Framework: Unable to unit testing Many to Many Relationship with assertInstanceOf method

[mehti1367]

• Laravel Version: 5.8.19
• PHP Version: 7.3.5
• Database Driver & Version: libmysql - mysqlnd 5.0.12-dev - 20150407

Description:

Unable to testing Many to Many Relationship Assertion Failed :

Failed asserting that Illuminate\Database\Eloquent\Collection Object (...) is an instance of class "App\Tag".

Steps To Reproduce:

UnitThreadTest.php

namespace Tests\Unit;

use App\Tag;
use App\Thread;
use Tests\TestCase;
use Illuminate\Foundation\Testing\RefreshDatabase;

class ThreadTest extends TestCase
{
    use RefreshDatabase;

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

        $thread = factory(Thread::class)->create();

        $this->assertInstanceOf(Tag::class, $thread->tags);

    }

}

2019_06_01_114457_create_threads_table.php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateThreadsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('threads', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('title');
            $table->text('body');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('threads');
    }
}

2019_06_01_114508_create_tags_table.php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateTagsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('tags', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('tags');
    }
}

pivot table (2019_06_01_114720_create_tag_thread_table.php)

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateTagThreadTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('tag_thread', function (Blueprint $table) {
            $table->primary(['tag_id','thread_id']);
            $table->unsignedBigInteger('tag_id');
            $table->unsignedBigInteger('thread_id');

            $table->foreign('tag_id')->references('id')->on('tags')->onDelete('cascade');
            $table->foreign('thread_id')->references('id')->on('threads')->onDelete('cascade');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('tag_thread');
    }
}

Thread.php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Thread extends Model
{
    public function tags()
    {
        return $this->belongsToMany(Tag::class);
    }
}

Tag.php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Tag extends Model
{
    public function threads()
    {
        return $this->belongsToMany(Tag::class);
    }
}

ThreadFactory.php

/* @var $factory \Illuminate\Database\Eloquent\Factory */

use App\Thread;
use Faker\Generator as Faker;

$factory->define(Thread::class, function (Faker $faker) {
    return [
        'title' => $faker->sentence,
        'body'  => $faker->paragraph
    ];
});

TagFactory.php

/* @var $factory \Illuminate\Database\Eloquent\Factory */

use App\Thread;
use Faker\Generator as Faker;

$factory->define(Thread::class, function (Faker $faker) {
    return [
        'name' => $faker->word
    ];
});

Note that the code alone will work but its test not.

[staudenmeir]

Your test is incorrect. $thread->tags returns a collection of tags, not a single tag.

You can do something like this:

$this->assertInstanceOf(Tag::class, $thread->tags[0]);

[mehti1367]

@staudenmeir now:

ErrorException : Undefined offset: 0

[staudenmeir]

Your test doesn't create any tags, so the relationship result is empty.

[mehti1367]

I dont think so that was the problem , with Tag factory :

public function it_belongs_to_many_tags()
{
      factory(Tag::class)->create();
      $thread = factory(Thread::class)->create();

      $this->assertInstanceOf(Tag::class, $thread->tags[0]);

}

same error:

ErrorException : Undefined offset: 0

[staudenmeir]

You also have to create records in the pivot table, that's what the relationship is all about.

[mehti1367]

thanks i forgot about the pivot table, here is the solution maybe helps somebody :

public function it_belongs_to_many_tags()
{
    $tag = factory(Tag::class)->create();
    $thread = factory(Thread::class)->create();

    DB::table('tag_thread')->insert([
       'tag_id' => $tag->id,
       'thread_id' => $thread->id
    ]);

    $this->assertInstanceOf(Tag::class, $thread->tags[0]);

}