The approach I am following now is creating a wrapper around the class providing the static method, and then mocking this wrapper instead of mocking the real class, as in:
class TestClass {
final ThirdPartyClassWrapper _thirdPartyClassWrapper;
TestClass(this._thirdPartyClassWrapper);
void someMethod() {
_thirdPartyClassWrapper.doSomething();
}
}
class ThirdPartyClass {
static void doSomething() {}
}
class ThirdPartyClassWrapper {
void doSomething() {
ThirdPartyClass.doSomething();
}
}
//now I can mock the class and control the behaviour of the method
//but there is alot of boilerplate code
class MockThirdPartyClassWrapper extends Mock implements ThirdPartyClassWrapper{}
But as you see a lot of boilerplate is introduced.
So is there a better way to solve the problem?
Related
I was doing some unit testing in flutter with mockito, and I feels unable to verify a method is called within another method. The code I've written so far as follows,
The class I want to test
class A {
void doSomething() {
callMe();
}
void callMe() {}
}
Mocked class
class MockA extends Mock implements A {}
The test I wrote,
test("Test method is called", () {
A a = new MockA();
a.doSomething();
verify(a.callMe()).called(1);
});
When I run the above test I am getting an error
No matching calls. All calls: MockA.doSomething()
(If you called `verify(...).called(0);`, please instead use `verifyNever(...);`.)
If i verify doSomething is called it works, but for a call on callMe within doSomething doesn't work. Is this the default behavior or am I doing something wrong? Please note I need to verify the callMe() method is called when doSomething() is called.
You mocked A and replaced it with MockA. Mocks have no implementation. MockA.doSomething() does nothing and does not and cannot call MockA.callMe().
That A.doSomething() calls A.callMe() should be considered an implementation detail of of doSomething(); making a test rely on that would tightly couple the test to the specific implementation and would be brittle.
You can't use a mock to verify the implementation of the thing being mocked. If you want to verify the implementation of A.doSomething(), you instead should use an actual object and verify observable properties on that object.
But if you still really want to do this, then you would need to modify A to not call methods on itself and to instead call methods on a provided object (i.e., "dependency injection"). For example:
class A {
final late A a;
A({A? a}) {
this.a = a ?? this;
}
void doSomething() {
a.callMe();
}
void callMe() {}
}
test("Test method is called", () {
var mockA = MockA();
var actualA = A(a: mockA);
actualA.doSomething();
verify(mockA.callMe()).called(1);
});
It's a bit unusual for a class to depend on a mock of itself, however, and it would not scale if you then want to verify calls made by callMe().
Another approach that would scale better (but with significantly more work) would be to create your own fake class that tracks method calls:
class TrackedA implements A {
int doSomethingCallCount = 0;
int callMeCallCount = 0;
#override
void doSomething() {
doSomethingCallCount += 1;
super.doSomething();
}
#override
void callMe() {
callMeCallCount += 1;
super.callMe();
}
}
But again, that's very brittle, and I would not recommend it.
Currently making a large app with Flutter and I m stuck on the architecture of service class. There is a service class for the firestore CRUD operations.This class has many methods and I want split it into small pieces. I use an abstract class to protect methods.I find a way with mixins but don't know it's a good one or not.
https://gist.github.com/pMertDogan/fcd301d768f3980a898cec33a9acaa4f.
//Extend CRUDSERVICE rules aka abstract class => Test
mixin Update{
void updateSomething();
}
mixin Read{
void readSomething();
}
//BASE class for CRUDSERVICE
abstract class Test with Update,Read{
doSomeCreateOP(String x);
}
//
class CrudService extends Test with UpdateService , ReadService{
#override
doSomeCreateOP(String x) {
print('crated ' + x);
}
}
mixin UpdateService{
// #override
void updateSomething() {
print('updated');
}
}
mixin ReadService{
// #override
void readSomething() {
print('read');
}
}
void main() {
CrudService croudService = CrudService();
croudService.doSomeCreateOP(' dartSide');
croudService.updateSomething();
croudService.readSomething();
}
CreateService and UpdateService mixins are just sample.I am thinking like if I need update user information all methods are handed by UserServiceMix mixin if it's Friend then its hanled by FriendServiceMix so I can split them like a domain-based.Each mixin is responsible for specific operations.I can manage then on independent files and summary of them with the help of mixin.
Is it good way to go?
