libs/mocha/should.js
function(constructor, desc){
        var name = constructor.name;
        this.assert(
            this.obj instanceof constructor
            , function(){ return 'expected ' + this.inspect + ' to be an instance of ' + name + (desc ? " | " + desc : "") }
            , function(){ return 'expected ' + this.inspect + ' not to be an instance of ' + name + (desc ? " | " + desc : "") });
        return this;
    }
function(constructor, desc){
        var name = constructor.name;
        this.assert(
            this.obj instanceof constructor
            , function(){ return 'expected ' + this.inspect + ' to be an instance of ' + name + (desc ? " | " + desc : "") }
            , function(){ return 'expected ' + this.inspect + ' not to be an instance of ' + name + (desc ? " | " + desc : "") });
        return this;
    }
function ( constructor , desc ) { var name = constructor . name ; this . assert ( this . obj instanceof constructor , function ( ) { return 'expected ' + this . inspect + ' to be an instance of ' + name + ( desc ? " | " + desc : "" ) } , function ( ) { return 'expected ' + this . inspect + ' not to be an instance of ' + name + ( desc ? " | " + desc : "" ) } ) ; return this ; }
Assert instanceof.

@param {Function} constructor
@param {String} description
@api public
Assert instanceof .