How to mock two same mongo collection with different results? - mongodb

Question

I have to mock the two aggregate pipeline methods which point to the same collection.
sample Code below
private void GetMethod()
{
var result1 = databaseContext.GetCollection<SampleCollection>("SampleCollection")
.Aggregate<SampleModel>(aggregateQuery, new AggregateOptions { AllowDiskUse = true }).ToList();
var result2 = databaseContext.GetCollection<SampleCollection>("SampleCollection")
.Aggregate<SampleModel>(aggregateQuery, new AggregateOptions { AllowDiskUse = true }).ToList();
}
Below is the code I try to mock the Collection.
List<SampleModel> models = new List<SampleModel>
{
new SampleModel
{
Quarter = 20141,
Type = "AA",
PaidAmount = 100
},
new SampleModel
{
Quarter = 20141,
Type = "BB",
PaidAmount = 200
}
};
var mockMongoCollection = new Mock<IMongoCollection<SampleCollection>>();
var mockCursor = new Mock<IAsyncCursor<SampleModel>>();
mockCursor.Setup(x => x.Current).Returns(models);
mockCursor.SetupSequence(x => x.MoveNext(It.IsAny<CancellationToken>())).Returns(true).Returns(false);
mockMongoCollection.SetupSequence(x => x.Aggregate(It.IsAny<PipelineDefinition<SampleCollection, SampleModel>>(), It.IsAny<AggregateOptions>(), It.IsAny<CancellationToken>()))
.Returns(mockCursor.Object);
this.mockDbContext.Setup(x => x.GetCollection<SampleCollection>(It.IsAny<string>()))
.Returns(mockMongoCollection.Object);
How to mock and set up the different results for each aggregate? . The mock code I tried only working for the first aggregate query.

Answer 1

The key here is to uniquely identify the two invocations for both the pipelines.
If you are certain which pipeline invocation in your test would execute first, you can make use of the SetupSequence to control the return values. You have already used in your MoveNext method mock setup. It wouldn't matter what the pipeline definitions looks like for both.
If that is not the case, then you would need to write conditions to uniquely identify the invocations.
For example:
mockMongoCollection.SetupSequence(c =>
c.Aggregate(
It.Is<PipelineDefinition<SampleCollection, SampleModel>>(x => x.Stages.Count() == 2),
It.IsAny<AggregateOptions>(),
It.IsAny<CancellationToken>()))
.Returns(mockCursor.Object);
The above example simply demonstrates to identify based on how many stages are defined in a pipeline. Say if there were 2 stages in the first pipeline and the second pipeline had 3 stages, then you can use this to setup your mock.
You can also make use of other properties that you can use to express the condition to determine the invocation correctly and setup correct return value.

Answer 2

Got it worked after initialize the individual cursor for each result.
var mockCursorfirstAggregate = new Mock<IAsyncCursor<SampleModel>>();
mockCursorfirstAggregate.Setup(_ => _.Current).Returns(expectedFirstAggregateResult);
mockCursorfirstAggregate
.SetupSequence(_ => _.MoveNext(It.IsAny<CancellationToken>()))
.Returns(true)
.Returns(false);
var mockCursorsecondAggregate = new Mock<IAsyncCursor<SampleModel>>();
mockCursorsecondAggregate.Setup(_ => _.Current).Returns(expectedSecondAggregateResult);
mockCursorsecondAggregate
.SetupSequence(_ => _.MoveNext(It.IsAny<CancellationToken>()))
.Returns(true)
.Returns(false);
this.mockDbContext.SetupSequence(x => x.GetCollection<SampleCollection>(It.IsAny<string>()).Aggregate(It.IsAny<PipelineDefinition<SampleCollection, SampleModel>>(), It.IsAny<AggregateOptions>(), It.IsAny<CancellationToken>()))
.Returns(mockCursorfirstAggregate.Object)
.Returns(mockCursorsecondAggregate.Object);