I believe it is a good way to go. It is a quite flexible approach. We use it for API versioning as well.
abstract class Service {
void method1();
void method2();
}
mixin Method1V1 {
void method1() {
print("method1");
}
}
mixin Method2V1 {
void method2() {
print("method2");
}
}
mixin Method2V2 {
void method2() {
print("method2 with changed logic");
}
}
class ServiceV1 extends Service with Method1V1, Method2V1 {
}
class ServiceV2 extends Service with Method1V1, Method2V2 {
}
void main() {
final version = 2;
final Service service = version == 1 ? ServiceV1() : ServiceV2();
service.method2();
}
Maybe it's really dumb question. But I cannot believe there is no resources, where it's described. Even from the official documentation. What I'm trying to do, it's create Anonymous class for the next function.
How to create Anonymous class in Dart with custom function something like next in Kotlin?
Handler(Looper.getMainLooper()).post(Runnable() {
#override
open fun run() {
//...
}
private fun local() {
//....
}
})
Dart does not support creating an anonymous class.
What you're trying to do is not possible.
On the other hand, you can create anonymous functions. So you could use that to mimic an anonymous class.
The idea is to add a constructor of your abstract class, that defer its implementation to callbacks.
abstract class Event {
void run();
}
class _AnonymousEvent implements Event {
_AnonymousEvent({void run()}): _run = run;
final void Function() _run;
#override
void run() => _run();
}
Event createAnonymousEvent() {
return _AnonymousEvent(
run: () => print('run'),
);
}
It's not strictly the same as an anonymous class and is closer to the decorator pattern. But it should cover most use-cases.
This is an alternative way, but not fully equivalent:
Problem, e.g.:
I would like to implement OnChildClickListener inline in my code without class. For this method:
void setOnChildClickListener(OnChildClickListener listener) {
...
}
Instead of this:
abstract class OnChildClickListener {
bool onChildClick(int groupPosition, int childPosition);
}
use this:
typedef OnChildClickListener = Function(int groupPosition, int childPosition);
And in code you can implement it in this way:
listView.setOnChildClickListener((int groupPosition, int childPosition) {
// your code here
});
In other words do not use abstract class, but use typedef.
There are three classes.
// in external library, which I don't want to modify
class ComponentBase {
// I want calling this to be disallowed
forceUpdate() {}
}
class ComponentBase_MyVersion extends ComponentBase {
// I want subclasses to always call this, instead of forceUpdate()
Update() {}
}
class MyComponent extends ComponentBase_MyVersion {
DoSomething() {
// I want this to be disallowed
this.forceUpdate();
// forcing the subclass to call this instead
this.Update();
}
}
How can I accomplish this, with changes only to ComponentBase_MyVersion?
Is there a way to "hide" a base-class member?
Or perhaps a way to override the definition -- like with the "new" keyword in C# -- letting me mangle the method definition to at least make warnings appear when attempting to call it?
The OOP does not allow you to do this kind of method cancellation. You can impleement this funcion on your class with an Exception like you suggested, or use a composition: https://en.wikipedia.org/wiki/Composition_over_inheritance
Example 1:
class ComponentBase {
forceUpdate() {}
}
class ComponentBase_MyVersion extends ComponentBase {
Update() {}
forceUpdate() {
throw new Error("Do not call this. Call Update() instead.");
}
}
class MyComponent extends ComponentBase_MyVersion {
DoSomething() {
// wil raise an exception
this.forceUpdate();
this.Update();
}
}
Example 2 (composition):
class ComponentBase {
forceUpdate() {}
}
class ComponentBase_MyVersion {
private _component: ComponentBase = ...;
Update() {}
// expose _component desired members ...
}
class MyComponent extends ComponentBase_MyVersion {
DoSomething() {
// compilation error
this.forceUpdate();
this.Update();
}
}
I hope I helped.
Encapsulate implementation by replacing inheritance with composition Delegation Pattern
You can do this by adding the private access modifier on the forceUpdate method. This will result in all the subclasses being unable to access forceUpdate. However TypeScript does not support package access modifiers, but you can do this by replacing inheritance with composition.
class ComponentBase {
forceUpdate() {
}
}
class ComponentBase_MyVersion {
// Replace inheritance with composition.
private component: ComponentBase;
Update() {
this.component.forceUpdate();
}
}
class MyComponent extends ComponentBase_MyVersion {
DoSomething() {
// Now subclass can't access forceUpdate method
this.Update();
}
}
Use a symbol in order to prevent external access to the method.
If you don't want to replace inheritance with composition, you can use Symbol to define a method. If your target is es5 you must configure tsconfig.json compilerOptions.lib to include es2015.symbol. Because every symbol is unique, any external module will not be able to obtain the symbol and access the method.
