PHPUnit testing a method that depends on another method

Question

This is my Database class and I want to test rowCount method returning correct value:

namespace MyProject\Database;

class Database {

    // database connection
    private $conn = NULL;

    // holds query statement object
    private $statement = NULL;

    public function __construct(\PDO $conn) {

        $this->conn = $conn;
    }

    public function query(string $query, array $parameters=[]) : bool {

        $this->statement = $this->conn->prepare($query);
        return $this->statement->execute($parameters);
    }

    public function rowCount() : int {

        return $this->statement->rowCount();
    }
}

I wrote this unit test at first to test rowCount method but as you can see I also used the query method to run the query:

class DatabaseTest extends \PHPUnit\Framework\TestCase {

    /** @test */
    public function rowCountReturnsCorrectNumber() {

        $pdo = new \PDO('sqlite::memory:');

        $db = new \MyProject\Database\Database($pdo);

        // we are not testing query method here but we use it to run the query
        $db->query("CREATE TABLE test (id INT UNSIGNED PRIMARY KEY)");
        $db->query("INSERT INTO test (id) VALUES (1),(2)");

        $this->assertEquals(2,$db->rowCount());
    }
}

I thought query method can have errors at the future so why should I depend on that. I wrote this to avoid it:

class DatabaseTest extends \PHPUnit\Framework\TestCase {

    /** @test */
    public function rowCountReturnsCorrectNumber() {

        $pdo = new \PDO('sqlite::memory:');

        $db = new \MyProject\Database\Database($pdo);

        $s = $pdo->prepare("CREATE TABLE test (id INT UNSIGNED PRIMARY KEY)");
        $s->execute();
        $s2 = $pdo->prepare("INSERT INTO test (id) VALUES (1),(2)");
        $s2->execute();

        // here I set statement (private property)
        $reflection = new \ReflectionClass($db);
        $property = $reflection->getProperty('statement');
        $property->setAccessible(true);
        $property->setValue($db, $s2);

        $this->assertEquals(2,$db->rowCount());
    }
}

Now my question is that: I think this is not a good approach while statement is a private property. On the 2nd test I can only test rowCount method and nothing else but I used private property and I think it can make maintenance so hard in the future. Which one is correct? Should I test it in another way?

Jeto · Accepted Answer · 2020-01-25 20:41:59Z

1

You may use @depends which allows you to explicitly declare dependencies between your tests:

class DatabaseTest extends \PHPUnit\Framework\TestCase
{
  /**
   * @test
   */
  public function yourQueryTest()
  {
    // ...
  }


  /**
   * @test
   * @depends yourQueryTest
   */
  public function rowCountReturnsCorrectNumber()
  {
    // ...
  }
}

where yourQueryTest is a test for \MyProject\Database\Database#query.

answered Jan 25, 2020 at 20:41

Jeto

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