Unit testing a function containing DateTime("now")

Question

I have a function similar to this:

public function getSomeInfo($id){
    $date_start=new DateTime();
    $day_of_week=$date_start->format("N");
    $date_start=$date_start->sub(new DateInterval("P".$day_of_week."D"));
    $date_end=new $date_start;
    $date_end=$date_end->add(new DateInterval("P5D"));
    $date_start=$date_start->format("Y-m-d");
    $date_end=$date_end->format("Y-m-d");
    $sql="SELECT * FROM `table`  
            WHERE `table`.`id`=$id
            AND `session`.`date`>'$date_start'
            AND `session`.`date`<='$date_end'";
    $this->db->query($sql);
}

It returns a dataset for this current week, basically selects records from a table with a date between last Monday and This Sunday.

I want to be able to unit test this but I don't know how to do this when it is initiating a DateTime constructor. which will be for the current week but actually for testing purposes I only want one week of data in the testing dataset so really I want the test DateTime to be the same date every time.

Basically how can I set DateTime("now") to the same mock date everytime. I am using PHP, Codeigniter and PHPUnit/CIUnit (Implied in tags).

STLMikey · Accepted Answer · 2014-02-25 19:53:53Z

6

You could instead pass in the $date_start variable to the function, and when you call it in your test it would be the same every time ie

function testMymethod(){
   $date_start = new DateTime('2011-01-01');
   $class->getSomeInfo($id, $date_start);
   //assertions
}

And your method signiture would change to:

    class myclass {
      public function getSomeInfo($id, $date_start = new DateTime()){...}
    }

answered Feb 25, 2014 at 19:53

STLMikey

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2 Comments

EdL Over a year ago

Ah thanks, An example is worth a thousand words! An also this gives me the advantage of being able to use the same function for other weeks as well :)

maxime Over a year ago

I know it's a PHP limitation, but we're writing less explicit code just because PHP unit doesn't allows to mock global classes. A system like jest.mock on JS would be a way better solution, to be able to change the behavior of some modules for the tests without impacting the code readability.

gontrollez · Accepted Answer · 2014-02-25 19:54:24Z

6

There are (at least) 2 ways for this:

Delegate the action of getting the current time into another class. Have a TimeProvider or similar class passed to the method, as an external dependency, or by using a ServiceContainer or whatever way you like, and in the test use a mock or even a TimeProvider subclass that behaves the way you want.
Get the current time using a protected method and mock it (by creating a partial mock) of the subject under test.

I usually prefer the first way.

answered Feb 25, 2014 at 19:54

gontrollez

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