I am using F# and Foq to write unit tests for a C# project.
I am trying to set up a mock of an interface whose method has an out parameter, and I have no idea how to even start. It probably has to do with code quotations, but that's where my understanding ends.
The interface is this:
public interface IGetTypeNameString
{
bool For(Type type, out string typeName);
}
In C# Foq usage for the interface looks like this:
[Fact]
public void Foq_Out()
{
// Arrange
var name = "result";
var instance = new Mock<IGetTypeNameString>()
.Setup(x => x.For(It.IsAny<Type>(), out name))
.Returns(true)
.Create();
// Act
string resultName;
var result = instance.For(typeof(string), out resultName);
// Assert
Assert.True(result);
Assert.Equal("result", resultName);
}
As for how to achieve that with F#, I am completely lost. I tried something along the lines of
let name = "result"
let instance = Mock<IGetTypeNameString>().Setup(<# x.For(It.IsAny<Type>(), name) #>).Returns(true).Create();
which results in the quotation expression being underlined with an error message of
This expression was expected to have type IGetTypeNameString -> Quotations.Expr<'a> but here has type Quotations.Expr<'b>
Without any indication what types a and b are supposed to be, I have no clue how to correct this.
:?>
(It gets even wilder when I use open Foq.Linq; then the Error List window starts telling me about possible overloads with stuff like Action<'TAbstract> -> ActionBuilder<'TAbstract>, and I get even loster....)
Any assistance or explanation greatly appreciated!
Edit:
So, as stated here, byref/out parameters can not be used in code quotations. Can this be set up at all then in F#?
Foq supports setting up of C# out parameters from C# using the Foq.Linq namespace.
The IGetTypeNameString interface can be easily setup in F# via an object expression:
let mock =
{ new IGetTypeNameString with
member __.For(t,name) =
name <- "Name"
true
}
For declarations that have no analog in F#, like C#'s protected members and out parameters, you can also use the SetupByName overload, i.e.:
let mock =
Mock<IGetTypeNameString>()
.SetupByName("For").Returns(true)
.Create()
let success, _ = mock.For(typeof<int>)
Related
I am using Java code and converting the code in ColdFusion. There are some challenges where I am stuck. This is one function I have in Java:
import com.jayway.jsonpath.JsonPath;
import net.minidev.json.JSONArray;
import net.minidev.json.JSONStyle;
private static String getDetails(String instaDetailsElement) {
String jsonResponse = instaDetailsElement.split(" = ")[1];
JSONArray mediaArray = JsonPath.read(jsonResponse, "$.entry_data.PostPage[:1].graphql.shortcode_media");
String returnJsonString = mediaArray.toJSONString(new JSONStyle(JSONStyle.FLAG_IGNORE_NULL));
System.out.println(returnJsonString);
return returnJsonString;
}
These two lines are giving me some trouble:
var mediaArray = JsonPath.read(jsonResponse, "$.entry_data.PostPage[:1].graphql.shortcode_media");
var returnJsonString = mediaArray.toJSONString(new JSONStyle(JSONStyle.FLAG_IGNORE_NULL));
Here is what I attempted so far. I loaded the jar library for JSON path and tried using it like this:
Application.cfc settings
<cfset this.javaSettings = {LoadPaths = ["cfc/jar"], loadColdFusionClassPath = true, reloadOnChange = false}>
CF Code:
public any function getDetails(String instaDetailsElement) {
var jsonResponse = instaDetailsElement.split(" = ")[1];
var JsonPath = Createobject("java","com.jayway.jsonpath.JsonPath");
writedump(application);
var mediaArray = JsonPath.read(jsonResponse, "$.entry_data.PostPage[:1].graphql.shortcode_media");
writedump(mediaArray); abort;
var returnJsonString = mediaArray.toJSONString(new JSONStyle(JSONStyle.FLAG_IGNORE_NULL));
return returnJsonString;
}
I'm able to view the class methods when I dump the JsonPath object (screen shot), but when I try to call JsonPath.read() I get this error:
No matching Method for read(string, string) found for
com.jayway.jsonpath.JsonPath
TL;DR;
No matching method for read(string, string) found for com.jayway.jsonpath.JsonPath
Technically the error message is correct: there is no read() method that accepts two strings (even though that's how it's used in the java code). The method actually expects three arguments:
Pass in an empty array for the 3rd argument:
JsonPath.read(jsonResponse, "$.entry_data.PostPage[:1].graphql.shortcode_media", []);
Explanation:
String jsonResponse = instaDetailsElement.split(" = ")[1];
JsonPath.read(jsonResponse, "$.entry_data.PostPage[:1].graphql.shortcode_media")
If there really is no read(String, String) method, you might wonder why the java code works at all, since that's exactly what it uses. It works due to a special feature of java.
