Promote two-fer to core and sync to 1.2.0 (#649)

* Promote two-fer to core

And make sure we expect an optional argument, instead of passing in null, requiring boolean logic.

config.json

@@ -18,6 +18,18 @@
         "text_formatting"
       ]
     },
+    {
+      "slug": "two-fer",
+      "uuid": "7f49e997-4435-4f34-a020-bddc92c838ed",
+      "core": true,
+      "unlocked_by": null,
+      "difficulty": 1,
+      "topics": [
+        "optional_values",
+        "strings",
+        "text_formatting"
+      ]
+    },
     {
       "slug": "resistor-color",
       "uuid": "53be6837-c224-45f1-bff3-d7f74d6285ce",
@@ -223,20 +235,6 @@
         "games"
       ]
     },
-    {
-      "slug": "two-fer",
-      "uuid": "7f49e997-4435-4f34-a020-bddc92c838ed",
-      "core": false,
-      "unlocked_by": "hello-world",
-      "difficulty": 1,
-      "topics": [
-        "booleans",
-        "logic",
-        "optional_values",
-        "strings",
-        "text_formatting"
-      ]
-    },
     {
       "slug": "leap",
       "uuid": "7c8294ee-5924-4bf8-a72f-31d0e2d7d9a0",

exercises/two-fer/example.js

@@ -1,4 +1,3 @@
-export const twoFer = (name) => {
-  const nameText = name || 'you';
-  return `One for ${nameText}, one for me.`;
+export const twoFer = (name = 'you') => {
+  return `One for ${name}, one for me.`;
 };

exercises/two-fer/two-fer.spec.js

@@ -1,18 +1,15 @@
-import { twoFer } from './two-fer';
+import { twoFer } from './two-fer'
 
 describe('twoFer()', () => {
   test('no name given', () => {
-    const name = '';
-    expect(twoFer(name)).toEqual('One for you, one for me.');
-  });
+    expect(twoFer()).toEqual("One for you, one for me.")
+  })
 
   xtest('a name given', () => {
-    const name = 'Alice';
-    expect(twoFer(name)).toEqual('One for Alice, one for me.');
-  });
+    expect(twoFer("Alice")).toEqual("One for Alice, one for me.")
+  })
 
   xtest('another name given', () => {
-    const name = 'Bob';
-    expect(twoFer(name)).toEqual('One for Bob, one for me.');
-  });
-});
+    expect(twoFer("Bob")).toEqual("One for Bob, one for me.")
+  })
+})