Improve tests

Dapper.Tests/Tests.Async.cs

@@ -30,14 +30,14 @@ public async Task TestBasicStringUsageQueryFirstAsync()
         [Fact]
         public async Task TestBasicStringUsageQueryFirstOrDefaultAsync()
         {
-            var str = await connection.QueryFirstOrDefaultAsync<string>(new CommandDefinition("select null as [Value]"));
+            var str = await connection.QueryFirstOrDefaultAsync<string>(new CommandDefinition("select null as [Value] union all select @txt", new {txt = "def"}));
             str.IsNull();
         }
 
         [Fact]
         public async Task TestBasicStringUsageQuerySingleAsync()
         {
-            var str = await connection.QuerySingleAsync<string>(new CommandDefinition("select 'abc' as [Value] union all select @txt", new {txt = "def"}));
+            var str = await connection.QuerySingleAsync<string>(new CommandDefinition("select 'abc' as [Value]"));
             str.IsEqualTo("abc");
         }