🏷️ Mark getState as compulsory on RandomGenerator (#733)

* 🏷️ Mark `getState` as compulsory on `RandomGenerator`

* fix tests

Author: dubzzz

src/generator/RandomGenerator.ts

@@ -16,7 +16,7 @@ export interface RandomGenerator {
   /** Jump current generator */
   unsafeJump?(): void;
   /** Access to the internal state of a RandomGenerator in a read-only fashion */
-  getState?(): readonly number[];
+  getState(): readonly number[];
 }
 
 export function unsafeGenerateN(rng: RandomGenerator, num: number): number[] {

test/unit/distribution/internals/UnsafeUniformIntDistributionInternal.spec.ts

@@ -19,6 +19,9 @@ class NatGenerator implements RandomGenerator {
     this.current = (this.current + 1) | 0;
     return previousCurrent;
   }
+  getState(): readonly number[] {
+    throw new Error('Method not implemented.');
+  }
 }
 
 const MAX_RANGE: number = 1000;