chai plugin to check if object tree contains some subtree

     chai.use(function(chai, utils) {
            function containsProperties(expected) {
                var actual = this._obj;
                var success = true;

                if(!utils.flag(this, 'deep')) {
                    if(Array.isArray(expected)) {
                        this.assert(success = expected.subtract(Object.extended(actual).select(expected).keys()).length === 0, "expected "+JSON.stringify(actual)+" to have "+JSON.stringify(expected));
                    } else {
                        this.assert(success = Object.extended(actual).select(Object.keys(expected)).equals(expected), "expected "+JSON.stringify(actual)+" to have "+JSON.stringify(expected));
                    }
                } else {
                    (function havePropertiesTree(actual, expected) {
                        if(!success) return;
                        if(typeof actual !== "object") {
                            if(actual != expected) {
                                success = false;
                            }
                        } else {
                            if(Object.keys(expected).subtract(Object.keys(actual)).length === 0) {
                                Object.keys(expected).forEach(function(v, k) {
                                    havePropertiesTree(actual[k], expected[k]);
                                });
                            } else {
                                success = false;
                            }
                        }
                    })(actual, expected);
                    
                    this.assert(success, "expected "+actual+" to contain "+expected+" as subtree");
                }
                return success;
            }            
            chai.Assertion.addMethod('properties', containsProperties);
            
            chai.Assertion.addMethod('calledWithObjectWithProperties', function(expected) {
                var spy = this._obj;
                this.assert(spy.callCount, "expected to be called but it wasn't");
                var i;    
                for(i = 0; i < spy.callCount; i++) {
                    var args = spy.args[i];
                    var actual = args[0];
                    console.info(containsProperties.call({ _obj: actual, assert: function() {} }, expected));
                    if(containsProperties.call({ _obj: actual, assert: function() {} }, expected)) {
                        break;
                    }
                }
                this.assert(i < spy.callCount, "expected to be called with "+JSON.stringify(expected)+" but got "+JSON.stringify(spy.args));
            });
        });