XPath in soapUI Part 3: Common XPath Functions

XPath supports quite a few functions that can be used to make your soapUI assertions even more sophisticated, including functions for different data types, aggregate functions to perform calculations across multiple values, etc.  In this post I'll look at a few basic functions with some examples; for a more extensive list I recommend this page at w3schools.com.  The examples reference the same sample project used in the last few posts, targeting a web service that returns data about holidays; you can download the project here if you haven't done so already.   The post also assumes you're familiar with namespaces, namespace prefixes, and basic XPath syntax, covered in previous posts.

Count() and Numeric Functions

The count() function (not too surprisingly) counts the number of matches found for a given expression.  For example, the following XPath expression counts the number of Holiday elements returned in the GetHolidaysAvailable test response; we could use it in an assertion to confirm that 24 holidays are returned:

count(//Holidays)

There are several numeric functions similar to the count() function that perform operations on expressions that return multiple matches.  For example, Holidays elements returned by the GetHolidaysAvailable test request have a numeric rowOrder attribute.  We can use the following functions to find their minimum, maximum, average, and sum:

min(//Holidays/@msdata:rowOrder)   (returns 0.0)
max(//Holidays/@msdata:rowOrder)   (returns 23.0)
avg(//Holidays/@msdata:rowOrder)   (returns 11.5)
sum(//Holidays/@msdata:rowOrder)   (returns 276.0)

String Functions

There are quite a few XPath functions for working with string data.  The contains(), starts-with(), and ends-with() functions each take two strings as their arguments; the first string (typically the result of an XPath expression) is tested accordingly for the presence of the second string.  For example, run the following XPath assertion against the GetHolidaysAvailable response:

contains(//Holidays[6]/Name , 'Patrick')   (returns true)

The XPath expression //Holidays[6]/Name evaluates to "St. Patrick's Day" (the Name of the sixth Holidays element in the response).  As the first argument to the contains() function, the string "St. Patrick's Day" is checked to see if it contains the second argument, the string "Patrick".  Consequently, the function returns the Boolean true.

Some example expressions using the starts-with() and ends-with() functions:

starts-with(//Holidays[8]/Key , 'GOOD_')   (returns true)
ends-with(//Holidays[13]/Name , 'Mayo')   (returns true)

Date Functions

XPath also provides some functions for working with dates, including functions to extract individual date/time components (months, years, minutes, etc.) from date and time values.  Here are examples we could use with the GetHolidaysForYear test request to confirm the month and day of Cinco de Mayo:

month-from-dateTime(//Holidays[Name = 'Cinco de Mayo']/Date)   (returns 5)
day-from-dateTime(//Holidays[Name = 'Cinco de Mayo']/Date)   (returns 5)

There are corresponding functions to retrieve the year, hours, minutes, or seconds from a full date and time value-- year-from-dateTime(), minutes-from-dateTime(), etc.-- plus functions to do the same with date- or time-only values-- year-from-date(), month-from-date(), hours-from-time(), seconds-from-time(), and so on.

Not() Function

In the last post, we saw that it's possible to use the logical operators and and or with XPath expressions.  The not() logical function takes an expression that results in a Boolean value and negates it, returning true if the original expression evaluated to false or false if the original expression evaluated to true. Not() is frequently used with the count() function to check that a given condition doesn't exist in test response XML.

For example, the GetHolidaysForYear test request returns holidays for a specified year.  One check we might want to do is to confirm that all of the dates are indeed within the specified year.  We know that no matter how many holidays are returned, zero holidays should be returned that don't fall in the specified year (we'll use 2013 in this case).  Here's a function that uses count(), not(), starts-with(), and logical operators to confirm that at least one holiday is returned (to make sure we're not just counting zero elements to begin with-- which would indicate something else is going wrong) and none of them fall outside 2013:

count(//Holidays) > 0 and count(//Holidays[not(starts-with(Date , '2013'))]) = 0   (returns true)

The first half of the assertion (before the and operator) should be pretty self-explanatory, but let's analyze the second part from the inside out, beginning with the starts-with() function, which checks the value of the Date element (as a string) to see if it begins with "2013".  The result of the starts-with function, a Boolean value, is negated by the not() function.  All of this is used as a predicate (within brackets) to target certain Holidays elements-- i.e., return only those Holidays elements with Date child elements that don't start with "2013".  Finally, matches found for that expression are counted by the count() function.  As we expected, the result of the count() function is 0-- none of our Holidays elements have dates that don't fall in 2013.

