Compare Objects from Tables in SpecFlow

Earlier this week, I wrote about how to create and populate objects from tables created in your SpecFlow scenarios. If the only reason you’re populating an object is to do a comparison, there’s an easier way: the CompareToInstance<T> method.

Similar to the previously discussed method, CreateInstance<T>, an object will be created using the properties contained in a table of values. The object properties will be matched ignoring case and whitespace. CompareToInstance allows you to provide an instance of the same type and does a property-by-property comparison. If any of the property values are different, a TechTalk.SpecFlow.Assist.ComparisonException is thrown with a message containing all differences that were found.

Here’s an example!

Scenario: Update a person name
	Given I have an existing person
	And I change the name to the following
		| first | middle | last  |
		| Ftest | Mtest  | Ltest |
	When I save the person
	And I retrieve person
	Then the name was changed to the following
		| first | middle | last  |
		| Ftest | Mtest  | Ltest |
// don't forget!
// using TechTalk.SpecFlow.Assist;

[Given(@"I change the name to the following")]
public void GivenIChangeTheNameToTheFollowing(Table table)
{
    var p = ScenarioContext.Current.Get<Person>();
    p.Name = table.CreateInstance<NameType>();
}

[Then(@"the name was changed to the following")]
public void ThenTheNameWasChangedToTheFollowing(Table table)
{
    var p = ScenarioContext.Current.Get<Person>();
    table.CompareToInstance<NameType>(p.Name);
}
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