The documentation shows the overloaded read(..) method actually has three parameters, but one of them is special:
read(String json,
String jsonPath,
Predicate... filters)
Notice the ... after the class name (Predicate)? It's a construct called "varargs" (or variable number of arguments):
You can use a construct called varargs to pass an arbitrary number of values to a method. You use varargs when you don't know how many of a
particular type of argument will be passed to the method. It's a
shortcut to creating an array manually ...
To use varargs, you follow the type of the last parameter by an ellipsis (three dots, ...), then a space, and the parameter name. The
method can then be called with any number of that parameter,
including none.
So in java you're allowed to omit the third argument entirely and call read(String, String) with two strings. ColdFusion doesn't support that syntax, because it creates too much ambiguity. So in lieu of omitting the argument, you can pass in an empty array instead:
JsonPath.read(jsonResponse, "$.entry_data.PostPage[:1].graphql.shortcode_media", []);
(Since this has turned into two questions in one thread, I'm separating the second answer out for clarity ...)
var returnJsonString = mediaArray.toJSONString(new JSONStyle(JSONStyle.FLAG_IGNORE_NULL));
As for translating the JSONStyle code, it helps to unpack nested code from the inside out. Then tackle each piece separately:
mediaArray.toJSONString(new JSONStyle( JSONStyle.FLAG_IGNORE_NULL ));
mediaArray.toJSONString( new JSONStyle( JSONStyle.FLAG_IGNORE_NULL ) )
mediaArray.toJSONString( new JSONStyle( JSONStyle.FLAG_IGNORE_NULL ) )
Piece #1
Uses a static field of the JSONStyle class named FLAG_IGNORE_NULL. To access the field, create a reference to that class:
JsonStyle = createObject("java", "net.minidev.json.JSONStyle");
writeDump(JSONStyle.FLAG_IGNORE_NULL);
Piece #2
Creates a brand new instance of the JSONStyle class, using the static field from above. Use createObject() to create the new instance, passing the static field into the psuedo constructor init():
newJsonStyle = createObject("java", "net.minidev.json.JSONStyle").init(JSONStyle.FLAG_IGNORE_NULL);
writeDump( newJsonStyle );
Piece #3
All that's left is calling the JSONArray.toJSONString() method with the JSONStyle object you just created:
result = mediaArray.toJSONString( newJsonStyle );
writeDump(result);
I have been tasked with writing a unit test for the following Web API 2 action:
public HttpResponseMessage Get()
{
IEnumerable<KeyValuePair<long, string>> things = _service.GetSomething();
return ActionContext.Request.CreateResponse(things.Select(x => new
{
Thing1 = x.Prop1.ToString(),
Thing2 = x.Prop2
}).ToArray());
}
I am testing the status code and that works fine, but I have not been able to figure out how I can extract the content data and test it. Here's my test so far:
[TestMethod]
public void GetReturnsOkAndExpectedType()
{
var controller = GetTheController();
var response = controller.Get();
Assert.AreEqual(HttpStatusCode.OK, response.StatusCode);
dynamic responseContent;
Assert.IsTrue(response.TryGetContentValue(out responseContent));
//???? How can I cast/convert responseContent here ????
}
If I debug the test and inspect responseContent in the immediate window, I see this (I have mocked/stubbed in a single fake value for testing):
{<>f__AnonymousType1<string, string>[1]}
[0]: { Thing1 = "123", Thing2 = "unit test" }
I can cast this as an array of object, but if I try and extract the values by their property names, I get an error (immediate window again):
((object[])responseContent)[0].Thing1
'object' does not contain a definition for 'Thing1' and no extension method 'Thing1' accepting a first argument of type 'object' could be found (are you missing a using directive or an assembly reference?)
