internal static void AssertDeferred <T>(Func <IEnumerable <int>, IEnumerable <T> > deferredFunction)
{
ThrowingEnumerable source = new ThrowingEnumerable();
var result = deferredFunction(source);
using (var iterator = result.GetEnumerator())
{
Assert.Throws <InvalidOperationException>(() => iterator.MoveNext());
}
}
public void FirstSequenceIsNotAccessedBeforeUse()
{
var first = new ThrowingEnumerable();
var second = new int[] { 5 };
var query = first.Concat(second);
using (var iterator = query.GetEnumerator())
{
Assert.Throws <InvalidOperationException>(() => iterator.MoveNext());
}
}
public void FirstSequenceNotUsedUntilQueryIterated()
{
var first = new ThrowingEnumerable();
int[] second = { 2 };
var query = first.Union(second);
using (var iterator = query.GetEnumerator())
{
// No exception thrown until here.
Assert.Throws <InvalidOperationException>(() => iterator.MoveNext());
}
}
public void AlternateExceptionExpectation()
{
int[] first = { 3, 5, 3 };
var second = new ThrowingEnumerable();
using (var iterator = first.Union(second).GetEnumerator())
{
Assert.IsTrue(iterator.MoveNext());
Assert.AreEqual(3, iterator.Current);
Assert.IsTrue(iterator.MoveNext());
Assert.AreEqual(5, iterator.Current);
iterator.MoveNext();
}
}
public void SecondSequenceNotUsedUniltFirstIsExhausted()
{
int[] first = { 3, 5, 3 };
var second = new ThrowingEnumerable();
using (var iterator = first.Union(second).GetEnumerator())
{
Assert.IsTrue(iterator.MoveNext());
Assert.AreEqual(3, iterator.Current);
Assert.IsTrue(iterator.MoveNext());
Assert.AreEqual(5, iterator.Current);
Assert.Throws <InvalidOperationException>(() => iterator.MoveNext());
}
}
public void SecondSequenceIsNotAccessedBeforeUse()
{
var first = new int[] { 5 };
var second = new ThrowingEnumerable();
var query = first.Concat(second);
using (var iterator = query.GetEnumerator())
{
// MoveNext will succeed as there is an element in first.
Assert.IsTrue(iterator.MoveNext());
Assert.AreEqual(5, iterator.Current);
// This will fail as the second sequence doesn't support MoveNext().
Assert.Throws <InvalidOperationException>(() => iterator.MoveNext());
}
}
public void ExecutionIsDeferred()
{
ThrowingEnumerable.AssertDeferred(src => src.Select(x => x * 2));
}
public void WithIndexExecutionIsDeferred()
{
ThrowingEnumerable.AssertDeferred(src => src.Select((s, index) => s + index));
}
public void Have_deffered_execution_when_index_provided()
{
ThrowingEnumerable.AssertDeferred(src => src.Where((x, index) => x > 0));
}
public void Have_deffered_execution()
{
ThrowingEnumerable.AssertDeferred(src => src.Where(x => x > 0));
}
public void ExecutionIsDeferred()
{
ThrowingEnumerable.AssertDeferred <int>(src => src.Where(x => x > 0));
}
public void WithIndexExecutionIsDeferred()
{
ThrowingEnumerable.AssertDeferred(src => src.Where((x, index) => x > 0));
}