Add constructor support

Author: Brian Ojeda

index.d.ts

@@ -8,11 +8,17 @@ export type DoubledObjectWithKey<Key extends string> = {};
 
 export type TestDouble<Function> = Function;
 
+export type TestDoubleConstructor<T> = Constructor<T>;
+
 interface Call {
   context: {};
   args: any[];
 }
 
+interface Constructor<T> {
+  new (...args: any[]): T
+}
+
 export interface Captor {
   capture(): any;
   value?: any;
@@ -94,6 +100,16 @@ export function explain<T>(f: TestDouble<T>): Explanation;
 // fake: constructors
 // ----------------------------------------------------------------------------
 
+/**
+ * Create a fake object constructor the given class.
+ *
+ * @export
+ * @template T
+ * @param {{ new (...args: any[]): T }} constructor
+ * @returns {DoubledObject<T>}
+ */
+export function constructor<T>(constructor: Constructor<T>): TestDoubleConstructor<T>;
+
 //
 // fake: functions
 // ----------------------------------------------------------------------------
@@ -130,7 +146,7 @@ export { functionDouble as func };
  * @param {{ new (...args: any[]): T }} constructor
  * @returns {DoubledObject<T>}
  */
-export function object<T>(constructor: { new (...args: any[]): T }): DoubledObject<T>;
+export function object<T>(constructor: Constructor<T> ): DoubledObject<T>;
 
 /**
  * Create a fake object that has the given list of properties.

test/src/typescript/test.ts

@@ -23,9 +23,6 @@ td.when(f(td.matchers.not(false))).thenReject(new Error("rejected"));
 const fakeSum = td.function(sum);
 td.when(fakeSum(1, 2)).thenReturn(3);
 
-const fakerSum = td.function("sum");
-td.when(fakerSum(1, 2)).thenReturn(3);
-
 const fakestSum = td.function("sum");
 td.when(fakestSum(1, 2)).thenReturn(3);
 
@@ -40,7 +37,8 @@ td.when(ff(td.matchers.not(false))).thenReject(new Error("rejected"));
 
 // td.constructor()
 
-const dog = td.constructor(Dog);
+const DogFake = td.constructor(Dog);
+const dog = new DogFake()
 td.when(dog.bark()).thenReturn("bark!");
 
 // td.object()