Thursday, December 12, 2013

C# Puzzle No.23 (intermediate)

Closures are interesting and helpful. In short, closure is a function that can be exposed to the outside world that captures part of its external environment, even though the environment could be private to outside world.

This puzzle involves following short snippet inspired by the Javascript: Definitive Guide book

// create array of 10 functions
static Func<int>[] constfuncs()
    Func<int>[] funcs = new Func<int>[10];
    for ( var i = 0; i < 10; i++ )
        funcs[i] = () => i;
    return funcs;
var funcs = constfuncs();
for ( int i = 0; i < 10; i++ )
    Console.WriteLine( funcs[i]() );
// output:
// 10
// 10
// ...
// 10

Side note: closures in Javascript work very similar and the output of corresponding Javascript snippet would be the same

function constfuncs() {
  var funcs = [];
  for(var i = 0; i < 10; i++)
    funcs[i] = function() { return i; };
  return funcs;
var funcs = constfuncs();
for ( var i = 0; i < 10; i++ )
    console.log( funcs[i]() );

End of side note

Your task here is not only to explain the behavior (easy part) but also correct the inner loop of the constfuncs method so that the code outputs


More specifically, you are allowed to modify only this line of code

funcs[i] = () => i;

You are free to propose a solution for the JavaScript version as well. The book doesn’t provide one, if you are interested.

Monday, December 2, 2013

Basic tests in Apache JMeter part 2/2

In the previous post we have recorded a basic JMeter test. This time we start with adding an assertion to validate test results.

Multiple assertions can be added to each requests. However, in our simple demo we need a single assertion on the last request just to check whether or not the user is succesfully logged into the application.

Right click the last request and add a Response Assertion. In my particular case, the last page renders the message with the logged in user name. In the response assertion page I add a Pattern to test, the message I expect to see at the last page of the session. If you run the test now it will most probably fail, as the controller lacks the cookie manager, so add one (Add/Config Element/HTTP Cookie Manager) and check the “Clear cookies at each iteration?” checkbox at the cookie manager configuration tab.

The screenshot shows the Response Assertion configuration tab with the pattern to test set to my custom expected message (it says “The logged in user is <username>” in Polish).

Response Assertion with custom text If you run the test now and check the results tree, you will most probably see a green icon beside all requests which is a notification of success. Play with the assertion pattern to verify that the assertion really works – a failed assertion marks the request with a red icon at the results tree view.

The last element of the tutorial is modification of POST requests. In my particular scenario, one of the responses returns a SAML token which should be posted in the very next request. However, the recorded session replays the same token every time, the token that was returned in the response body during the recording of my session. This is because JMeter only records and replays requests and it has no knowledge that one of returned parameters should be POSTed in the next request. Because of that, my recorded session works correctly for few hours and then the SAML token will no longer be accepted by the target server (the server will complain that the token is too old).

I start by locating the request that returns the SAML token. I can use the View Results Tree which shows detailed requests and responses. Here it is, the SAML returned in the response of one of my Default.aspx pages:

SAML token response

I right click the node corresponding to the request under my controller and add a post processor (Add/Postprocessors/Regular Expression Extractor). The postprocessor allows me to provide a regular expression and assign its match value to a variable I can use in consecutive requests. At the postprocessor configuration tab I provide necessary parameters: name – SAMLToken, regular expression – name=”wresult” value=”(.*)” /><input (to capture the whole SAML token), template – $1$, match – 1, default value – NOVALUE (more on the extractor here).

Extractor configuration

Then I go to the very next request (LoginPage.aspx) and at the Parameters tab I inspect the list of posted parameters. In my example there are three parameters sent to the server, wa, wresult and wctx, all three have fixed values taken from the recorded session. I am going to modify the wresult parameter to refer to the newly created variable, SAMLToken.

I have two options, I can provide a bare value (${SAMLToken}) or an unescaped value (${__unescapeHtml(${SAMLToken})}, I choose the latter.

Referencing the parameter And this is it, the token value read from the response is correctly referenced in the consecutive request. There are other JMeter fuctions that can be used there.

I can now configure the thread group to simulate more concurrent users and verify the correctness and the performance under different load conditions.

Basic tests in Apache JMeter part 1/2

Apache JMeter is a fine tool for different types of web tests – compatibility, performance, integration. This post is about recording, running and parametrizing basic tests.

First, start by running JMeter, you start with an empty Test Plan. Give it a name and add a Thread Group to the Test Plan (right click the Test Plan node and select Add/Threads/Thread Group).

Thread Group Thread Group represents a set of “users”. As you can see, you can modify the number of threads (users) and the ramp-up period. This is handy for testing your application for multiple concurrent clients.

Next step would be to set up an HTTP Proxy Server and a Recording Controller. These two will allow me to “record” the browser’s session instead of creating all requests manually.

Right-click the WorkBench node and add a Non-Test Element, HTTP Proxy Server. Add a Recording Controller to the Thread Group. In the HTTP Proxy’s settings tab, select the newly created Recording Controller as the target controller.

Target Controller Now start the proxy (Start button at the bottom of the settings tab), open up my web browser (any browser will do) and set the proxy to http://localhost:8080. If you are on Firefox, remember to set the proxy for each protocol (including HTTPS) (Tools/Options/Advanced/Network):

Firefox network setup

Now navigate to a web site you want to test. Each action is recorded under the recording controller.

To be able to replay the sequence of tests and see the results, add a listener to the thread group, the View Results Tree listener. Now you can click the Start button (or select Run/Start from the menu) and click your listener to see the replayed session. Use the Clear All button (Run/Clear All) to clear the listener.

Recorded session in the tree listener

In the next post we will create basic assertions and also modify the flow so that values returned from requests are used in consecutive posts.