The example illustrates one of the potential pitfalls when working with longer, more complex expressions and multiple functions-- navigating the tangle of brackets and parentheses.  If you receive an "Invalid XPath expression" error trying to evaluate a complex expression like this, be sure to double-check the order and count (always in opening and closing pairs) of parentheses and brackets.  Also, if you get stuck building an expression with nested functions, you may find it helpful to back up and try working from the inside out, if possible, checking to make sure each part works by itself before putting all the pieces together.

In the next post, we'll look at using XPath with property transfers in soapUI.

XPath in soapUI Part 2: More Complex XPath Expressions

In the last post we looked at a simple example of an XPath assertion in soapUI-- in fact, we could have used a basic Contains assertion to accomplish pretty much the same thing.  In this post, we'll see a little more of the power of XPath and work on some more complex expressions.

Using the same sample project we used in the last post, let's look at the GetHolidaysForYear test case and test request.  Run it and look at the response XML:

An excerpt from the GetHolidaysForYear response XML
Where the GetHolidayDate request we looked at in the last post essentially returned one significant node, there are multiple nodes in which we could be interested here; consequently, there are some extra layers of complexity to deal with in our XPath expression.  Let's say we want to confirm the correct date is reflected for Valentine's Day in 2013, for example.  There are multiple Holidays elements; our XPath expression has to identify which one corresponds to Valentine's Day and check the value of its Date child element.

Create a new XPath assertion and click the Declare button to have soapUI automatically generate namespace declarations.  You may notice an odd thing here: one of our declared namespaces (for prefix "ns1") is an empty string:

Namespace declarations auto-generated by soapUI
If you look again at the response XML, you'll see there is a namespace defined (without a prefix) as an empty string in the NewDataSet opening tag.  This appears to be a negation of an earlier namespace definition in the GetHolidaysForYearResponse tag-- without this empty string namespace defined for the NewDataSet element, it would inherit the namespace defined for the GetHolidaysForYearResponse element ("http://www.27seconds.com/Holidays/").  The upshot: for the NewDataSet element (and any children without their own prefixes) we actually don't have to use any namespace prefix in our XPath expressions.

Now we have to figure out how to specify the Holidays element in our response that corresponds to Valentine's Day.  There are a few ways of doing this.  One pretty straightforward way is through the use of an index, placed within brackets after the Holidays element in our expression.  Note that with XPath, index numbers are 1-based as opposed to 0-based-- the first instance has index 1, the next has index 2, etc.  Valentine's Day is the 4th holiday reflected in the response, so we can construct our XPath assertion like this:

//Holidays[4]/Date

As you'll remember from the last post, "//Holidays" signifies that we're looking for a Holidays element anywhere (at any level in the tree) in the response XML.  The "[4]" following the name of the Holidays element references the fourth instance of the element occurring in the response.  Finally, "/Date" indicates that we're looking for the value of a Date element-- but note the use of a single-slash here instead of a double-slash: this limits our results to a Date element that's a child of the element before the slash.  The expression is equivalent to saying, "Return the value of the Date element that's a direct child of the fourth Holidays element."  Click the "Select from current" button to evaluate the expression, and it should return the expected date of "2013-02-14T00:00:00-05:00".

Of course, if an operation doesn't always return its data in the same order, using an index may not be sufficient.  You can use other types of expressions within the brackets to identify a particular occurrence of an element.  For example:

//Holidays[Name = "Valentine's Day"]/Date

This XPath expression isn't much different from the previous one (in fact, it evaluates to the same value), but instead of an index it uses a comparison operation within the brackets.  This expression finds the instance of a Holidays element that has a Name child element with the value "Valentine's Day", and then returns the value of the Date element for that instance.

You can also work with XML attributes, data specified within a tag as opposed to between matching tags.  For example, each Holidays element has a unique attribute called rowOrder that can be used to identify a particular instance.  We can use the following expression to get the Date value for Cinco de Mayo:

//Holidays[@msdata:rowOrder = "10"]/Date

Just as above, we're using the expression in the brackets to identify a particular instance of a Holidays element.  The "@" symbol indicates that we're looking for an attribute and not a standard element.  Note that we have to be careful with namespace prefixes here-- unlike the Holidays and Date elements, the rowOrder attribute has its own namespace prefix in the response XML and therefore requires a corresponding prefix ("msdata") in our XPath expression.

In addition to the "=" (equals) operator, XPath supports all the comparison operators you might expect: "!=" (not equals), ">" (greater than), "<" (less than), ">=" (greater than or equal to), and "<=" (less than or equal to).  Additionally, you can use these comparison operators in conjunction with "and" and "or"-- some examples:

//Holidays[@diffgr:id = "Holidays17" and @msdata:rowOrder <= 20]/Key   (evaluates to "LABOR")

//Holidays[@msdata:rowOrder >= 100 or @diffgr:id = "Holidays21"]/Name   (evaluates to "Thanksgiving")

In the next post we'll look at some common XPath functions.

