Add noShrink on Arbitrary base class

dubzzz · Feb 3, 2018 · 70c2094 · 70c2094
1 parent b42e538
commit 70c2094
Show file tree

Hide file tree

Showing 2 changed files with 21 additions and 0 deletions.
diff --git a/src/check/arbitrary/definition/Arbitrary.ts b/src/check/arbitrary/definition/Arbitrary.ts
@@ -30,6 +30,17 @@ export default abstract class Arbitrary<T> {
         }
         return new MappedArbitrary(this, mapper);
     }
+    noShrink(): Arbitrary<T> {
+        class NoShrinkArbitrary extends Arbitrary<T> {
+            constructor(readonly arb: Arbitrary<T>) {
+                super();
+            }
+            generate(mrng: MutableRandomGenerator): Shrinkable<T> {
+                return new Shrinkable(this.arb.generate(mrng).value);
+            }
+        }
+        return new NoShrinkArbitrary(this);
+    }
 }
 
 abstract class ArbitraryWithShrink<T> extends Arbitrary<T> {

diff --git a/test/unit/check/arbitrary/definition/Arbitrary.spec.ts b/test/unit/check/arbitrary/definition/Arbitrary.spec.ts
@@ -74,4 +74,14 @@ describe("Arbitrary", () => {
             })
         ));
     });
+    describe('noShrink', () => {
+        it('Should remove the ability to shrink the arbitrary', () => fc.assert(
+            fc.property(fc.integer(), (seed) => {
+                const mrng = stubRng.mutable.fastincrease(seed);
+                const shrinkable = new ForwardArbitrary().noShrink().generate(mrng);
+                assert.deepStrictEqual([...shrinkable.shrink()], []);
+                return true;
+            })
+        ));
+    });
 });