = require('js/stream_data.js');
      global.Filter = require('js/filter.js');
  }());
  
  var narrow = global.narrow;
  var Filter = global.Filter;
  
  (function test_parse_and_unparse() {
      var string ='stream:Foo topic:Bar yo';
      var operators = [['stream', 'Foo'], ['topic', 'Bar'], ['search', 'yo']];
  
      assert.deepEqual(narrow.parse(string), operators);
  
      string = 'stream:foo topic:bar yo';
      assert.deepEqual(narrow.unparse(operators), string);
  }());
  
  (function test_stream() {
      var operators = [['stream', 'Foo'], ['topic', 'Bar'], ['search', 'yo']];
      narrow._set_current_filter(new Filter(operators));
  
      assert.equal(narrow.stream(), 'foo');
  }());
  
  (function test_operators() {
      var operators = [['stream', 'Foo'], ['topic', 'Bar'], ['search', 'yo']];
      var canonical_operators = [['stream', 'foo'], ['topic', 'bar'], ['search', 'yo']];
      narrow._set_current_filter(new Filter(operators));
  
      assert.deepEqual(narrow.operators(), canonical_operators);
  }());
  
  (function test_set_compose_defaults() {
      var operators = [['stream', 'Foo'], ['topic', 'Bar']];
      narrow._set_current_filter(new Filter(operators));
  
      var opts = {};
      narrow.set_compose_defaults(opts);
      assert.equal(opts.stream, 'foo');
      assert.equal(opts.subject, 'bar');
  }());
  
subject: Add unit test for narrow.set_compose_defaults().