use arrov functions in upsert

Author: emilygilberts

tests/unit/test.mapreduce.js

@@ -21,9 +21,8 @@ describe('test.mapreduce.js-upsert', function () {
   it('should fulfill if the diff returns false', async function () {
     const res = await upsert({
       get: () => Promise.resolve({ _rev: 'xyz' }),
-    }, 'foo', function () {
-      return false;
-    });
+    }, 'foo', () => false
+  );
 
     res.updated.should.equal(false);
     res.rev.should.equal('xyz');
@@ -33,9 +32,8 @@ describe('test.mapreduce.js-upsert', function () {
     const res = await upsert({
       get: () => Promise.reject({ status: 404 }),
       put: () => Promise.resolve({ rev: 'abc' }),
-    }, 'foo', function () {
-      return { difference: "something" };
-    });
+    }, 'foo', () => ({ difference: "something" })
+    );
 
     res.updated.should.equal(true);
     res.rev.should.equal('abc');
@@ -46,9 +44,8 @@ describe('test.mapreduce.js-upsert', function () {
       await upsert({
         get: () => Promise.resolve({ _rev: 'xyz' }),
         put: () => Promise.reject(new Error('falala')),
-      }, 'foo', function () {
-        return { difference: "something" };
-      });
+      }, 'foo', () => ({ difference: "something" })
+      );
 
       should.fail("Expected promise to be rejected");
     } catch (err) {