XPath in soapUI Part 1: XPath Assertions and Namespaces

After a long hiatus for the American holidays, in response to numerous requests I'm going to look at using XPath in soapUI over the next two or three posts.  In this post we'll walk through creating a very basic XPath assertion and discuss namespaces, which almost always pop up but can be a bit tricky and not very intuitive if you're new to XPath.  For the sake of space and time, this may seem like a bit of a whirlwind introduction, but I'm hoping it will be more than enough to get you started.  For an in-depth look at XPath or to fill in the gaps, I recommend the tutorial at w3schools.com.

You can download a zipped sample project here with several request steps for which you can create and experiment with your own XPath assertions.  The service returns information about holidays in several countries; e.g., it returns a list of holidays in a given year, the date of a given holiday, etc.  Also, it doesn't use CDATA-- as I discussed in previous posts, services that make extensive use of CDATA require some extra scripting to get them to work with XPath.  Download the project, unzip it, and import it into your soapUI workspace (if you want to create your own project from scratch, the WSDL for this services is at http://www.holidaywebservice.com/Holidays/HolidayService.asmx?WSDL).

Let's walk through creating a simple XPath assertion.  Once you've imported the project and opened it in soapUI, run the GetHolidayDate test request in the GetHolidayDate test case; the response should look something like this:

GetHolidayDate Response XML
SoapUI's XPath assertions allow you to confirm that a specified value in your test request's response XML matches some expected value.  Let's create an assertion that verifies the request is returning the expected date-- in other words, that the value of the GetHolidayDateResult element is '2013-01-01T00:00:00'.  Open the test step editor and expand the Assertions panel, if necessary (click on the Assertions button at the bottom of the editor window).  Open the Add Assertion dialog; the XPath Match assertion is available in the Property Content group.

XPath Match in the Add Assertion dialog
After selecting the XPath Match assertion type, the XPath Match Configuration dialog is launched:

XPath Match Configuration dialog
Once in this dialog, click on the Declare button above the top panel-- soapUI scans the test response to try to identify any namespaces used and automatically creates corresponding declarations:

Namespace declarations automatically generated by soapUI
For those of you unfamiliar with namespaces (and those of you who are may want to skim the next few paragraphs), these provide a way to avoid naming conflicts in XML.  For example, you may have two web services that both return an element named "Addressee".  Associating each "Addressee" element with a different namespace ensures that each remains unique.  Namespaces are generally defined within XML tags using the following syntax:

xmlns[:prefix]="someNamespaceHere"

The colon and prefix are optional.  If the namespace is defined without specifying a prefix (e.g., xmlns = "http://www.someName.com"), it applies to the element for which it's defined and children of that element (assuming they don't have namespace prefixes or their own xmlns attribute defined in the same way).  If the namespace is defined with a prefix (e.g., xmlns:ns = "http://www.someOtherName.com"), XML nodes can be associated with that namespace by using its defined prefix and a colon (e.g., an element labelled ns:Element1 would be associated with the namespace "http://www.someOtherName.com").

Let's return to our example.  Look again at the GetHolidayDateResult element in the response above.  Its namespace ("http://www.27seconds.com/Holidays/") is specified as an attribute of its parent element, GetHolidayDateResponse.  Cross-checking this with the soapUI-generated declarations, we can see this namespace was declared for our XPath expression using the prefix "ns1".  We can now write our XPath expression using the correct namespace prefix.  Type the following in the XPath Match Configuration dialog below the namespace declarations:

//ns1:GetHolidayDateResult

The leading double-slashes signify that we want to find an instance of the GetHolidayDateResult element wherever it occurs in our XML tree.  Click on the "Select from current" button below the XPath Expression panel to evaluate the expression-- it should return the value "2013-01-01T00:00:00".  Save the assertion, giving it a meaningful name (so you know at a glance exactly what's passing or failing); in subsequent test runs, the assertion will be re-evaluated and passed or failed accordingly.

As I mentioned at the beginning of this post, namespaces can get a little tricky.  While soapUI will help you out by automatically generating namespace declarations, you're on your own when it comes to using those namespaces correctly in your XPath expression-- if you enter an incorrect namespace prefix (or forget to use one where one is needed), you'll simply get a message that a match can't be found.  In fact, if you see this behavior and you can't find any obvious errors (e.g., typos), a namespace prefix is frequently the culprit and might be the first thing you'll want to double-check.  Note also that soapUI's auto-declared prefix for a given namespace may not necessarily match the prefix defined in the response XML; in this case, you want to use soapUI's declared prefix.

Obviously, this is a very simple example; in the next post (which I promise won't be six weeks from now) we'll look at some more complex expressions.