Similarly, if I try to cast and project to an anonymous type of the same shape, it will not compile:
//Thing1 and Thing2 get red-lined here as 'cannot resolve symbol'
var castResult = ((object[]) responseContent).ToList().Select(x => new {x.Thing1, x.Thing2});
I know I can probably achieve what I want to do if I serialize/deserialize everything using something like JsonConvert, but that doesn't seem like the "right" way to do it. I feel like I'm missing something fundamental, here. How can I cast/convert an anonymous type from HttpResponseMessage for unit testing?
As has been said by #Daniel J.G. in the comments above, one option would be to use reflection to fetch the values of your properties. Since you appear to be using MS testing framework another alternative is to use the PrivateObject class to do some of the reflection work for you.
So, you could do something like this in your test:
var poContent = ((object[])responseContent).Select(x => new PrivateObject(x)).ToArray();
Assert.AreEqual("123", poContent[0].GetProperty("Thing1"));
Assert.AreEqual("unit test", poContent[0].GetProperty("Thing2"));
How do I test which view was rendered from a controller action if what I get is a T4MVC_ActionResult? Under normal circumstances I should be able to directly use TestHelper's methods, like in the examples:
pooController.Details().AssertViewRendered().ForView("Details")
...but, since through T4MVC I get a T4MVC_ActionResult instead of a ViewResult, the part AssertViewRendered<>().ForView("Details") fails. What alternative do I have if I want to test which view was invoked?
UPDATE:
Here's the test code:
[TestMethod]
public void Theme_Controller_Details_Action_Returns_Details_View()
{
var builder = new TestControllerBuilder();
var mockThemeRepository = new Mock<IThemeRepository>();
var themeController = builder.CreateController<Evalgrid.Website.Controllers.ThemeController>(mockThemeRepository.Object);
builder.InitializeController(themeController);
var result = themeController.Details();
result.AssertViewRendered().ForView("Details");
}
I used the debugger setting a breakpoint after the result line, and its variable type is T4MVC_ActionResult, while themeController is Evalgrid.Website.controllers.ThemeController. Note that I have used the fully qualified name of the controller.
I get this:
Expected result to be of type
ViewResult. It is actually of type
T4MVC_ActionResult.
I don't know what's going on.
Actually, T4MVC should not make a difference here. If you directly instantiate your controller and call an action method, you'll get the same thing back whether you use T4MVC or not. i.e. you won't get a T4MVC_ActionResult.
It's only when you write MVC.Foo.Details() that you'll get a T4MVC_ActionResult. That's because MVC.Foo returns an instance of a derived class which does special thing, and not directly your controller class.
Does that make sense?
Update: I'm confused, as looking at the sources for TestControllerBuilder.CreateController, it has:
public T CreateController<T>(params object[] constructorArgs) where T : Controller
{
var controller = (Controller)Activator.CreateInstance(typeof(T), constructorArgs);
InitializeController(controller);
return controller as T;
}
So it's directly instantiating the type that you pass in, which should just call your normal action.
One question about your code: does your Details action method take any parameters? If so, that would explain the problem, as you're calling it with no params, which would be a T4MVC method added in the partial class.
I'd like to write F# unit test with mock objects. I'm using NUnit.
But unfortunately I couldn't find any examples.
Here's an example of the code under test:
type ICustomer = interface
abstract Id: int with get
abstract Name: string with get
abstract CalculateBalanceWithDiscount: decimal -> decimal
end
type Customer = class
val id: int
val name: string
val balance: decimal
new(id, name, balance) =
{id = id; name = name; balance = balance}
interface ICustomer with
member this.Id
with get () = this.id
member this.Name
with get () = this.name
member this.CalculateBalanceWithDiscount discount =
this.balance - (discount * this.balance)
end
end
As a side-note, you can use implicit constructor syntax to make your class declaration a bit nicer. You can also simplify readonly properties, because you can omit with get():
// F# infers that the type is an interface
type ICustomer =
abstract Id : int
abstract Name : string
abstract CalculateBalanceWithDiscount : decimal -> decimal
// Parameters of the implicit constructor are autoamtically
// accessible in the body (they are stored as fields)
type Customer(id:int, name:string, balance:decimal) =
interface ICustomer with
member this.Id = id
member this.Name = name
member this.CalculateBalanceWithDiscount(discount) =
balance - (discount * balance)
Regarding testing - do you have any example of what you're trying to achieve? I'm sure we can help for example with translating code from C#. Or what kind of tests would you like to write using mocking?
