node tests: Add with_stub() helper.

frontend_tests/zjsunit/index.js

@@ -19,6 +19,10 @@ global.patch_builtin = namespace.patch_builtin;
 global.add_dependencies = namespace.add_dependencies;
 global.stub_out_jquery = namespace.stub_out_jquery;
 
+// Set up stub helpers.
+var stub = require('./stub.js');
+global.with_stub = stub.with_stub;
+
 // Set up helpers to render templates.
 var render = require('./render.js');
 global.make_sure_all_templates_have_been_compiled =

frontend_tests/zjsunit/stub.js

@@ -0,0 +1,52 @@
+var stub = (function () {
+
+var _ = require('node_modules/underscore/underscore.js');
+var exports = {};
+
+// Stubs don't do any magical modifications to your namespace.  They
+// just provide you a function that records what arguments get passed
+// to it.  To use stubs as something more like "spies," use something
+// like set_global() to override your namespace.
+
+exports.make_stub = function () {
+    var self = {};
+    self.num_calls = 0;
+
+    self.f = function () {
+        self.last_call_args = _.clone(arguments);
+        self.num_calls += 1;
+        return true;
+    };
+
+    self.get_args = function () {
+        var param_names = arguments;
+        var result = {};
+
+        _.each(param_names, function (name, i) {
+            result[name] = self.last_call_args[i];
+        });
+
+        return result;
+    };
+
+    return self;
+};
+
+exports.with_stub = function (f) {
+    var stub = exports.make_stub();
+    f(stub);
+    assert.equal(stub.num_calls, 1);
+};
+
+(function test_ourselves() {
+    exports.with_stub(function (stub) {
+        stub.f('blue', 42);
+        var args = stub.get_args('color', 'n');
+        assert.equal(args.color, 'blue');
+        assert.equal(args.n, 42);
+    });
+}());
+
+return exports;
+}());
+module.exports = stub;