firefly-iii/app/tests/models/UserTest.php

<?php

class UserTest extends TestCase
{
    /**
     * Default preparation for each test
     */
    public function setUp()
    {
        parent::setUp();

        $this->prepareForTests();
    }

    /**
     * Migrate the database
     */
    private function prepareForTests()
    {
        Artisan::call('migrate');
    }

    /**
     * Username is required
     */
    public function testUsernameIsRequired()
    {
        // Create a new User
        $user = new User;
        $user->migrated = 0;
        $user->password = Str::random(60);

        // User should not save
        $this->assertFalse($user->isValid());

        // Save the errors
        $errors = $user->validator->messages()->all();
//        // There should be 1 error
        $this->assertCount(1, $errors);

//        // The username error should be set
        $this->assertEquals($errors[0], "The email field is required.");
    }

}