In general, a nice thing about F# and functional languages is that you can usually test code more easily without using any mocks. Functional programs are written in a different style:
In functional programming, a function takes all it's inputs as arguments and the only thing that it does is that it calculates and returns some result. This is also true for methods of immutable object types - they do not modify any state of any objects
Mocks are typically used for two purposes:
To verify that the tested operation performed some call to a method of a referenced object e.g. prod.Update(newPrice) to update the state of the object. However, in functional programming the method should instead return the new state as the result - so you don't need mock object. Just check whether the new returned state is what you expected.
To load create a fake component of the application, for example instead of loading data from the database. Again, a purely functional function should take all it's inputs as arguments. This means that you don't need to create a mock object - you just call the function with some test data as argument (instead of data loaded from database).
In summary, this means that in a well-designed functional program, you should be able to write all unit tests simply as checks that verify that some function returns the expected result for the expected arguments. Of course, this isn't strictly true in F#, because you may need to interoperate with other impure .NET components (but that can be answered only if you give a more specific example).
You don't need to create a class in order to create mocks:
/// customer : int -> string -> decimal -> ICustomer
let customer id name balance =
{new ICustomer with
member this.Id = id
member this.Name = name
member this.CalculateBalanceWithDiscount discount =
balance - (discount * balance) }
Is it possible to mock a stub/mock's object member call without having to define that as a stub, and also set the return value as all seperate verbose lines?
Example:
[TestMethod]
public void AssignedPermissions_AssociateExists_ReturnsEdit_Rhino()
{
//Arrange
var fakeConfiguration = MockRepository.GenerateStub<IDomainControllerConfiguration>();
var fakeAssociateRepository = MockRepository.GenerateStub<IAssociateRepository>();
fakeConfiguration.Stub(x => x.AssociateRepository).Return(fakeAssociateRepository);
fakeAssociateRepository.Stub(x=>x.GetAssociatesByRole(null,false,null)).IgnoreArguments()
.Return(new IAssociate[]{MockRepository.GenerateStub<IAssociate>()});
var domain = new DomainController(fakeConfiguration);
const AssignedPermission expected = AssignedPermission.Edit;
//Act
AssignedPermission actual = domain.AssignedPermissions();
//Assert
Assert.AreEqual(expected, actual);
}
Are all those temporary variables necessary just to stub out nested method calls?
I've never used the functionality, so I'm not 100% certain that this will work, but theoretically Rhino mocks supports "recursive mocking", which should allow you to at least cut out the fakeAssociateRepository by doing something like this:
var fakeConfiguration = MockRepository.GenerateStub<IDomainControllerConfiguration>();
fakeConfiguration.Stub(x => x.AssociateRepository.GetAssociatesByRole(null,false,null))
.IgnoreArguments()
.Return(new IAssociate[]{MockRepository.GenerateStub<IAssociate>()});
var domain = new DomainController(fakeConfiguration);
(note: code not tested, or even compiled)
Just wanted to share my input on this, since I just spent the last few hours wrestling with it. The answer posted above by Alconja absolutely works, but if you plan to use it for "AssertWasCalled" type of assertion, it does not assert the way I expected it to. It seems that the AssertWasCalled methods tried to assert the "get accessor" associated with the "nested" object.
For instance, if you wanted to do this:
fakeconfiguration.AssertWasCalled(x => x.AssociateRepository.GetAssociatesByRole(null, false, null));
You would get an exception such as
System.InvalidOperationException : Previous method 'IDomainControllerConfiguration.get_AssociateRepository();' requires a return value or an exception to throw.
Because the AssertWasCalled is asserting the get-accessor of the AssociateRepository property, rather than the GetAssociatesByRole() method. In the end, for my case I had to use the OP's methodology of creating mutliple stubs.