Author image Tony Byrne
and 1 contributors


TypeAdapters are responsible for two tasks:

1. Converting the text contained in a cell into a "value", e.g. a string or a float. ("parse" method)

2. Checking for equality of that value against the computed value delivered by the fixture. ("equals" method)

Without specifying a TypeAdatper the GenericTypeAdapter will be usesd. This TypeAdapter performs no parsing, the cell text will be just passed to the subsequent stages. The "check"-part - at present - tries to figure out what kind the parameters (cell text and fixture value) are of, in order to make the right check - boolean, numerical or string.

Parameters are treated as booleans if they contain one of the literal strings "true" or "false".

Parameters are treated as numbers if they match some simple rules. The numerical equality check is then delegated to the ScientificDouble (domain-) type.

If the parameters are blessed objects, a call to $obj->equals is tried. The last possibility - and therefore the default behavior is the string "eq" check.

So if all this is available, what are specific TypeAdapters good for?

There are following reasons:

Ensuring the right check-type (boolean, numerical, string or other)

Given the two values '007' and '7', they are numerically equal, by contrast, they are not string equal. A specific TypeAdapter gives you the opportunity to define the right check.

Different representation of a value

Either the underlying domain type stores the value in a human-unreadable form, or there are different valid forms and the value stored in the underlying domain type is not in canonical form. An example for the first case is "duration". A human readable form might be "HH:MM:SS" or "MMM:SS", the domain type holds the value as number of seconds ("SSSSS"). In this case you need a specific parse-part, but no specific check part (as number of seconds can be compared numerically). The second case is used if a value entered by an user should be printed out in the very same form as entered. If this is true, the "equals"-part has to convert both values to canonical form and check them appropriately.

The domain type in the system under test is not a scalar

This is the case e.g. for GenericArrayAdapter. If a blessed reference is needed, you'll propably call a object->new() in the parse method. You also have to ensure, that check makes the right job, unless:

- Your domain type implements an equals() method, or

- Your domain type overloads the stringify ('""' => 'as_string') or eq operator

The cell text cannot be converted one-to-one to a single value

E.g. a date given in the form "YYY-MM-DD" may represent one or 86400 (24 * 60 * 60) values of a unix-time type (which holds a number of seconds since 1970-01-01), depending on your case. You have to implement both parse() and check() on your own.

Valid values of the domain type are restricted.

This is the case if the domain type is an enum (e.g. rating of a bond) or if the range is restricted - e.g a discount in percent which is valid only in the range 0 - 100.

If the domain type is implemented using a scalar value, the validity check must be done in the specific TypeAdapter. If the domain type is a blessed objects, this task might be delegated by the TypeAdapter to the domain type object.

Domain Type is a foreign key

This case occurs when the system under test operates on data comming from a relational database.

important: The following applies, only if your code does not interact with a database during the test!!!

Imagine a simple 1:n relation: person : hours_worked. The code to test contains a business logic which summs the entries in hours_worked per person or per person and some other criteria. Input to this business logic is a set of hours_worked entries. Output is a set of payroll_items. There is also a 1:n relation between person and payroll_items. So for the business logic, no attributes of person are needed.

Provided that the foreign key is numerical, a number could be written into the appropriate cells of the fit-document. This is simple, but you'd propably loose the willingness of your target audience in terms of writing further fit-documents.

A better solution is provided by a TypeAdapter which dynamically assigns a number (key) to a string (wrapped value) in a consistent way. All you need is an static hash and a static number generator. A fit-document contains a column "person name", this is bound to a specific TypeAdapter. Every parse(column text) checks if the column text has already been assigned a key, if not a new one will be generated. If a key has been assigned, it gets stored in the hash.

The first usage of a name generates a key, this is completely ok, as the system under test should rely on already known foreign keys. (If the code under test generates new foreign keys, it must generate new primary keys too. Then you need a different test for it!)