feat(oneOf): Support maker functions as items

oneOf.js

@@ -1,9 +1,13 @@
 var hash = require('./hash')
 
-function oneOf(input, samples) {
-  return input != null && samples != null
-    ? samples[hash(input) % samples.length]
-    : oneOfCurried(input)
+function oneOf(a, b) {
+  return a != null && b != null ? oneOfMain(a, b) : oneOfCurried(a)
+}
+
+function oneOfMain(input, samples) {
+  var id = hash(input)
+  var result = samples[id % samples.length]
+  return typeof result === 'function' ? result(hash([id, 'oneOf'])) : result
 }
 
 function oneOfCurried(samples) {

tests/oneOf.test.js

@@ -0,0 +1,15 @@
+const tap = require('tap')
+const { oneOf } = require('..')
+
+tap.test('makers as items', t => {
+  const mod2 = id => id % 2
+
+  let i = -1
+
+  while (++i < 50) {
+    const result = oneOf(i, [mod2])
+    t.ok(0 <= result && result <= 1)
+  }
+
+  t.end()
+})