Add tests for realm case sensitivity in AuthStore

As per RFC 1945 (section 11) and RFC 2617, the realm value is case sensitive.
This commit adds tests for realm case sensitivity in
Mechanize::HTTP::AuthStore.

test/test_mechanize_http_auth_store.rb

@@ -57,6 +57,20 @@ def test_add_auth_realm
     assert_equal expected, @store.auth_accounts
   end
 
+  def test_add_auth_realm_case
+    @store.add_auth @uri, 'user1', 'pass', 'realm'
+    @store.add_auth @uri, 'user2', 'pass', 'Realm'
+
+    expected = {
+      @uri => {
+        'realm' => ['user1', 'pass', nil],
+        'Realm' => ['user2', 'pass', nil],
+      }
+    }
+
+    assert_equal expected, @store.auth_accounts
+  end
+
   def test_add_auth_string
     @store.add_auth "#{@uri}/path", 'user', 'pass'
 
@@ -143,6 +157,14 @@ def test_credentials_for_realm
     assert_equal ['user1', 'pass', nil], @store.credentials_for(@uri, 'other')
   end
 
+  def test_credentials_for_realm_case
+    @store.add_auth @uri, 'user1', 'pass', 'realm'
+    @store.add_auth @uri, 'user2', 'pass', 'Realm'
+
+    assert_equal ['user1', 'pass', nil], @store.credentials_for(@uri, 'realm')
+    assert_equal ['user2', 'pass', nil], @store.credentials_for(@uri, 'Realm')
+  end
+
   def test_credentials_for_path
     @store.add_auth @uri, 'user', 'pass', 'realm'
 
@@ -183,6 +205,21 @@ def test_remove_auth_realm
     assert_equal expected, @store.auth_accounts
   end
 
+  def test_remove_auth_realm_case
+    @store.add_auth @uri, 'user1', 'pass', 'realm'
+    @store.add_auth @uri, 'user2', 'pass', 'Realm'
+
+    @store.remove_auth @uri, 'Realm'
+
+    expected = {
+      @uri => {
+        'realm' => ['user1', 'pass', nil]
+      }
+    }
+
+    assert_equal expected, @store.auth_accounts
+  end
+
   def test_remove_auth_string
     @store.add_auth @uri, 'user1', 'pass'