Test failing with Session is missing expected key [errors]

I have this test that checks that the active field is either 0 or 1:

it('requires valid data', function ($active) {
    // Arrange
    Belt::factory()->create([
        'min_xp' => 0,
    ]);

    $character = Character::factory()->create();

    $this->actingAs($character->user)
        ->put(route('characters.update', ['character' => $character]), ['active' => $active])
        ->assertInvalid('active');
})->with([
    null,
    1,
    1.5,
    str_repeat('a', 2),
]);

However it is failing with Session is missing expected key [errors].. Here is my Vue:

<template>
    <AppLayout title="My Characters">
            <div class="grid row mt-5">
                <div class="col-span-6 m-auto">
                    <div class="block max-w-sm p-6 bg-white border border-gray-200 rounded-lg shadow hover:bg-gray-100 dark:bg-gray-800 dark:border-gray-700 dark:hover:bg-gray-700">
                        <h1 class="text-center mb-3">
                            <i aria-hidden="true"></i>  Characters
                        </h1>
                        <div v-if="characters.length === 0">
                            <p>You have no characters, why not create a new character?</p>
                            <Link :href="route('characters.create')" class="inline-block border border-blue-500 rounded py-1 px-3 bg-blue-500 text-white" role="link" title="Create a new character">Create a new character</Link>
                        </div>
                        <table v-else class="table-auto border-spacing-2 text-center">
                            <thead>
                            <tr>
                                <th scope="col">Name</th>
                                <th scope="col">Active</th>
                                <th scope="col">Options</th>
                            </tr>
                            </thead>
                            <tbody>
                            <tr v-for="character in characters" :key="character.id">
                                <th scope="row">{{ character.name }}</th>
                                <td><span v-if="character.active">X</span></td>
                                <td>
                                    <Link :href="route('characters.show', {character: character})" class="text-sm text-gray-600 hover:text-gray-900 dark:text-gray-400 dark:hover:text-white focus:outline focus:outline-2 focus:rounded-sm focus:outline-red-500">Show</Link>&nbsp;
                                    <Link v-if="!character.active" @click="switchCharacter(character.id)" class="text-sm text-gray-600 hover:text-gray-900 dark:text-gray-400 dark:hover:text-white focus:outline focus:outline-2 focus:rounded-sm focus:outline-red-500">Make active</Link></td>
                            </tr>
                            </tbody>
                        </table>
                    </div>
                </div>
            </div>
    </AppLayout>
</template>
<script setup>
import AppLayout from "@/Layouts/AppLayout.vue";
import {Link} from "@inertiajs/vue3";

defineProps(['characters']);

const switchCharacter = (characterId) => {
    fetch(`/characters/${characterId}`, {
        method: 'PUT',
        headers: {
            'Content-Type': 'application/json',
            'X-CSRF-TOKEN': document.querySelector('meta[name="csrf-token"]').getAttribute('content')
        },
        body: JSON.stringify({})
    })
        .then(response => {
            console.log(response); // Log the response for debugging
            if (response.ok) {
                // Handle success, maybe update the UI
                alert('Character switched successfully!');
                window.location.reload(); // Reload the page to reflect changes
            } else {
                // Handle error
                alert('Failed to switch character.');
            }
        })
        .catch(error => {
            console.error('Error:', error);
            alert('Failed to switch character.');
        });
}
</script>

And here is my route action:

    /**
     * Update the specified resource in storage.
     */
    public function update(Request $request, Character $character)
    {
        // if the character is already the active
        if ($character->active) {

            // then redirect to the characters index
            return redirect('characters');
        }

        // get the player's active character if any
        $activecharacter = Character::where('user_id', auth()->user()->id)
            ->where('active', 1)
            ->first(['id', 'active']);

        // if the play has an active character
        if ($activecharacter) {

            // mark the previous character as not active
            $activecharacter->update(['active' => 0]);
        }

        // set the selected character as the active one
        $character->update(['active' => 1]);

        // then redirect to the characters index
        return response(200);
    }

I am using this as my base. It was suggested here that I add validation to my route action. However as per my response to the ai:

@LaryAI Unfortunately, the issue persists. If I add validation the route no longer works. Additionally, there is no actual input to validate because there is no actual input required by the user besides clicking on a link/button which already has the character id baked in.

Any ideas?