Laravel 6 Unit Testing Responses

I am using Token based operations. The request for the Edit operation in Project works well in Postman.

public function update(Request $request, $id)
    {
        $project = Project::find($id);
        $project->project_name = request('project_name');
        $project->project_description = request('project_description');
        $project->save();
        return response()->json([
            'message' =>  "Project Updated Successfully",
            'updatedId' => $project->id
            ], 200);
    }

But in Unit Testing Not getting Proper Responses

 public function testBasicExample()
    {
        $response = $this->withHeaders([
            'Accept' => 'application/json',
            'Authorization' => 'Bearer eyJ0eXAiOiJKV1QiLCJhbGciOi......'
        ])->json('POST', '/api/updateProject/1',
                ['project_name' => 'Sally'],
                ['project_description' => 'testing the api']
                );

                $response->assertStatus(200);
                $response->assertJson(['status' => true]);
    }

Error Shows

PS D:\XMAPP\htdocs\minidmsapi> ./vendor/bin/phpunit
PHPUnit 8.4.1 by Sebastian Bergmann and contributors.

..F.                                                                4 / 4 (100%)

Time: 597 ms, Memory: 18.00 MB

There was 1 failure:

1) Modules\Projects\Tests\Unit\ProjectTest::testBasicExample
Expected status code 200 but received 500.
Failed asserting that false is true.

D:\XMAPP\htdocs\minidmsapi\vendor\laravel\framework\src\Illuminate\Foundation\Testing\TestResponse.php:166
D:\XMAPP\htdocs\minidmsapi\Modules\Projects\Tests\Unit\ProjectTest.php:35

FAILURES!
Tests: 4, Assertions: 4, Failures: 1.

Why Unit Testing having Error Response 500 and some times its 401 ?

Kindly anyone, please explain to me What is the actual error in unit testing and solution for that.