Adding support for mocking interfaces

Author: johanblumenberg

src/Mock.ts

@@ -18,7 +18,8 @@ export class Mocker {
     private mockableFunctionsFinder = new MockableFunctionsFinder();
     private objectPropertyCodeRetriever = new ObjectPropertyCodeRetriever();
 
-    constructor(private clazz: any, protected instance: any = {}) {
+    constructor(private clazz: any, intf: boolean, protected instance: any = {}) {
+        this.mock.__tsmockitoInterface = intf;
         this.mock.__tsmockitoInstance = this.instance;
         this.mock.__tsmockitoMocker = this;
         if (_.isObject(this.clazz) && _.isObject(this.instance)) {
@@ -40,8 +41,13 @@ export class Mocker {
             get: (target: any, name: PropertyKey) => {
                 const hasMethodStub = name in target;
                 if (!hasMethodStub) {
-                    this.createPropertyStub(name.toString());
-                    this.createInstancePropertyDescriptorListener(name.toString(), {}, this.clazz.prototype);
+                    if (this.mock.__tsmockitoInterface) {
+                        this.createMethodStub(name.toString());
+                        this.createInstanceActionListener(name.toString(), {});
+                    } else {
+                        this.createPropertyStub(name.toString());
+                        this.createInstancePropertyDescriptorListener(name.toString(), {}, this.clazz.prototype);
+                    }
                 }
                 return target[name];
             },

src/Spy.ts

@@ -8,7 +8,7 @@ export class Spy extends Mocker {
     private realMethods: { [key: string]: RealMethod };
 
     constructor(instance: any) {
-        super(instance.constructor, instance);
+        super(instance.constructor, false, instance);
 
         if (_.isObject(instance)) {
             this.processProperties(instance);

src/ts-mockito.ts

@@ -32,7 +32,18 @@ export function spy<T>(instanceToSpy: T): T {
 }
 
 export function mock<T>(clazz: { new(...args: any[]): T; } | (Function & { prototype: T }) ): T {
-    return new Mocker(clazz).getMock();
+    return new Mocker(clazz, false).getMock();
+}
+
+export function imock<T>(): T {
+    class Empty {}
+    const mockedValue = new Mocker(Empty, true).getMock();
+
+    if (typeof Proxy === "undefined") {
+        return mockedValue;
+    }
+    const tsmockitoMocker = mockedValue.__tsmockitoMocker;
+    return new Proxy(mockedValue, tsmockitoMocker.createCatchAllHandlerForRemainingPropertiesWithoutGetters());
 }
 
 export function verify<T>(method: T): MethodStubVerificator<T> {

test/mocking.types.spec.ts

@@ -1,5 +1,5 @@
 import {MethodToStub} from "../src/MethodToStub";
-import {instance, mock, when} from "../src/ts-mockito";
+import {imock, instance, mock, verify, when} from "../src/ts-mockito";
 import {Bar} from "./utils/Bar";
 
 describe("mocking", () => {
@@ -152,6 +152,51 @@ describe("mocking", () => {
 
         });
     });
+
+    describe("mocking an interface", () => {
+        let mockedFoo: SampleInterface;
+        let foo: SampleInterface;
+
+        it("can create interface mock", () => {
+            // given
+
+            // when
+            mockedFoo = imock();
+            foo = instance(mockedFoo);
+
+            // then
+        });
+
+        if (typeof Proxy !== "undefined") {
+
+            it("can verify call count", () => {
+                // given
+                mockedFoo = imock();
+                foo = instance(mockedFoo);
+
+                // when
+                const result = foo.sampleMethod();
+
+                // then
+                verify(mockedFoo.sampleMethod()).called();
+                expect(result).toBe(null);
+            });
+
+            it("can setup call actions", () => {
+                // given
+                mockedFoo = imock();
+                foo = instance(mockedFoo);
+                when(mockedFoo.sampleMethod()).thenReturn(5);
+
+                // when
+                const result = foo.sampleMethod();
+
+                // then
+                verify(mockedFoo.sampleMethod()).called();
+                expect(result).toBe(5);
+            });
+        }
+    });
 });
 
 abstract class SampleAbstractClass {