Based on TextReporter proposed on Stackoverflow: http://stackoverflow.com/questions/13366318/how-to-return-jasmine-unit-test-results-as-a-string

jasmine_on_rhino_02

TextReporter.prototype = new jasmine.Reporter();

TextReporter.prototype.onRunnerFinished = function (callback) {
    this.callbackEnd = callback;
};

TextReporter.prototype.reportRunnerResults = function (runner) {        
    // When all the spec are finished //
    var result = runner.results();

    this.textResult += "Test results :: (" + result.passedCount + "/" + result.totalCount + ") :: " + (result.passed() ? "passed" : "failed");
    this.textResult += "\r\n";

    if (this.callbackEnd) {
        this.callbackEnd(this.textResult);
    }
};

TextReporter.prototype.reportSuiteResults = function (suite) {
    // When a group of spec has finished running //
    var result = suite.results();
    var description = suite.description;
};

TextReporter.prototype.reportSpecResults = function(spec) {
    // When a single spec has finished running //
    var result = spec.results();
    var that = this;

    that.textResult += "Spec :: " + spec.description + " :: " + (result.passed() ? "passed" : "failed");
    that.textResult += "\r\n";
    
    /**** Added to report Error-Mesages during the test execution ***/
    if (!result.passed()) {
        spec.results().getItems().forEach(function (item) {
            if (!item.passed()) {
                that.textResult += "\t" +item.message;
                that.textResult += "\r\n";
            }
        });
    }
};