Class TestExtractor<T>

Namespace
Wolfgang.Etl.TestKit
Assembly
Wolfgang.Etl.TestKit.dll

An in-memory extractor for use in tests, examples, and benchmarks. Yields items from either an IEnumerable<T> or an IEnumerator<T>, depending on which constructor is used.

public class TestExtractor<T> : ExtractorBase<T, Report>, IExtractWithProgressAndCancellationAsync<T, Report>, IExtractWithCancellationAsync<T>, IExtractWithProgressAsync<T, Report>, IExtractAsync<T> where T : notnull

Type Parameters

T

The type of item to extract.

Inheritance
ExtractorBase<T, Report>
TestExtractor<T>
Implements
IExtractWithProgressAndCancellationAsync<T, Report>
IExtractWithCancellationAsync<T>
IExtractWithProgressAsync<T, Report>
IExtractAsync<T>
Inherited Members
ExtractorBase<T, Report>.ExtractAsync()
ExtractorBase<T, Report>.CreateProgressReport()
ExtractorBase<T, Report>.IncrementCurrentItemCount()
ExtractorBase<T, Report>.IncrementCurrentSkippedItemCount()
ExtractorBase<T, Report>.ReportingInterval
ExtractorBase<T, Report>.CurrentItemCount
ExtractorBase<T, Report>.CurrentSkippedItemCount
ExtractorBase<T, Report>.MaximumItemCount
ExtractorBase<T, Report>.SkipItemCount

Examples

// From a list:
var items = new List<int> { 1, 2, 3, 4, 5 };
var extractor = new TestExtractor<int>(items);

// From an on-the-fly generator — avoids allocating a million-item list:
static IEnumerator<int> Generate(int count)
{
    for (var i = 0; i < count; i++)
        yield return i;
}

var extractor = new TestExtractor<int>(Generate(1_000_000));

Remarks

Use the IEnumerable<T> constructor when your data is already materialized in a collection. The enumerable is re-evaluated on each call to ExtractAsync, so the extractor can be reused across multiple runs.

Use the IEnumerator<T> constructor when you need to generate large volumes of data on the fly (e.g. via a generator method with yield return) without materializing all items in memory at once. The caller owns the enumerator's lifetime — the extractor does not dispose it.

Set Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.SkipItemCount to skip the first N items before yielding. Set Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.MaximumItemCount to stop after yielding that many items. Both default to their base-class values (0 and MaxValue respectively).

Constructors

TestExtractor(IEnumerable<T>)

Initializes a new TestExtractor<T> that yields items from the specified IEnumerable<T>.

public TestExtractor(IEnumerable<T> items)

Parameters

items IEnumerable<T>

The sequence of items to extract. The enumerable is evaluated lazily on each extraction run, so the same extractor instance can be reused.

Exceptions

ArgumentNullException

items is null.

TestExtractor(IEnumerable<T>, IProgressTimer)

Initializes a new TestExtractor<T> that yields items from the specified IEnumerable<T> and uses the supplied Wolfgang.Etl.Abstractions.IProgressTimer to drive progress callbacks.

protected TestExtractor(IEnumerable<T> items, IProgressTimer timer)

Parameters

items IEnumerable<T>

The sequence of items to extract.

timer IProgressTimer

The timer used to drive progress callbacks. Inject a ManualProgressTimer in tests to fire callbacks on demand.

Exceptions

ArgumentNullException

items or timer is null.

TestExtractor(IEnumerator<T>)

Initializes a new TestExtractor<T> that yields items from the specified IEnumerator<T>.

public TestExtractor(IEnumerator<T> enumerator)

Parameters

enumerator IEnumerator<T>

The enumerator to draw items from. Useful for generator methods that produce large volumes of data on demand without allocating a full collection in memory. The caller is responsible for the enumerator's lifetime — the extractor does not dispose it.

Exceptions

ArgumentNullException

enumerator is null.

TestExtractor(IEnumerator<T>, IProgressTimer)

Initializes a new TestExtractor<T> that yields items from the specified IEnumerator<T> and uses the supplied Wolfgang.Etl.Abstractions.IProgressTimer to drive progress callbacks.

protected TestExtractor(IEnumerator<T> enumerator, IProgressTimer timer)

Parameters

enumerator IEnumerator<T>

The enumerator to draw items from. The caller is responsible for the enumerator's lifetime — the extractor does not dispose it.

timer IProgressTimer

The timer used to drive progress callbacks. Inject a ManualProgressTimer in tests to fire callbacks on demand.

Exceptions

ArgumentNullException

enumerator or timer is null.

Methods

CreateProgressReport()

Creates a progress report of type TProgress. This gives the derived class the opportunity to implement a custom progress report that is specific to the extraction process.

protected override Report CreateProgressReport()

Returns

Report

Progress of type TProgress

CreateProgressTimer(IProgress<Report>)

Creates the Wolfgang.Etl.Abstractions.IProgressTimer used to drive progress callbacks. Override this method in a derived class to inject a custom timer (for example, a custom implementation that allows manual control in unit tests).

protected override IProgressTimer CreateProgressTimer(IProgress<Report> progress)

Parameters

progress IProgress<Report>

The progress sink that will receive callbacks.

Returns

IProgressTimer

A started Wolfgang.Etl.Abstractions.IProgressTimer instance.

ExtractWorkerAsync(CancellationToken)

This method is the core implementation of the extraction logic and should be overridden by derived classes.

protected override IAsyncEnumerable<T> ExtractWorkerAsync(CancellationToken token)

Parameters

token CancellationToken

A CancellationToken to observe while waiting for the task to complete.

Returns

IAsyncEnumerable<T>

IAsyncEnumerable<TSource> The result may be an empty sequence if no data is available or if the extraction fails.

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