A FluentAssertion extension to easily assert on callbacks.
License
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1
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Published
Jan 12, 2024
$ dotnet add package FluentAssertions.CallbacksA FluentAssertion extension to easily assert on callbacks.
In our projects, we often take a more functional approach and inject callbacks. A lot. The test code often looked like this:
public void BadUnitTest
{
// Arrange
int? arg1;
string? arg2;
var testCallback = (int a1, string a2) =>
{
arg1 = a1;
arg2 = a2;
};
var sut = new Sut();
// Act
sut.DoSomething(testCallback);
// Assert
arg1.Should().Be(42);
arg2.Should().Be("Hello World");
}
To avoid the overhead of storing the arguments in local variables, I created this extension.
Add the FluentAssertions.Callbacks NuGet package to your test project.
using FluentAssertions.Callbacks;
public void GoodUnitTest()
{
var testCallback = new CallbackSpy<int, string>();
var sut = new Sut();
sut.DoSomething(testCallback.Callback);
testCallback.Should().HaveBeenCalledWith(42, "Hello World");
// The following assertions are also possible
testCallback.Should().HaveBeenCalled();
testCallback.Should().HaveBeenCalledWith(Arg<int>.Is(x => x > 40), "Hello World");
}