Do not force explicitly one parameter in frequency

dubzzz · Jun 29, 2018 · 4028542 · 4028542
1 parent 1833a4b
commit 4028542
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Showing 2 changed files with 19 additions and 19 deletions.
diff --git a/src/check/arbitrary/FrequencyArbitrary.ts b/src/check/arbitrary/FrequencyArbitrary.ts
@@ -35,12 +35,17 @@ class FrequencyArbitrary<T> extends Arbitrary<T> {
 }
 
 /**
- * For one of the values generated by `warb0` or `...warbs` - the probability of selecting the ith warb is of `warb[i].weight / sum(warb[j].weight)`
- * @param warb0 One of the (Arbitrary, weight) that might be called to produce a value
- * @param warbs Other possible (Arbitrary, weight)
+ * For one of the values generated by `...warbs` - the probability of selecting the ith warb is of `warb[i].weight / sum(warb[j].weight)`
+ *
+ * **WARNING**: It expects at least one (Arbitrary, weight)
+ *
+ * @param warbs (Arbitrary, weight)s that might be called to produce a value
  */
-function frequency<T>(warb0: WeightedArbitrary<T>, ...warbs: WeightedArbitrary<T>[]): Arbitrary<T> {
-  return new FrequencyArbitrary([warb0, ...warbs]);
+function frequency<T>(...warbs: WeightedArbitrary<T>[]): Arbitrary<T> {
+  if (warbs.length === 0) {
+    throw new Error('fc.frequency expects at least one parameter');
+  }
+  return new FrequencyArbitrary([...warbs]);
 }
 
 export { frequency };
diff --git a/test/unit/check/arbitrary/FrequencyArbitrary.spec.ts b/test/unit/check/arbitrary/FrequencyArbitrary.spec.ts
@@ -14,30 +14,25 @@ describe('FrequencyArbitrary', () => {
     const rng = (seed: number) => stubRng.mutable.fastincrease(seed);
     it('Should produce the same as oneof when called on weights of 1', () =>
       fc.assert(
-        fc.property(fc.integer(), fc.integer(), fc.array(fc.integer()), (seed, choice1, others) => {
-          const gFreq = frequency(
-            { weight: 1, arbitrary: stubArb.counter(choice1) },
-            ...others.map(c => Object({ weight: 1, arbitrary: stubArb.counter(c) }))
-          ).generate(rng(seed)).value;
-          const gOneOf = oneof(stubArb.counter(choice1), ...others.map(stubArb.counter)).generate(rng(seed)).value;
+        fc.property(fc.integer(), fc.array(fc.integer(), 1, 10), (seed, choices) => {
+          const gFreq = frequency(...choices.map(c => Object({ weight: 1, arbitrary: stubArb.counter(c) }))).generate(
+            rng(seed)
+          ).value;
+          const gOneOf = oneof(...choices.map(stubArb.counter)).generate(rng(seed)).value;
           return gFreq == gOneOf;
         })
       ));
     it('Should produce the same as oneof with sum of weights elements', () =>
       fc.assert(
-        fc.property(fc.integer(), weightArb(), fc.array(weightArb()), (seed, choice1, others) => {
+        fc.property(fc.integer(), fc.array(weightArb(), 1, 10), (seed, choices) => {
           const expand = (value: number, num: number): number[] => [...Array(num)].map(() => value);
 
-          const othersOneOf = [choice1, ...others]
-            .reduce((p: number[], c) => p.concat(...expand(c[0], c[1])), [])
-            .slice(1);
+          const choicesOneOf = [...choices].reduce((p: number[], c) => p.concat(...expand(c[0], c[1])), []);
 
           const gFreq = frequency(
-            { weight: choice1[1], arbitrary: stubArb.counter(choice1[0]) },
-            ...others.map(c => Object({ weight: c[1], arbitrary: stubArb.counter(c[0]) }))
+            ...choices.map(c => Object({ weight: c[1], arbitrary: stubArb.counter(c[0]) }))
           ).generate(rng(seed)).value;
-          const gOneOf = oneof(stubArb.counter(choice1[0]), ...othersOneOf.map(stubArb.counter)).generate(rng(seed))
-            .value;
+          const gOneOf = oneof(...choicesOneOf.map(stubArb.counter)).generate(rng(seed)).value;
           return gFreq == gOneOf;
         })
       ));