Unit Testing Dapper with Inline Queries

Question

I know there are several question similar to mine.

• Dapper: Unit Testing SQL Queries
• Testing Dapper Queries

butI don\'t think both of above

Answer 1

I adapted what @Mikhail did because I had issues when adding the OrmLite packages.

internal class InMemoryDatabase
{
    private readonly IDbConnection _connection;

    public InMemoryDatabase()
    {
        _connection = new SQLiteConnection("Data Source=:memory:");
    }

    public IDbConnection OpenConnection()
    {
        if (_connection.State != ConnectionState.Open)
            _connection.Open();
        return _connection;
    }

    public void Insert(string tableName, IEnumerable items)
    {
        var con = OpenConnection();

        con.CreateTableIfNotExists(tableName);
        con.InsertAll(tableName, items);
    }
}

I've created a DbColumnAttribute so we can specify a specific column name for a classes property.

public sealed class DbColumnAttribute : Attribute
{
    public string Name { get; set; }

    public DbColumnAttribute(string name)
    {
        Name = name;
    }
}

I added some IDbConnection extensions for the CreateTableIfNotExists and InsertAll methods.

This is very rough so I've not mapped types correctly

internal static class DbConnectionExtensions
{
    public static void CreateTableIfNotExists(this IDbConnection connection, string tableName)
    {
        var columns = GetColumnsForType();
        var fields = string.Join(", ", columns.Select(x => $"[{x.Item1}] TEXT"));
        var sql = $"CREATE TABLE IF NOT EXISTS [{tableName}] ({fields})";

        ExecuteNonQuery(sql, connection);
    }

    public static void Insert(this IDbConnection connection, string tableName, T item)
    {
        var properties = typeof(T)
            .GetProperties(BindingFlags.Public | BindingFlags.Instance)
            .ToDictionary(x => x.Name, y => y.GetValue(item, null));
        var fields = string.Join(", ", properties.Select(x => $"[{x.Key}]"));
        var values = string.Join(", ", properties.Select(x => EnsureSqlSafe(x.Value)));
        var sql = $"INSERT INTO [{tableName}] ({fields}) VALUES ({values})";

        ExecuteNonQuery(sql, connection);
    }

    public static void InsertAll(this IDbConnection connection, string tableName, IEnumerable items)
    {
        foreach (var item in items)
            Insert(connection, tableName, item);
    }

    private static IEnumerable> GetColumnsForType()
    {
        return from pinfo in typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance)
            let attribute = pinfo.GetCustomAttribute()
            let columnName = attribute?.Name ?? pinfo.Name
            select new Tuple(columnName, pinfo.PropertyType);
    }

    private static void ExecuteNonQuery(string commandText, IDbConnection connection)
    {
        using (var com = connection.CreateCommand())
        {
            com.CommandText = commandText;
            com.ExecuteNonQuery();
        }
    }

    private static string EnsureSqlSafe(object value)
    {
        return IsNumber(value)
            ? $"{value}"
            : $"'{value}'";
    }

    private static bool IsNumber(object value)
    {
        var s = value as string ?? "";

        // Make sure strings with padded 0's are not passed to the TryParse method.
        if (s.Length > 1 && s.StartsWith("0"))
            return false;

        return long.TryParse(s, out long l);
    }
}

You can still use it the same way as @Mikhail mentions in Step 3.