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Hamcrest - make your test assertion more declarative

shaikhul profile image Shaikhul Islam ・1 min read

Hamcrest framework was first introduced in Java world, later implemented in other languages (ex. PHP, Python, Ruby) with some exceptions depending on language scopes. It provides a wide range of matcher objects which make test assertion more meaningful and easier to understand.

I am going to use Hamcrest's PHP implementation.

Here is a starter example.

Installation

Hamcrest-php can be installed using composer

// first thing first, install hamcrest-php and include it, your vendor location may vary.

require __DIR__ . '/vendor/autoload.php';
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Quick use case - assertThat

Here is a simple example of assertThat matcher.

$result = true;
$expected = true;

assertThat($result, equalTo($expected));
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Give a nice optional description

You can give it a nice description about the assertion.

assertThat("Result should be true", $result, equalTo($expected));
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Add a decorator/sugar - is

Hamcrest also provides is decorator/sugar to make it super declarative!

assertThat("Result should be true", $result, is(equalTo($expected)));
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Asserting negation - not

Sometimes we need to test negativity, hamcrest cover this with not matcher.

$expected = true;
assertThat("Result should not be false", $result, is(not(equalTo($expected))));
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When it fails the assertion it shows error message like this

Hamcrest\AssertionError with message 'Result should be true
Expected: <false>
     but: was <true>'
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Feel free to checkout other matchers or hamcrest in other supported languages!

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