Changes made during pair review with @tarrow

* Allow `accepted_at` attribute to be mass-assigned. Preventing this doesn't provide that much extra security but does create some slightly confusing behaviour. Potential follow up to make the model set `accepted_at` to `CarbonImmutable::now()` if missing or `null`.
* Use `$table->dateTime('accepted_at')` instead of `->timestamp()` in db migration - see comment in the code for rational.
* Replaced `testAcceptedAtIgnoresMassAssignment()` with `testCreateFailsIfAcceptedAtIsMissing()` and `testCreateFailsIfAcceptedAtIsNull()` now that `ccepted_at` is mass-assignable.
* Add unique constraint on `user_id` and `policy_id` in the `create_policy_acceptances_table` migration and added a test.
* Add comment as to why casting to `immutable_datetime` in the models.

Author: outdooracorn

app/Policy.php

@@ -42,9 +42,10 @@ class Policy extends Model {
 
     protected function casts(): array {
         return [
-            // cast `active_from` to a CarbonImmutable instance rather than a string
+            // cast `active_from` to a `CarbonImmutable` instance rather than a string
             'active_from' => 'immutable_date',
 
+            // cast to `CarbonImmutable` until we default to using `CarbonImmutable` globally in T430656
             'created_at' => 'immutable_datetime',
             'updated_at' => 'immutable_datetime',
         ];

app/PolicyAcceptance.php

@@ -35,11 +35,6 @@ class PolicyAcceptance extends Model {
     protected $fillable = [
         'user_id',
         'policy_id',
-    ];
-
-    protected $guarded = [
-        // Don't allow `accepted_at` to be mass assigned.
-        // Most of the time this will be set to the current timestamp by the database.
         'accepted_at',
     ];
 
@@ -48,6 +43,7 @@ protected function casts(): array {
             // cast `accepted_at` to a `CarbonImmutable` instance rather than a string
             'accepted_at' => 'immutable_datetime',
 
+            // cast to `CarbonImmutable` until we default to using `CarbonImmutable` globally in T430656
             'created_at' => 'immutable_datetime',
             'updated_at' => 'immutable_datetime',
         ];

database/migrations/2026_06_22_083910_create_policy_acceptances_table.php

@@ -21,10 +21,15 @@ public function up(): void {
             // Using a separate `accepted_at` column rather than renaming the default `created_at` column because:
             //   * it reduces confusion by remaining consistent with other tables that use these default columns
             //   * `accepted_at` will be before `created_at` when backfilling the terms-of-use acceptances
-            $table->timestamp('accepted_at')->useCurrent();
+            // Using a DATETIME field as MariaDB has odd behavior around TIMESTAMPs and default values
+            // `accepted_at` can be NOT NULL if we use a DATETIME which provides us with more data safety
+            $table->dateTime('accepted_at');
 
             // Use Eloquent built in to create nullable `created_at` and `updated_at` timestamp fields
             $table->timestamps();
+
+            // Prevent a user from accepting the same policy twice
+            $table->unique(['user_id', 'policy_id']);
         });
     }
 

tests/PolicyAcceptanceTest.php

@@ -7,6 +7,7 @@
 use App\User;
 use Carbon\CarbonImmutable;
 use Illuminate\Foundation\Testing\RefreshDatabase;
+use RuntimeException;
 
 class PolicyAcceptanceTest extends TestCase {
     use RefreshDatabase;
@@ -33,6 +34,7 @@ public function testCreatesAndSavesSuccessfully(): void {
             [
                 'user_id' => $this->userId,
                 'policy_id' => $this->policyId,
+                'accepted_at' => CarbonImmutable::now(),
             ]
         );
         $policyAcceptance->save();
@@ -47,14 +49,34 @@ public function testCreatesAndSavesSuccessfully(): void {
         $this->assertInstanceOf(CarbonImmutable::class, $policyAcceptance->accepted_at);
     }
 
-    public function testAcceptedAtIgnoresMassAssignment(): void {
-        $policyAcceptance = PolicyAcceptance::create(
-            [
-                'user_id' => $this->userId,
-                'policy_id' => $this->policyId,
-                'accepted_at' => CarbonImmutable::createFromDate(2026, 1, 1),
-            ]
-        );
-        $this->assertNull($policyAcceptance->accepted_at);
+    public function testCreateFailsIfAcceptedAtIsMissing() {
+        $this->expectException(RuntimeException::class);
+        PolicyAcceptance::create([
+            'user_id' => $this->userId,
+            'policy_id' => $this->policyId,
+        ]);
+    }
+
+    public function testCreateFailsIfAcceptedAtIsNull() {
+        $this->expectException(RuntimeException::class);
+        PolicyAcceptance::create([
+            'user_id' => $this->userId,
+            'policy_id' => $this->policyId,
+            'accepted_at' => null,
+        ]);
+    }
+
+    public function testUserAcceptingSamePolicyTwiceFails() {
+        PolicyAcceptance::create([
+            'user_id' => $this->userId,
+            'policy_id' => $this->policyId,
+            'accepted_at' => CarbonImmutable::now()->subSeconds(2),
+        ]);
+        $this->expectException(RuntimeException::class);
+        PolicyAcceptance::create([
+            'user_id' => $this->userId,
+            'policy_id' => $this->policyId,
+            'accepted_at' => CarbonImmutable::now(),
+        ]);
     }
 }