Fix <Counter /> set handler (#115)

Fixes #114

I added a couple of tests to prevent this later.

Author: TrySound

.size-snapshot.json

@@ -1,18 +1,18 @@
 {
   "dist/react-powerplug.umd.js": {
-    "bundled": 23340,
-    "minified": 9379,
-    "gzipped": 2578
+    "bundled": 23769,
+    "minified": 9469,
+    "gzipped": 2596
   },
   "dist/react-powerplug.cjs.js": {
-    "bundled": 20442,
-    "minified": 10525,
-    "gzipped": 2470
+    "bundled": 20833,
+    "minified": 10881,
+    "gzipped": 2485
   },
   "dist/react-powerplug.esm.js": {
-    "bundled": 19780,
-    "minified": 9965,
-    "gzipped": 2334,
+    "bundled": 20171,
+    "minified": 10321,
+    "gzipped": 2348,
     "treeshaked": {
       "rollup": {
         "code": 365,

src/components/Counter.js

@@ -20,7 +20,7 @@ const Counter = ({ initial = 0, onChange, ...props }) => (
         dec: () => setState(add(-1)),
         incBy: value => setState(add(value)),
         decBy: value => setState(add(-value)),
-        set: value => setState(s => ({ on: set(value, s.on) })),
+        set: value => setState(s => ({ count: set(value, s.count) })),
       })
     }
   </State>

tests/components/Counter.test.js

@@ -21,6 +21,12 @@ test('<Counter />', () => {
 
   lastCallArg(renderFn).decBy(3)
   expect(renderFn).lastCalledWith(expect.objectContaining({ count: 2 }))
+
+  lastCallArg(renderFn).set(10)
+  expect(renderFn).lastCalledWith(expect.objectContaining({ count: 10 }))
+
+  lastCallArg(renderFn).set(count => count + 10)
+  expect(renderFn).lastCalledWith(expect.objectContaining({ count: 20 }))
 })
 
 test('<Counter onChange />', () => {