Add unit tests to narrow.js.

This includes slightly invasive, but harmless, changes to
production code.

(imported from commit 847557c11088b75c836cc399d0af75353a8faa3a)

static/js/narrow.js

@@ -209,6 +209,11 @@ exports.Filter = Filter;
 
 var current_filter;
 
+// A small concession to unit testing follows:
+exports._set_current_filter = function (filter) {
+    current_filter = filter;
+};
+
 exports.active = function () {
     return current_filter !== undefined;
 };

static/js/subs.js

@@ -863,3 +863,6 @@ exports.show_and_focus_on_narrow = function () {
 return exports;
 
 }());
+if (typeof module !== 'undefined') {
+    module.exports = subs;
+}

tools/test-js-with-node

@@ -11,5 +11,6 @@ NODEJS=$(which nodejs || which node)
 $NODEJS util.js
 $NODEJS message_list.js
 $NODEJS message_tour.js
+$NODEJS narrow.js
 $NODEJS unread.js
 $NODEJS search_suggestion.js

zerver/tests/frontend/node/narrow.js

@@ -0,0 +1,36 @@
+var assert = require('assert');
+
+(function set_up_dependencies () {
+    global._ = require('third/underscore/underscore.js');
+    global.util = require('js/util.js');
+    global.narrow = require('js/narrow.js');
+    global.$ = function () {}; // for subs.js
+    global.subs = require('js/subs.js');
+}());
+
+var narrow = global.narrow;
+
+(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 narrow.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 narrow.Filter(operators));
+
+    assert.deepEqual(narrow.operators(), canonical_operators);
+}());