Various fixes

lib/github/kv.rb

@@ -267,7 +267,9 @@ module GitHub
     def increment(key, amount: 1, expires: nil)
       validate_key(key)
       validate_amount(amount) if amount
-      validate_expires(expires) if expries
+      validate_expires(expires) if expires
+
+      expires ||= GitHub::SQL::NULL
 
       # This query uses a few MySQL "hacks" to ensure that the incrementing
       # is done atomically and the value is returned. The first trick is done
@@ -420,10 +422,10 @@ module GitHub
     #    # => #<Result value: [2018-04-23 11:34:54 +0200, nil]>
     #
     def mttl(keys)
-      validate_keys(key)
+      validate_key_array(keys)
 
       Result.new {
-        kvs = GitHub::SQL.value(<<-SQL, :keys => keys, :now => now, :connection => connection).to_h
+        kvs = GitHub::SQL.results(<<-SQL, :keys => keys, :now => now, :connection => connection).to_h
           SELECT expires_at FROM key_values
           WHERE `key` in :keys AND (expires_at IS NULL OR expires_at > :now)
         SQL

test/github/kv_test.rb

@@ -255,6 +255,19 @@ class GitHub::KVTest < Minitest::Test
     assert_nil @kv.ttl("foo-ttl").value!
   end
 
+  def test_mttl
+    assert_equal [nil, nil], @kv.mttl(["foo-ttl", "bar-ttl"]).value!
+
+    # the Time.at dance is necessary because MySQL does not support sub-second
+    # precision in DATETIME values
+    expires = Time.at(1.hour.from_now.to_i).utc
+    @kv.set("foo-ttl", "bar", expires: expires)
+
+    puts @kv.mttl(["foo-ttl", "bar-ttl"]).value!
+
+    assert_equal [expires, nil], @kv.mttl(["foo-ttl", "bar-ttl"]).value!
+  end
+
   def test_type_checks_key
     assert_raises TypeError do
       @kv.get(0)