· javascript

Treating Javascript as an integration point

A couple of weeks ago I wrote a post about my software development journey over the last year and towards the end I described the difficulties we were having in making changes to some C# code while being sure that we hadn’t broken javascript functionality that also relied on that code.

We typically have code which looks like this:

public class SomeController
	public ActionResult SomeControllerAction()
		var someModel = new SomeModel { Property1 = "my Property" };

		return new JsonResult { Data = someModel };

public class SomeModel
	public string Property1 { get; set; }

We would make use of this type of object in javascript code like so:

			var value = data.Property1;
			// do some cool stuff with that value

My colleague Raymond Maung recently came up with the idea of writing tests to ensure that the properties we make use of in Javascript exist on the C# objects which we return in JSON calls.

We now have a testing extension method which uses reflection to check that the expected properties are set.

public static class TestingExtensions
        public static void AssertHasProperty(this Type type, string propertyName)
            var property = type.GetProperty(propertyName);
            Assert.IsNotNull(property, "Expected {0} to have property '{1}' but it didn't", type.Name, propertyName);
public void ShouldEnsurePropertiesRequiredInJavascriptAreSet()
	var type = typeof(SomeModel);
	// and so on

It still requires the developer to remember to put a test in if they add a property to the C# model but I think it’s working better than having to switch between the javascript and C# files checking that you haven’t broken anything.

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