change secret to required

README.md

@@ -22,7 +22,7 @@ composer require yasuaki640/cognito-srp-php
     $srpHelper = new CognitoSrp(
         'your client id',
         'your pool id',
-        'your client secret (if set)',
+        'your client secret (required)',
     );
 
     $result = $client->adminInitiateAuth([

src/CognitoSrp.php

@@ -46,7 +46,7 @@ class CognitoSrp
 
     private string $clientId;
 
-    private ?string $clientSecret;
+    private string $clientSecret;
 
     protected string $poolId;
 
@@ -58,7 +58,7 @@ class CognitoSrp
     public function __construct(
         string  $clientId,
         string  $poolId,
-        ?string $clientSecret = null
+        string $clientSecret
     ) {
         $this->N = new BigInteger(static::N_HEX, 16);
         $this->g = new BigInteger(static::G_HEX, 16);
@@ -301,10 +301,6 @@ public function SECRET_HASH(string $username): string
      */
     private function hashClientSecret(string $message): string
     {
-        if ($this->clientSecret === null) {
-            throw new \InvalidArgumentException('If the user pool has a client secret set, you must pass the `$clientSecret` argument to the constructor');
-        }
-
         $hash = hash_hmac(
             'sha256',
             $message,

tests/CognitoSrpTest.php

@@ -18,7 +18,8 @@ protected function setUp(): void
     {
         $this->srpHelper = new CognitoSrp(
             'dummy-client-id',
-            'dummy-pool-id'
+            'dummy-pool-id',
+            'dummy-client-secret'
         );
     }
 
@@ -31,14 +32,6 @@ public function test_calculate_SRP_A(): void
         $this->assertIsString($largeA);
     }
 
-    public function test_fail_if_SECRER_HASH_called_without_secret_hash(): void
-    {
-        $this->expectException(\InvalidArgumentException::class);
-        $this->expectExceptionMessage('If the user pool has a client secret set, you must pass the `$clientSecret` argument to the constructor');
-
-        $this->srpHelper->SECRET_HASH('dummy-username');
-    }
-
     public function test_SECRET_HASH_returns_hash_string(): void
     {
         $this->srpHelper = new CognitoSrp(