除非我誤解了,否則您將切換實施EcaseReferralCases與另一個IQueryable
,可能是一個LINQ To Objects可查詢源。
最可靠的方法可能是使用表達式訪問者用您自己的L2Objects兼容函數替換對EntityFunctions
的調用。
這是我實現:
using System;
using System.Data.Objects;
using System.Linq;
using System.Linq.Expressions;
static class EntityFunctionsFake
{
public static DateTime? AddDays(DateTime? original, int? numberOfDays)
{
if (!original.HasValue || !numberOfDays.HasValue)
{
return null;
}
return original.Value.AddDays(numberOfDays.Value);
}
}
public class EntityFunctionsFakerVisitor : ExpressionVisitor
{
protected override Expression VisitMethodCall(MethodCallExpression node)
{
if (node.Method.DeclaringType == typeof(EntityFunctions))
{
var visitedArguments = Visit(node.Arguments).ToArray();
return Expression.Call(typeof(EntityFunctionsFake), node.Method.Name, node.Method.GetGenericArguments(), visitedArguments);
}
return base.VisitMethodCall(node);
}
}
class VisitedQueryProvider<TVisitor> : IQueryProvider
where TVisitor : ExpressionVisitor, new()
{
private readonly IQueryProvider _underlyingQueryProvider;
public VisitedQueryProvider(IQueryProvider underlyingQueryProvider)
{
if (underlyingQueryProvider == null) throw new ArgumentNullException();
_underlyingQueryProvider = underlyingQueryProvider;
}
private static Expression Visit(Expression expression)
{
return new TVisitor().Visit(expression);
}
public IQueryable<TElement> CreateQuery<TElement>(Expression expression)
{
return new VisitedQueryable<TElement, TVisitor>(_underlyingQueryProvider.CreateQuery<TElement>(Visit(expression)));
}
public IQueryable CreateQuery(Expression expression)
{
var sourceQueryable = _underlyingQueryProvider.CreateQuery(Visit(expression));
var visitedQueryableType = typeof(VisitedQueryable<,>).MakeGenericType(
sourceQueryable.ElementType,
typeof(TVisitor)
);
return (IQueryable)Activator.CreateInstance(visitedQueryableType, sourceQueryable);
}
public TResult Execute<TResult>(Expression expression)
{
return _underlyingQueryProvider.Execute<TResult>(Visit(expression));
}
public object Execute(Expression expression)
{
return _underlyingQueryProvider.Execute(Visit(expression));
}
}
public class VisitedQueryable<T, TExpressionVisitor> : IOrderedQueryable<T>
where TExpressionVisitor : ExpressionVisitor, new()
{
private readonly IQueryable<T> _underlyingQuery;
private readonly VisitedQueryProvider<TExpressionVisitor> _queryProviderWrapper;
public VisitedQueryable(IQueryable<T> underlyingQuery)
{
_underlyingQuery = underlyingQuery;
_queryProviderWrapper = new VisitedQueryProvider<TExpressionVisitor>(underlyingQuery.Provider);
}
public IEnumerator<T> GetEnumerator()
{
return _underlyingQuery.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
public Expression Expression
{
get { return _underlyingQuery.Expression; }
}
public Type ElementType
{
get { return _underlyingQuery.ElementType; }
}
public IQueryProvider Provider
{
get { return _queryProviderWrapper; }
}
}
這裏是一個用法示例:
var linq2ObjectsSource = new List<DateTime?>() { null }.AsQueryable();
var visitedSource = new VisitedQueryable<DateTime?, EntityFunctionsFakerVisitor>(linq2ObjectsSource);
var visitedQuery = visitedSource.Select(dt => EntityFunctions.AddDays(dt, 1));
var results = visitedQuery.ToList();
Assert.AreEqual(1, results.Count);
Assert.AreEqual(null, results[0]);
這樣一來,你的所有期望的特性:
- 開發人員可以繼續使用實體框架定義的標準
EntityFunctions
;
- 如果不在數據庫上運行,生產實現仍然保證會引發異常;
- 查詢可以針對僞造的存儲庫進行測試;
你的問題是什麼? – 2013-02-14 20:38:42
標題是我的問題!如何對方法進行單元測試GetNewValues() – user2073400 2013-02-14 20:43:57
從測試中您將獲得什麼? – 2013-02-14 21:09:57