3 files changed, 51 insertions, 4 deletions
diff --git a/pbt/ts/src/index.test.ts b/pbt/ts/src/index.test.ts
index b102fe3..f3a51e1 100644
--- a/pbt/ts/src/index.test.ts
+++ b/pbt/ts/src/index.test.ts
@@ -1,5 +1,8 @@
-import {prop_reverse_with_two_lists} from './index';
-import {Property} from './property';
+import {
+  prop_reverse_is_self_inverse,
+  prop_reverse_with_two_lists,
+} from './index';
+import {Property, classify} from './property';
 
 describe('testing lists reversal', () => {
   test('reverse of two appended lists is append of each list reversed', async () => {
@@ -8,4 +11,9 @@ describe('testing lists reversal', () => {
     );
     expect(reverse_append_result.result).toBe('OK');
   });
+  test('reverse is self-inverse', async () => {
+    const result = await Property.run(prop_reverse_is_self_inverse);
+    console.log(classify(result));
+    expect(result.result).toBe('OK');
+  });
 });
diff --git a/pbt/ts/src/index.ts b/pbt/ts/src/index.ts
index 2f59f0e..7a58ffe 100644
--- a/pbt/ts/src/index.ts
+++ b/pbt/ts/src/index.ts
@@ -63,4 +63,8 @@ export const prop_reverse_is_self_inverse = property(
   listOf(someInt),
   reverse_is_self_inverse,
   shrinklist,
+  l => {
+    const tens = Math.floor(l.length / 10);
+    return '< ' + 10 * (tens + 1);
+  },
 );
diff --git a/pbt/ts/src/property.ts b/pbt/ts/src/property.ts
index 635e731..ea7a62b 100644
--- a/pbt/ts/src/property.ts
+++ b/pbt/ts/src/property.ts
@@ -9,6 +9,7 @@ type ShrinkResult<A> = {counterexample: A; shrinks: number};
 type TestResult<A> = {
   seed: number | null;
   result: Result;
+  labels: string[];
   counterexample: ShrinkResult<A> | null;
 };
 
@@ -18,6 +19,28 @@ export type Gen<A> = (rng: Prando) => (size: number) => A;
 
 type Shrinker<A> = (a: A) => A[];
 
+/// Label test input with some arbitrary string for classification purpose
+type Label<A> = (a: A) => string;
+
+/// classify test result
+export function classify<A>(results: TestResult<A>): [number, string][] {
+  if (results.labels.length == 0) return [];
+
+  const distribution = new Map<string, number>();
+  const result: [number, string][] = [];
+  results.labels.sort();
+  results.labels.forEach(s => {
+    const num = distribution.get(s) || 0;
+    distribution.set(s, num + 1);
+  });
+
+  distribution.forEach((v, k) => {
+    result.push([(v / results.labels.length) * 100.0, k]);
+  });
+
+  return result;
+}
+
 type Property<A> = (seed: number, size: number) => Promise<TestResult<A>>;
 
 const MAX_SUCCESS = 100;
@@ -57,10 +80,13 @@ export async function property<A>(
   generator: Gen<A>,
   predicate: Predicate<A>,
   shrinker?: Shrinker<A>,
+  label?: Label<A>,
 ): Promise<Property<A>> {
   return async (seed: number, size: number) => {
     const rng = new Prando(seed);
     const gen = generator(rng);
+    const labels: string[] = [];
+
     let i = 0;
     for (; i < MAX_SUCCESS; i++) {
       const x = gen(size);
@@ -73,11 +99,20 @@ export async function property<A>(
             shrinker,
           );
         }
-        return {seed, result: 'Falsified', tests: i + 1, counterexample};
+        return {
+          seed,
+          result: 'Falsified',
+          tests: i + 1,
+          labels: [],
+          counterexample,
+        };
+      }
+      if (label !== undefined) {
+        labels.push(label(x));
       }
       size++;
     }
-    return {seed, result: 'OK', tests: i, counterexample: null};
+    return {seed, result: 'OK', tests: i, labels, counterexample: null};
   };
 }