Use array_fill() to simulate data fill for unit testing

M66 2025-06-05

In PHP development, unit testing is an important method of quality assurance. In order to effectively test the logic of a program, we often need to simulate a large amount of data input. The built-in function array_fill() of PHP can quickly generate a specified number of array elements, which is very suitable for simulating data fill and simplifying the preparation of unit tests.

What is array_fill()?

The array_fill() function is used to create an array containing a specified number and all elements are the same. The basic syntax is as follows:

 array_fill(int $start_index, int $count, mixed $value): array

$start_index : The starting index of the array.
$count : The number of elements to be filled.
$value : The value used to fill.

Let's give a simple example:

 $arr = array_fill(0, 5, 'test');
print_r($arr);

Output:

 Array
(
    [0] => test
    [1] => test
    [2] => test
    [3] => test
    [4] => test
)

Simulate data in unit tests

Suppose you need to test a function that processes user information, and you don't want to manually prepare a large amount of data every time, array_fill() can help you generate unified test data.

 function processUsers(array $users) {
    // Assume processing of user information，Return number of users
    return count($users);
}

// use array_fill generate 100 Simulated user data
$mockUsers = array_fill(0, 100, [
    'id' => 0,
    'name' => 'Test User',
    'email' => 'user@m66.net'
]);

echo processUsers($mockUsers); // Output 100

In the above example, 100 user data with a unified format are simulated to facilitate performance and logic testing of batch processing functions.

Customize fill objects and complex structures

For more complex data structures, you can also use array_fill() to form a basic array with anonymous functions or loops, and then adjust some data through traversal.

 $mockUsers = array_fill(0, 10, null);

foreach ($mockUsers as $index => &$user) {
    $user = [
        'id' => $index + 1,
        'name' => "User {$index}",
        'email' => "user{$index}@m66.net"
    ];
}
unset($user);

print_r($mockUsers);

This will keep each simulated data unique and closer to the real business scenario.

Conclusion

array_fill() is a concise and efficient array generation function in PHP, which can greatly simplify the data preparation of unit tests. Whether it is to uniformly fill simple values or to generate complex structures in combination with loops, it can help developers build test cases faster and improve test efficiency and code quality.

array_fill