Comparators
The comparator is a module which is responsible for consuming data and comparing it to the pattern or against a defined set of rules.
Each comparator presented in the section below consists of the following three elements:
- consumed resource type,
- module name (comparator),
- parameters.
This is a name of the resource type consumed by the defined comparator. This is always a name of the tag definition for the comparator.
This name tells the system which resource type should be consumed by the defined comparator. When no comparator in the system can consume the defined resource type, a system exception will occur and the test will not be performed. This solution enables to add new features to the system with no system downtime (just by installing a new feature bundle).
Each comparator can consume only one resource type.
This is a special parameter, a unique name for the comparator type treated as the interpretation of a given resource type. The system will recognize which implementation of the comparator should be called by this name. This parameter is required for each comparator but the system will assume a default comparator for each resource type when no comparator property is defined.
- cookie -> CookieComparator,
- js errors -> JSErrorsComparator,
- screen -> LayoutComparator,
- source -> SourceComparator,
- status-codes -> StatusCodesComparator.
Sample usage can be found in the system for the source comparison where two comparators exist: W3C HTML5 Comparator and Source Comparator. The example below shows its sample usage:
...
<collect>
<open/>
<source/>
</collect>
<compare>
<source comparator="source"/>
<source comparator="w3c-html5"/>
</compare>
...When the test defined as shown above is executed, collection of a page source is performed only once but the result of this collection is used twice during the comparison phase. First by Source Comparator and then by W3C HTML5 Comparator.
This is a set of key-value pairs allowing the user to pass some configuration and information to the comparator. Parameters for comparators can be divided into the following two groups:
- mandatory - parameters which comparison will be not possible without,
- optional - passing this parameter is not obligatory, usually this is the extension of some comparator functionality.
There exists the special comparator property collectorName which is connected to the collector name property. By using the collectorName property combined with the collector name property the user can control which comparator instance compares results collected by a particular collector. See examples below:
...
<collect>
<open/>
<sleep duration="1000"/>
<resolution width="1280" height="1024" name="desktop"/>
<screen name="desktop"/>
<resolution width="768" height="1024" name="tablet"/>
<screen name="tablet"/>
<resolution width="320" height="480" name="mobile"/>
<screen name="mobile"/>
</collect>
<compare>
<screen collectorName="desktop"/>
<screen collectorName="mobile"/>
<screen collectorName="tablet"/>
</compare>
...The configuration above will trigger three screens collections (desktop, tablet and mobile) and two comparisons (mobile and tablet). The screenshot taken for desktop will not be compared.
...
<collect>
<open/>
<sleep duration="1000"/>
<resolution width="1280" height="1024" name="desktop"/>
<screen name="desktop"/>
<resolution width="768" height="1024" name="tablet"/>
<screen name="tablet"/>
<resolution width="320" height="480" name="mobile"/>
<screen name="mobile"/>
</collect>
<compare>
<screen/>
</compare>
...The configuration above will trigger three screens collections (desktop, tablet and mobile) and three comparisons (desktop, table, mobile).
...
<collect>
<open/>
<sleep duration="1000"/>
<resolution width="1280" height="1024" name="desktop"/>
<screen name="desktop"/>
<resolution width="768" height="1024" name="tablet"/>
<screen name="tablet"/>
<resolution width="320" height="480" name="mobile"/>
<screen name="mobile"/>
</collect>
<compare>
<screen/>
<screen collectorName="tablet"/>
</compare>
...The configuration above will trigger three screens collections (desktop, tablet and mobile) and four comparisons (desktop, tablet, mobile and one additional for the tablet).
The following picture depicts definitions described earlier:
where:
- Consumed resource type,
- Special property: collectorName,
- Special property: comparator,
- Module name (comparator).