// libs.ts
let forceUpdate = Symbol("forceUpdate");
export class ComponentBase {
[forceUpdate]() {
}
}
export default class ComponentBase_MyVersion extends ComponentBase {
Update() {
this[forceUpdate]();
}
}
// test.ts
import ComponentBase_MyVersion from "./libs";
class MyComponent extends ComponentBase_MyVersion {
DoSomething() {
// Now subclass can't access the forceUpdate method.
this.Update();
}
}
I found a way that seems to work -- that is, which causes warnings to appear when someone attempts to call forceUpdate() on a subclass instance.
forceUpdate(_: ()=>"Do not call this. Call Update() instead.") {
throw new Error("Do not call this. Call Update() instead.");
}
Now when I write new MyComponent().forceUpdate(), I get a compiler error, with the warning message containing a description telling me to use Update() instead.
EDIT: Apparently this only works because the base class already had this definition:
forceUpdate(callBack?: () => any): void;
If instead the base method is defined with no arguments originally (as in the OP), the above solution doesn't work.
However, if you have a case like mine (where there's an optional property like that, which you can narrow the return-type of), it works fine. (not sure if this return-type-narrowing is a bug, or intended)
I want to mock a Class in Mockito. It will then have a .newInstance() call issued which will be expected to return an actual class instance (and will return a mock in my case).
If it was setup correctly then I could do:
ArrayList myListMock = mock(ArrayList.class);
when(myVar.newInstance()).thenReturn(myListMock);
I know I can set it up so that a new instance of class ArrayList will be a mock (using PowerMockito whenNew), just wondering if there was a way to mock this kind of a class object so I don't have to override instance creation...
Below is the real class I'm trying to mock, I can't change the structure it is defined by the interface. What I'm looking for is a way to provide cvs when initialize is called.
public class InputConstraintValidator
implements ConstraintValidator<InputValidation, StringWrapper> {
Class<? extends SafeString> cvs;
public void initialize(InputValidation constraintAnnotation) {
cvs = constraintAnnotation.inputValidator();
}
public boolean isValid(StringWrapper value,
ConstraintValidatorContext context) {
SafeString instance;
try {
instance = cvs.newInstance();
} catch (InstantiationException e) {
return false;
} catch (IllegalAccessException e) {
return false;
}
}
Mockito is designed exclusively for mocking instances of objects. Under the hood, the mock method actually creates a proxy that receives calls to all non-final methods, and logs and stubs those calls as needed. There's no good way to use Mockito to replace a function on the Class object itself. This leaves you with a few options:
I don't have experience with PowerMock but it seems it's designed for mocking static methods.
In dependency-injection style, make your static factory method into a factory instance. Since it looks like you're not actually working with ArrayList, let's say your class is FooBar instead:
class FooBar {
static class Factory {
static FooBar instance;
FooBar getInstance() {
if (instance == null) {
instance = new FooBar();
}
return instance;
}
}
// ...
}
Now your class user can receive a new FooBar.Factory() parameter, which creates your real FooBar in singleton style (hopefully better and more threadsafe than my simple implementation), and you can use pure Mockito to mock the Factory. If this looks like it's a lot of boilerplate, it's because it is, but if you are thinking of switching to a DI solution like Guice you can cut down a lot of it.
Consider making a field or method package-private or protected and documenting that it's visible for testing purposes. Then you can insert a mocked instance in test code only.
public class InputConstraintValidator implements
ConstraintValidator<InputValidation, StringWrapper> {
Class<? extends SafeString> cvs;
public void initialize(InputValidation constraintAnnotation) {
cvs = constraintAnnotation.inputValidator();
}
public boolean isValid(StringWrapper value,
ConstraintValidatorContext context) {
SafeString instance;
try {
instance = getCvsInstance();
} catch (InstantiationException e) {
return false;
} catch (IllegalAccessException e) {
return false;
}
}
#VisibleForTesting protected getCvsInstance()
throws InstantiationException, IllegalAccessException {
return cvs.newInstance();
}
}
public class InputConstaintValidatorTest {
#Test public void testWithMockCvs() {
final SafeString cvs = mock(SafeString.class);
InputConstraintValidator validator = new InputConstraintValidator() {
#Override protected getCvsInstance() {
return cvs;
}
}
// test
}
}
I think you just need to introduce an additional mock for Class:
ArrayList<?> myListMock = mock(ArrayList.class);
Class<ArrayList> clazz = mock(Class.class);
when(clazz.newInstance()).thenReturn(myListMock);
Of course the trick is making sure your mocked clazz.newInstance() doesn't end up getting called all over the place because due to type-erasure you can't specify that it's actually a Class<ArrayList>.
Also, be careful defining your own mock for something as fundamental as ArrayList - generally I'd use a "real one" and populate it with mocks.