C#. Fluent Assertions

Should

Fluent Assertions Should: Used to assert that the actual result of an operation meets the expected condition.

Basic Assertions

# Equal Assertions
result.Should().Be(expected);

# Null Assertions
object.Should().BeNull();
object.Should().NotBeNull();

# Not Equal
result.Should().NotBe(unexpected);

# Greater Than / Less Than
result.Should().BeGreaterThan(value);
result.Should().BeLessThan(value);

Collection Assertions

# Contain Items
collection.Should().Contain(expectedItem);

# Be Empty / Have Count
collection.Should().BeEmpty();
collection.Should().HaveCount(expectedCount);

# Contain Exactly
collection.Should().ContainInOrder(expectedItems);

Exception Assertions

Links:

https://fluentassertions.com/exceptions/

There are 2 ways of testing exceptions:

Using Action
Using Invoking

Using Action

If you prefer the arrange-act-assert syntax, you can also use an action in your act part.

# Act
Action act = () => _sut.Foo2("Hello");

# Assert
act.Should().Throw<InvalidOperationException>()
    .WithInnerException<ArgumentException>()
    .WithMessage("whatever");

Using Invoking

# Act & Assert
_sut.Invoking(y => y.Foo("Hello"))
    .Should().Throw<InvalidOperationException>()
    .WithMessage("Hello is not allowed at this moment");

Object Assertions

# Be Equivalent To
actualObject.Should().BeEquivalentTo(expectedObject);

# Have Property
actualObject.Should().HaveProperty("PropertyName").Which.Should().Be(expectedValue);

Installation

dotnet add package FluentAssertions