Unit test of the second method call

Question

I have a unit test where I am using Moq and Fluent Assertions:

[Fact]
public void GetSymbols_ShouldSetSucceedToTrue_WhenSecondAttemptSucceed()
{
    string selectedFileName = "testFileName.txt";
    string[] expectedResult = new string[] { "testSymbol1", "testSymbol2" };
    Mock<IOpenFileDialogService> mockFileDialogService = new Mock<IOpenFileDialogService>();
    mockFileDialogService.SetupSequence(m => m.ShowDialog()).Returns(false).Returns(true);
    mockFileDialogService.Setup(m => m.FileName).Returns(selectedFileName);
    Mock<IFileService> mockFileService = new Mock<IFileService>();
    mockFileService.Setup(m => m.ReadAllLines(selectedFileName)).Returns(expectedResult);
    SymbolsProviderFromFile spff = new SymbolsProviderFromFile(mockFileDialogService.Object, mockFileService.Object);

    // Act
    spff.GetSymbols();
    IEnumerable<string> result = spff.GetSymbols();

    // Assert
    using (new AssertionScope())
    {
        result.Should().Equal(expectedResult);
        spff.Succeed.Should().BeTrue();
    }
}

I would like to check the second call of my method. Unfortunately when I debug this code, the spff.GetSymbols() method is only called once and it is called on the result.Should().Equals(expectedResult) line when the result is checked. There is some kind of a lazy loading here - the method is only called when the result is needed. Why is it not called immediately in the spff.GetSymbols() line? How can I change this behavior and how can I call testing method twice in unit test?

hi, just add .ToList() to end of first call; spff.GetSymbols().ToList(). — Erkan, Mar 23 '22 at 20:33
Exactly. I'm 100% confident that your method `GetSymbols` is called twice. But I suspect that your implementation uses LINQ, `yield` or something like that. — Dennis Doomen, Mar 24 '22 at 06:25
@DennisDoomen yes, implementation of the `GetSymbols()` method uses `yield`. So maybe here is the reason why it is not called immediately? — Qwertyluk, Mar 24 '22 at 07:31

score 0 · Accepted Answer · answered Apr 01 '22 at 06:18

0

Problem has been resolved thanks to @Dennis Doomen.

An issue about not executing method immediately was in the implementation of the spff.GetSymbols() method which uses yield return so it wasn't really related to unit testing.

answered Apr 01 '22 at 06:18

Qwertyluk

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Unit test of the second method call

1 Answers1