Why are specific asserts better than generic asserts, in PHPUnit?

Question

Please excuse my ignorance; I am still new to the unit testing realm.

Can someone explain why..

$this->assertGreaterThan( 2, $result );

..is better than..

$this->assertTrue( $result > 2 );

..(and likewise, all the other specific assert methods)?

Thanks!

Answer 1

If you showed your mum/dad/uncle those, the assertGreaterThan is far more intuitive. Plus the failed message for the isGreaterThan will be much better

"1 was not greater than 2"

or

"false was not true"

Which one is more expressive?

Answer 2

Actually, the best method provides better readability and better failure messages: use the PHPUnit function-based assertions or Hamcrest library.

assertThat(count($users), greaterThan(2));

>> Expected: greater than 2
>>      but: was 1

or

assertThat($users, arrayWithSize(greaterThan(2)));

>> Expected: array with size greater than 2
>>      but: was array with size 1

You can always provide a readable error message with any assertion by adding a string as the first parameter to the assertion methods or Hamcrest's assertThat function or the third parameter to PHPUnit's assertThat function:

self::assertTrue('At least one user found', !empty($users));

>> At least one user found
>> Expected: true
>>      but: false

or

assertThat('At least one user found', !empty($users), is(true));

>> At least one user found
>> Expected: true
>>      but: false